fortunes data file for Bash Shell Version: 1.0 Provided by: Dana French Mt Xia Technical Consulting Group 113 East Rich Norman, OK 73069 405.329.6578 dfrench@mtxia.com Specializing in Business Continuity, Disaster Recovery, AIX and HACMP % Bash Shell - Definitions These definitions are used throughout the remainder of this manual. % Bash Shell - Definitions POSIX A family of open system standards based on Unix. Bash is concerned with POSIX 1003.2, the Shell and Tools Standard. % Bash Shell - Definitions blank A space or tab character. % Bash Shell - Definitions builtin A command that is implemented internally by the shell itself, rather than by an executable program somewhere in the file system. % Bash Shell - Definitions control operator A word that performs a control function. It is a newline or one of the following: `||', `&&', `&', `;', `;;', `|', `(', or `)'. % Bash Shell - Definitions exit status The value returned by a command to its caller. The value is restricted to eight bits, so the maximum value is 255. % Bash Shell - Definitions field A unit of text that is the result of one of the shell expansions. After expansion, when executing a command, the resulting fields are used as the command name and arguments. % Bash Shell - Definitions filename A string of characters used to identify a file. % Bash Shell - Definitions job A set of processes comprising a pipeline, and any processes descended from it, that are all in the same process group. % Bash Shell - Definitions job control A mechanism by which users can selectively stop (suspend) and restart (resume) execution of processes. % Bash Shell - Definitions metacharacter A character that, when unquoted, separates words. A metacharacter is a blank or one of the following characters: `|', `&', `;', `(', `)', `<', or `>'. % Bash Shell - Definitions name A word consisting solely of letters, numbers, and underscores, and beginning with a letter or underscore. Names are used as shell variable and function names. Also referred to as an identifier. % Bash Shell - Definitions operator A control operator or a redirection operator. % Bash Shell - Definitions process group A collection of related processes each having the same process group ID. % Bash Shell - Definitions process group ID A unique identifer that represents a process group during its lifetime. % Bash Shell - Definitions reserved word A word that has a special meaning to the shell. Most reserved words introduce shell flow control constructs, such as for and while. % Bash Shell - Definitions return status A synonym for exit status. % Bash Shell - Definitions signal A mechanism by which a process may be notified by the kernel of an event occurring in the system. % Bash Shell - Definitions special builtin A shell builtin command that has been classified as special by the POSIX 1003.2 standard. % Bash Shell - Definitions token A sequence of characters considered a single unit by the shell. It is either a word or an operator. % Bash Shell - Definitions word A token that is not an operator. % Bash Shell - Basic Shell Features Bash is an acronym for `Bourne-Again SHell'. The Bourne shell is the traditional Unix shell originally written by Stephen Bourne. All of the Bourne shell builtin commands are available in Bash, and the rules for evaluation and quoting are taken from the POSIX 1003.2 specification for the `standard' Unix shell. % Bash Shell - Escape Character A non-quoted backslash `\' is the Bash escape character. It preserves the literal value of the next character that follows, with the exception of newline. If a \newline pair appears, and the backslash itself is not quoted, the \newline is treated as a line continuation (that is, it is removed from the input stream and effectively ignored). % Bash Shell - Single Quotes Enclosing characters in single quotes (`'') preserves the literal value of each character within the quotes. A single quote may not occur between single quotes, even when preceded by a backslash. % Bash Shell - Double Quotes Enclosing characters in double quotes (`"') preserves the literal value of all characters within the quotes, with the exception of `$', ``', and `\'. The characters `$' and ``' retain their special meaning within double quotes . The backslash retains its special meaning only when followed by one of the following characters: `$', ``', `"', `\', or newline. Within double quotes, backslashes that are followed by one of these characters are removed. Backslashes preceding characters without a special meaning are left unmodified. A double quote may be quoted within double quotes by preceding it with a backslash. % Bash Shell - ANSI-C Quoting Words of the form $'string' are treated specially. The word expands to string, with backslash-escaped characters replaced as specified by the ANSI C standard. Backslash escape sequences, if present, are decoded as follows: \a - alert (bell) \b - backspace \e - an escape character (not ANSI C) \f - form feed \n - newline \r - carriage return \t - horizontal tab \v - vertical tab \\ - backslash \' - single quote \nnn - the eight-bit character whose value is the octal value nnn (one to three digits) \xHH - the eight-bit character whose value is the hexadecimal value HH (one or two hex digits) \cx - a control-x character The expanded result is single-quoted, as if the dollar sign had not been present. % Bash Shell - Locale-Specific Translation A double-quoted string preceded by a dollar sign (`$') will cause the string to be translated according to the current locale. If the current locale is C or POSIX, the dollar sign is ignored. If the string is translated and replaced, the replacement is double-quoted. Some systems use the message catalog selected by the LC_MESSAGES shell variable. Others create the name of the message catalog from the value of the TEXTDOMAIN shell variable, possibly adding a suffix of `.mo'. If you use the TEXTDOMAIN variable, you may need to set the TEXTDOMAINDIR variable to the location of the message catalog files. Still others use both variables in this fashion: TEXTDOMAINDIR/LC_MESSAGES/LC_MESSAGES/TEXTDOMAIN.mo. % Bash Shell - Simple Commands A simple command is the kind of command encountered most often. It's just a sequence of words separated by blanks, terminated by one of the shell's control operators. The first word generally specifies a command to be executed, with the rest of the words being that command's arguments. The return status of a simple command is its exit status as provided by the POSIX 1003.1 waitpid function, or 128+n if the command was terminated by signal n. % Bash Shell - Pipelines A pipeline is a sequence of simple commands separated by `|'. The format for a pipeline is [time [-p]] [!] command1 [| command2 ...] The output of each command in the pipeline is connected via a pipe to the input of the next command. That is, each command reads the previous command's output. The reserved word time causes timing statistics to be printed for the pipeline once it finishes. The statistics currently consist of elapsed (wall-clock) time and user and system time consumed by the command's execution. The `-p' option changes the output format to that specified by POSIX. The TIMEFORMAT variable may be set to a format string that specifies how the timing information should be displayed. The use of time as a reserved word permits the timing of shell builtins, shell functions, and pipelines. An external time command cannot time these easily. If the pipeline is not executed asynchronously, the shell waits for all commands in the pipeline to complete. Each command in a pipeline is executed in its own subshell. The exit status of a pipeline is the exit status of the last command in the pipeline. If the reserved word `!' precedes the pipeline, the exit status is the logical negation of the exit status of the last command. % Bash Shell - Lists of Commands A list is a sequence of one or more pipelines separated by one of the operators `;', `&', `&&', or `||', and optionally terminated by one of `;', `&', or a newline. Of these list operators, `&&' and `||' have equal precedence, followed by `;' and `&', which have equal precedence. A sequence of one or more newlines may appear in a list to delimit commands, equivalent to a semicolon. % Bash Shell - Lists of Commands If a command is terminated by the control operator `&', the shell executes the command asynchronously in a subshell. This is known as executing the command in the background. The shell does not wait for the command to finish, and the return status is 0 (true). When job control is not active, the standard input for asynchronous commands, in the absence of any explicit redirections, is redirected from /dev/null. % Bash Shell - Lists of Commands Commands separated by a `;' are executed sequentially; the shell waits for each command to terminate in turn. The return status is the exit status of the last command executed. % Bash Shell - Lists of Commands The control operators `&&' and `||' denote AND lists and OR lists, respectively. An AND list has the form command1 && command2 command2 is executed if, and only if, command1 returns an exit status of zero. An OR list has the form command1 || command2 command2 is executed if, and only if, command1 returns a non-zero exit status. The return status of AND and OR lists is the exit status of the last command executed in the list. % Bash Shell - Looping Constructs until The syntax of the until command is: until test-commands; do consequent-commands; done Execute consequent-commands as long as test-commands has an exit status which is not zero. The return status is the exit status of the last command executed in consequent-commands, or zero if none was executed. % Bash Shell - Looping Constructs while The syntax of the while command is: while test-commands; do consequent-commands; done Execute consequent-commands as long as test-commands has an exit status of zero. The return status is the exit status of the last command executed in consequent- commands, or zero if none was executed. % Bash Shell - Looping Constructs for The syntax of the for command is: for name [in words ...]; do commands; done Expand words, and execute commands once for each member in the resultant list, with name bound to the current member. If `in words' is not present, the for command executes the commands once for each positional parameter that is set, as if `in "$@"' had been specified. The return status is the exit status of the last command that executes. If there are no items in the expansion of words, no commands are executed, and the return status is zero. % Bash Shell - Looping Constructs An alternate form of the for command is also supported: for (( expr1 ; expr2 ; expr3 )) ; do commands ; done First, the arithmetic expression expr1 is evaluated according to the rules described below. The arithmetic expression expr2 is then evaluated repeatedly until it evaluates to zero. Each time expr2 evaluates to a non-zero value, commands are executed and the arithmetic expression expr3 is evaluated. If any expression is omitted, it behaves as if it evaluates to 1. The return value is the exit status of the last command in list that is executed, or false if any of the expressions is invalid. The break and continue builtins may be used to control loop execution. % Bash Shell - Conditional Constructs - if The syntax of the if command is: if test-commands; then consequent-commands; [elif more-test-commands; then more-consequents;] [else alternate-consequents;] fi The test-commands list is executed, and if its return status is zero, the consequent- commands list is executed. If test-commands returns a non-zero status, each elif list is executed in turn, and if its exit status is zero, the corresponding more-consequents is executed and the command completes. If `else alternate- consequents' is present, and the final command in the final if or elif clause has a non-zero exit status, then alternate-consequents is executed. The return status is the exit status of the last command executed, or zero if no condition tested true. % Bash Shell - Conditional Constructs - case The syntax of the case command is: case word in [ [(] pattern [| pattern]...) command-list ;;]... esac case will selectively execute the command-list corresponding to the first pattern that matches word. The `|' is used to separate multiple patterns, and the `)' operator terminates a pattern list. A list of patterns and an associated command-list is known as a clause. Each clause must be terminated with `;;'. The word undergoes tilde expansion, parameter expansion, command substitution, arithmetic expansion, and quote removal before matching is attempted. Each pattern undergoes tilde expansion, parameter expansion, command substitution, and arithmetic expansion. There may be an arbitrary number of case clauses, each terminated by a `;;'. The first pattern that matches determines the command-list that is executed. % Bash Shell - Conditional Constructs - case Here is an example using case in a script that could be used to describe one interesting feature of an animal: echo -n "Enter the name of an animal: " read ANIMAL echo -n "The $ANIMAL has " case $ANIMAL in horse | dog | cat) echo -n "four";; man | kangaroo ) echo -n "two";; *) echo -n "an unknown number of";; esac echo " legs." The return status is zero if no pattern is matched. Otherwise, the return status is the exit status of the command-list executed. % Bash Shell - Conditional Constructs - select The select construct allows the easy generation of menus. It has almost the same syntax as the for command: select name [in words ...]; do commands; done The list of words following in is expanded, generating a list of items. The set of expanded words is printed on the standard error output stream, each preceded by a number. If the `in words' is omitted, the positional parameters are printed, as if `in "$@"' had been specifed. The PS3 prompt is then displayed and a line is read from the standard input. If the line consists of a number corresponding to one of the displayed words, then the value of name is set to that word. If the line is empty, the words and prompt are displayed again. If EOF is read, the select command completes. Any other value read causes name to be set to null. The line read is saved in the variable REPLY. The commands are executed after each selection until a break command is executed, at which point the select command completes. % Bash Shell - Conditional Constructs - select Here is an example that allows the user to pick a filename from the current directory, and displays the name and index of the file selected. select fname in *; do echo you picked $fname \($REPLY\) break; done % Bash Shell - Conditional Constructs - math (( expression )) The arithmetic expression is evaluated according to the rules described below. If the value of the expression is non-zero, the return status is 0; otherwise the return status is 1. This is exactly equivalent to let "expression" % Bash Shell - Conditional Expressions [[ expression ]] Conditional Expressions. Word splitting and filename expansion are not performed on the words between the `[[' and `]]'; tilde expansion, parameter and variable expansion, arithmetic expansion, command substitution, process substitution, and quote removal are performed. % Bash Shell - Conditional Expressions When the `==' and `!=' operators are used, the string to the right of the operator is considered a pattern and matched according to the rules described below in 3.5.8.1 % Bash Shell - Conditional Expressions - Pattern Matching The return value is 0 if the string matches or does not match the pattern, respectively, and 1 otherwise. Any part of the pattern may be quoted to force it to be matched as a string. % Bash Shell - Conditional Expressions Expressions may be combined using the following operators, listed in decreasing order of precedence: ( expression ) Returns the value of expression. This may be used to override the normal precedence of operators. % Bash Shell - Conditional Expressions ! expression True if expression is false. % Bash Shell - Conditional Expressions expression1 && expression2 True if both expression1 and expression2 are true. % Bash Shell - Conditional Expressions expression1 || expression2 True if either expression1 or expression2 is true. The && and || operators do not evaluate expression2 if the value of expression1 is sufficient to determine the return value of the entire conditional expression. % Bash Shell - Grouping Commands Bash provides two ways to group a list of commands to be executed as a unit. When commands are grouped, redirections may be applied to the entire command list. For example, the output of all the commands in the list may be redirected to a single stream. ( list ) Placing a list of commands between parentheses causes a subshell to be created, and each of the commands in list to be executed in that subshell. Since the list is executed in a subshell, variable assignments do not remain in effect after the subshell completes. The exit status of this construct is the exit status of list. % Bash Shell - Grouping Commands { list; } Placing a list of commands between curly braces causes the list to be executed in the current shell context. No subshell is created. The semicolon (or newline) following list is required. In addition to the creation of a subshell, there is a subtle difference between these two constructs due to historical reasons. The braces are reserved words, so they must be separated from the list by blanks. The parentheses are operators, and are recognized as separate tokens by the shell even if they are not separated from the list by whitespace. The exit status of this construct is the exit status of list. % Bash Shell - Shell Functions Shell functions are a way to group commands for later execution using a single name for the group. They are executed just like a "regular" command. When the name of a shell function is used as a simple command name, the list of commands associated with that function name is executed. Shell functions are executed in the current shell context; no new process is created to interpret them. % Bash Shell - Shell Functions Functions are declared using this syntax: [ function ] name () { command-list; } This defines a shell function named name. The reserved word function is optional. If the function reserved word is supplied, the parentheses are optional. The body of the function is the command-list between { and }. This list is executed whenever name is specified as the name of a command. The exit status of a function is the exit status of the last command executed in the body. % Bash Shell - Shell Functions [ function ] name () { command-list; } Note that for historical reasons, the curly braces that surround the body of the function must be separated from the body by blanks or newlines. This is because the braces are reserved words and are only recognized as such when they are separated by whitespace. Also, the command- list must be terminated with a semicolon or a newline. % Bash Shell - Shell Functions When a function is executed, the arguments to the function become the positional parameters during its execution. The special parameter `#' that expands to the number of positional parameters is updated to reflect the change. Positional parameter 0 is unchanged. The FUNCNAME variable is set to the name of the function while the function is executing. % Bash Shell - Shell Functions If the builtin command return is executed in a function, the function completes and execution resumes with the next command after the function call. When a function completes, the values of the positional parameters and the special parameter `#' are restored to the values they had prior to the function's execution. If a numeric argument is given to return, that is the function's return status; otherwise the function's return status is the exit status of the last command executed before the return. % Bash Shell - Shell Functions Variables local to the function may be declared with the local builtin. These variables are visible only to the function and the commands it invokes. % Bash Shell - Shell Functions Functions may be recursive. No limit is placed on the number of recursive calls. % Bash Shell - Positional Parameters A positional parameter is a parameter denoted by one or more digits, other than the single digit 0. Positional parameters are assigned from the shell's arguments when it is invoked, and may be reassigned using the set builtin command. Positional parameter N may be referenced as ${N}, or as $N when N consists of a single digit. Positional parameters may not be assigned to with assignment statements. The set and shift builtins are used to set and unset them. The positional parameters are temporarily replaced when a shell function is executed. When a positional parameter consisting of more than a single digit is expanded, it must be enclosed in braces. % Bash Shell - Special Parameters * Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, it expands to a single word with the value of each parameter separated by the first character of the IFS special variable. That is, "$*" is equivalent to "$1c$2c...", where c is the first character of the value of the IFS variable. If IFS is unset, the parameters are separated by spaces. If IFS is null, the parameters are joined without intervening separators. % Bash Shell - Special Parameters @ Expands to the positional parameters, starting from one. When the expansion occurs within double quotes, each parameter expands to a separate word. That is, "$@" is equivalent to "$1" "$2" .... When there are no positional parameters, "$@" and $@ expand to nothing (i.e., they are removed). % Bash Shell - Special Parameters # Expands to the number of positional parameters in decimal. % Bash Shell - Special Parameters ? Expands to the exit status of the most recently executed foreground pipeline. - (A hyphen.) Expands to the current option flags as specified upon invocation, by the set builtin command, or those set by the shell itself (such as the `-i' option). % Bash Shell - Special Parameters $ Expands to the process ID of the shell. In a () subshell, it expands to the process ID of the invoking shell, not the subshell. % Bash Shell - Special Parameters ! Expands to the process ID of the most recently executed background (asynchronous) command. % Bash Shell - Special Parameters 0 Expands to the name of the shell or shell script. This is set at shell initialization. If Bash is invoked with a file of commands, $0 is set to the name of that file. If Bash is started with the `-c' option, then $0 is set to the first argument after the string to be executed, if one is present. Otherwise, it is set to the filename used to invoke Bash, as given by argument zero. % Bash Shell - Special Parameters _ (An underscore.) At shell startup, set to the absolute filename of the shell or shell script being executed as passed in the argument list. Subsequently, expands to the last argument to the previous command, after expansion. Also set to the full pathname of each command executed and placed in the environment exported to that command. When checking mail, this parameter holds the name of the mail file. % Bash Shell - Shell Expansions Expansion is performed on the command line after it has been split into tokens. There are seven kinds of expansion performed: * brace expansion * tilde expansion * parameter and variable expansion * command substitution * arithmetic expansion * word splitting * filename expansion % Bash Shell - Brace Expansion Brace expansion is a mechanism by which arbitrary strings may be generated. This mechanism is similar to filename expansion, but the file names generated need not exist. Patterns to be brace expanded take the form of an optional preamble, followed by a series of comma-separated strings between a pair of braces, followed by an optional postscript. The preamble is prefixed to each string contained within the braces, and the postscript is then appended to each resulting string, expanding left to right. % Bash Shell - Brace Expansion Brace expansions may be nested. The results of each expanded string are not sorted; left to right order is preserved. For example, $ echo a{d,c,b}e ade ace abe % Bash Shell - Brace Expansion Brace expansion is performed before any other expansions, and any characters special to other expansions are preserved in the result. It is strictly textual. Bash does not apply any syntactic interpretation to the context of the expansion or the text between the braces. To avoid conflicts with parameter expansion, the string `${' is not considered eligible for brace expansion. % Bash Shell - Brace Expansion A correctly-formed brace expansion must contain unquoted opening and closing braces, and at least one unquoted comma. Any incorrectly formed brace expansion is left unchanged. % Bash Shell - Brace Expansion This construct is typically used as shorthand when the common prefix of the strings to be generated is longer than in the above example: mkdir /usr/local/src/bash/{old,new,dist,bugs} or chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}} % Bash Shell - Tilde Expansion If a word begins with an unquoted tilde character (`~'), all of the characters up to the first unquoted slash (or all characters, if there is no unquoted slash) are considered a tilde-prefix. If none of the characters in the tilde-prefix are quoted, the characters in the tilde-prefix following the tilde are treated as a possible login name. If this login name is the null string, the tilde is replaced with the value of the HOME shell variable. If HOME is unset, the home directory of the user executing the shell is substituted instead. Otherwise, the tilde-prefix is replaced with the home directory associated with the specified login name. % Bash Shell - Tilde Expansion If the tilde-prefix is `~+', the value of the shell variable PWD replaces the tilde-prefix. If the tilde-prefix is `~-', the value of the shell variable OLDPWD, if it is set, is substituted. % Bash Shell - Tilde Expansion If the characters following the tilde in the tilde-prefix consist of a number N, optionally prefixed by a `+' or a `-', the tilde-prefix is replaced with the corresponding element from the directory stack, as it would be displayed by the dirs builtin invoked with the characters following tilde in the tilde-prefix as an argument. If the tilde-prefix, sans the tilde, consists of a number without a leading `+' or `-', `+' is assumed. If the login name is invalid, or the tilde expansion fails, the word is left unchanged. % Bash Shell - Tilde Expansion Each variable assignment is checked for unquoted tilde-prefixes immediately following a `:' or `='. In these cases, tilde expansion is also performed. Consequently, one may use file names with tildes in assignments to PATH, MAILPATH, and CDPATH, and the shell assigns the expanded value. % Bash Shell - Shell Parameter Expansion The `$' character introduces parameter expansion, command substitution, or arithmetic expansion. The parameter name or symbol to be expanded may be enclosed in braces, which are optional but serve to protect the variable to be expanded from characters immediately following it which could be interpreted as part of the name. When braces are used, the matching ending brace is the first `}' not escaped by a backslash or within a quoted string, and not within an embedded arithmetic expansion, command substitution, or parameter expansion. % Bash Shell - Shell Parameter Expansion The basic form of parameter expansion is ${parameter}. The value of parameter is substituted. The braces are required when parameter is a positional parameter with more than one digit, or when parameter is followed by a character that is not to be interpreted as part of its name. % Bash Shell - Shell Parameter Expansion If the first character of a parameter is an exclamation point, a level of variable indirection is introduced. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself. This is known as indirect expansion. The exception to this is the expansion of ${!prefix*} described below. % Bash Shell - Shell Parameter Expansion When not performing substring expansion, Bash tests for a parameter that is unset or null; omitting the colon results in a test only for a parameter that is unset. Put another way, if the colon is included, the operator tests for both existence and that the value is not null; if the colon is omitted, the operator tests only for existence. % Bash Shell - Shell Parameter Expansion ${parameter:-word} If parameter is unset or null, the expansion of word is substituted. Otherwise, the value of parameter is substituted. % Bash Shell - Shell Parameter Expansion ${parameter:=word} If parameter is unset or null, the expansion of word is assigned to parameter. The value of parameter is then substituted. Positional parameters and special parameters may not be assigned to in this way. % Bash Shell - Shell Parameter Expansion ${parameter:?word} If parameter is null or unset, the expansion of word (or a message to that effect if word is not present) is written to the standard error and the shell, if it is not interactive, exits. Otherwise, the value of parameter is substituted. % Bash Shell - Shell Parameter Expansion ${parameter:+word} If parameter is null or unset, nothing is substituted, otherwise the expansion of word is substituted. % Bash Shell - Shell Parameter Expansion ${parameter:offset} ${parameter:offset:length} Expands to up to length characters of parameter starting at the character specified by offset. If length is omitted, expands to the substring of parameter starting at the character specified by offset. length and offset are arithmetic expressions. This is referred to as Substring Expansion. length must evaluate to a number greater than or equal to zero. If offset evaluates to a number less than zero, the value is used as an offset from the end of the value of parameter. If parameter is `@', the result is length positional parameters beginning at offset. If parameter is an array name indexed by `@' or `*', the result is the length members of the array beginning with ${parameter[offset]}. Substring indexing is zero-based unless the positional parameters are used, in which case the indexing starts at 1. % Bash Shell - Shell Parameter Expansion ${!prefix*} Expands to the names of variables whose names begin with prefix, separated by the first character of the IFS special variable. % Bash Shell - Shell Parameter Expansion ${#parameter} The length in characters of the expanded value of parameter is substituted. If parameter is `*' or `@', the value substituted is the number of positional parameters. If parameter is an array name subscripted by `*' or `@', the value substituted is the number of elements in the array. % Bash Shell - Shell Parameter Expansion ${parameter#word} ${parameter##word} The word is expanded to produce a pattern just as in filename expansion. If the pattern matches the beginning of the expanded value of parameter, then the result of the expansion is the expanded value of parameter with the shortest matching pattern (the `#' case) or the longest matching pattern (the `##' case) deleted. If parameter is `@' or `*', the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with `@' or `*', the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list. % Bash Shell - Shell Parameter Expansion ${parameter%word} ${parameter%%word} The word is expanded to produce a pattern just as in filename expansion. If the pattern matches a trailing portion of the expanded value of parameter, then the result of the expansion is the value of parameter with the shortest matching pattern (the `%' case) or the longest matching pattern (the `%%' case) deleted. If parameter is `@' or `*', the pattern removal operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with `@' or `*', the pattern removal operation is applied to each member of the array in turn, and the expansion is the resultant list. % Bash Shell - Shell Parameter Expansion ${parameter/pattern/string} ${parameter//pattern/string} The pattern is expanded to produce a pattern just as in filename expansion. Parameter is expanded and the longest match of pattern against its value is replaced with string. In the first form, only the first match is replaced. The second form causes all matches of pattern to be replaced with string. If pattern begins with `#', it must match at the beginning of the expanded value of parameter. If pattern begins with `%', it must match at the end of the expanded value of parameter. If string is null, matches of pattern are deleted and the / following pattern may be omitted. If parameter is `@' or `*', the substitution operation is applied to each positional parameter in turn, and the expansion is the resultant list. If parameter is an array variable subscripted with `@' or `*', the substitution operation is applied to each member of the array in turn, and the expansion is the resultant list. % Bash Shell - Command Substitution Command substitution allows the output of a command to replace the command itself. Command substitution occurs when a command is enclosed as follows: $(command) or `command` Bash performs the expansion by executing command and replacing the command substitution with the standard output of the command, with any trailing newlines deleted. Embedded newlines are not deleted, but they may be removed during word splitting. The command substitution $(cat file) can be replaced by the equivalent but faster $(< file). % Bash Shell - Command Substitution When the old-style backquote form of command substitution is used, backslash retains its literal meaning except when followed by `$', ``', or `\'. The first backquote not preceded by a backslash terminates the command substitution. When using the $(command) form, all characters between the parentheses make up the command; none are treated specially. % Bash Shell - Command Substitution Command substitutions may be nested. To nest when using the backquoted form, escape the inner backquotes with backslashes. If the substitution appears within double quotes, word splitting and filename expansion are not performed on the results. % Bash Shell - Arithmetic Expansion Arithmetic expansion allows the evaluation of an arithmetic expression and the substitution of the result. The format for arithmetic expansion is: $(( expression )) The expression is treated as if it were within double quotes, but a double quote inside the parentheses is not treated specially. All tokens in the expression undergo parameter expansion, command substitution, and quote removal. Arithmetic substitutions may be nested. If the expression is invalid, Bash prints a message indicating failure to the standard error and no substitution occurs. % Bash Shell - Process Substitution Process substitution is supported on systems that support named pipes (FIFOs) or the `/dev/fd' method of naming open files. It takes the form of <(list) or >(list) The process list is run with its input or output connected to a FIFO or some file in `/dev/fd'. The name of this file is passed as an argument to the current command as the result of the expansion. If the >(list) form is used, writing to the file will provide input for list. If the <(list) form is used, the file passed as an argument should be read to obtain the output of list. Note that no space may appear between the < or > and the left parenthesis, otherwise the construct would be interpreted as a redirection. % Bash Shell - Process Substitution When available, process substitution is performed simultaneously with parameter and variable expansion, command substitution, and arithmetic expansion. % Bash Shell - Word Splitting The shell scans the results of parameter expansion, command substitution, and arithmetic expansion that did not occur within double quotes for word splitting. % Bash Shell - Word Splitting The shell treats each character of $IFS as a delimiter, and splits the results of the other expansions into words on these characters. If IFS is unset, or its value is exactly , the default, then any sequence of IFS characters serves to delimit words. If IFS has a value other than the default, then sequences of the whitespace characters space and tab are ignored at the beginning and end of the word, as long as the whitespace character is in the value of IFS (an IFS whitespace character). Any character in IFS that is not IFS whitespace, along with any adjacent IFS whitespace characters, delimits a field. A sequence of IFS whitespace characters is also treated as a delimiter. If the value of IFS is null, no word splitting occurs. % Bash Shell - Word Splitting Explicit null arguments ("" or ") are retained. Unquoted implicit null arguments, resulting from the expansion of parameters that have no values, are removed. If a parameter with no value is expanded within double quotes, a null argument results and is retained. Note that if no expansion occurs, no splitting is performed. % Bash Shell - Filename Expansion Bash scans each word for the characters `*', `?', and `['. If one of these characters appears, then the word is regarded as a pattern, and replaced with an alphabetically sorted list of file names matching the pattern. If no matching file names are found, and the shell option nullglob is disabled, the word is left unchanged. If the nullglob option is set, and no matches are found, the word is removed. If the shell option nocaseglob is enabled, the match is performed without regard to the case of alphabetic characters. % Bash Shell - Filename Expansion When a pattern is used for filename generation, the character `.' at the start of a filename or immediately following a slash must be matched explicitly, unless the shell option dotglob is set. % Bash Shell - Filename Expansion The GLOBIGNORE shell variable may be used to restrict the set of filenames matching a pattern. % Bash Shell - Filename Expansion If GLOBIGNORE is set, each matching filename that also matches one of the patterns in % Bash Shell - Filename Expansion GLOBIGNORE is removed from the list of matches. The filenames `.' and `..' are always ignored, even when GLOBIGNORE is set. However, setting GLOBIGNORE has the effect of enabling the dotglob shell option, so all other filenames beginning with a `.' will match. To get the old behavior of ignoring filenames beginning with a `.', make `.*' one of the patterns in GLOBIGNORE. The dotglob option is disabled when GLOBIGNORE is unset. % Bash Shell - Pattern Matching Any character that appears in a pattern, other than the special pattern characters described below, matches itself. The NUL character may not occur in a pattern. The special pattern characters must be quoted if they are to be matched literally. % Bash Shell - Pattern Matching * Matches any string, including the null string. % Bash Shell - Pattern Matching ? Matches any single character. % Bash Shell - Pattern Matching [...] Matches any one of the enclosed characters. A pair of characters separated by a hyphen denotes a range expression; any character that sorts between those two characters, inclusive, using the current locale's collating sequence and character set, is matched. If the first character following the `[' is a `!' or a `^' then any character not enclosed is matched. A `-' may be matched by including it as the first or last character in the set. A `]' may be matched by including it as the first character in the set. The sorting order of characters in range expressions is determined by the current locale and the value of the LC_COLLATE shell variable, if set. % Bash Shell - Pattern Matching In the default C locale, `[a-dx-z]' is equivalent to `[abcdxyz]'. Many locales sort characters in dictionary order, and in these locales `[a-dx-z]' is typically not equivalent to `[abcdxyz]'; it might be equivalent to `[aBbCcDdxXyYz]', for example. To obtain the traditional interpretation of ranges in bracket expressions, you can force the use of the C locale by setting the LC_COLLATE or LC_ALL environment variable to the value `C'. % Bash Shell - Pattern Matching Within `[' and `]', character classes can be specified using the syntax [:class:], where class is one of the following classes defined in the POSIX 1003.2 standard: alnum alpha ascii blank cntrl digit graph lower print punct space upper word xdigit A character class matches any character belonging to that class. The word character class matches letters, digits, and the character `_'. % Bash Shell - Pattern Matching Within `[' and `]', an equivalence class can be specified using the syntax [=c=], which matches all characters with the same collation weight (as defined by the current locale) as the character c. Within `[' and `]', the syntax [.symbol.] matches the collating symbol symbol. % Bash Shell - Pattern Matching If the extglob shell option is enabled using the shopt builtin, several extended pattern matching operators are recognized. In the following description, a pattern-list is a list of one or more patterns separated by a `|'. % Bash Shell - Pattern Matching ?(pattern-list) Matches zero or one occurrence of the given patterns. % Bash Shell - Pattern Matching *(pattern-list) Matches zero or more occurrences of the given patterns. % Bash Shell - Pattern Matching +(pattern-list) Matches one or more occurrences of the given patterns. % Bash Shell - Pattern Matching @(pattern-list) Matches exactly one of the given patterns. % Bash Shell - Pattern Matching !(pattern-list) Matches anything except one of the given patterns. % Bash Shell - Quote Removal After the preceding expansions, all unquoted occurrences of the characters `\', `'', and `"' that did not result from one of the above expansions are removed. % Bash Shell - Redirections ls > dirlist 2>&1 directs both standard output (file descriptor 1) and standard error (file descriptor 2) to the file dirlist, while the command % Bash Shell - Redirections ls 2>&1 > dirlist directs only the standard output to file dirlist, because the standard error was duplicated as standard output before the standard output was redirected to dirlist. % Bash Shell - Redirections /dev/fd/fd If fd is a valid integer, file descriptor fd is duplicated. % Bash Shell - Redirections /dev/stdin File descriptor 0 is duplicated. % Bash Shell - Redirections /dev/stdout File descriptor 1 is duplicated. % Bash Shell - Redirections /dev/stderr File descriptor 2 is duplicated. % Bash Shell - Redirections /dev/tcp/host/port If host is a valid hostname or Internet address, and port is an integer port number or service name, Bash attempts to open a TCP connection to the corresponding socket. % Bash Shell - Redirections /dev/udp/host/port If host is a valid hostname or Internet address, and port is an integer port number or service name, Bash attempts to open a UDP connection to the corresponding socket. % Bash Shell - Redirecting Input Redirection of input causes the file whose name results from the expansion of word to be opened for reading on file descriptor n, or the standard input (file descriptor 0) if n is not specified. The general format for redirecting input is: [n][|]word % Bash Shell - Redirecting Output If the redirection operator is `>', and the noclobber option to the set builtin has been enabled, the redirection will fail if the file whose name results from the expansion of word exists and is a regular file. If the redirection operator is `>|', or the redirection operator is `>' and the noclobber option is not enabled, the redirection is attempted even if the file named by word exists. % Bash Shell - Appending Redirected Output Redirection of output in this fashion causes the file whose name results from the expansion of word to be opened for appending on file descriptor n, or the standard output (file descriptor 1) if n is not specified. If the file does not exist it is created. The general format for appending output is: [n] >>word % Bash Shell - Redirecting Standard Output and Standard Error Bash allows both the standard output (file descriptor 1) and the standard error output (file descriptor 2) to be redirected to the file whose name is the expansion of word with this construct. There are two formats for redirecting standard output and standard error: &>word and >&word Of the two forms, the first is preferred. This is semantically equivalent to >word 2>&1 % Bash Shell - Here Documents This type of redirection instructs the shell to read input from the current source until a line containing only word (with no trailing blanks) is seen. All of the lines read up to that point are then used as the standard input for a command. The format of here-documents is: <<[-]word here-document delimiter % Bash Shell - Here Documents <<[-]word here-document delimiter No parameter expansion, command substitution, arithmetic expansion, or filename expansion is performed on word. If any characters in word are quoted, the delimiter is the result of quote removal on word, and the lines in the here-document are not expanded. If word is unquoted, all lines of the here-document are subjected to parameter expansion, command substitution, and arithmetic expansion. In the latter case, the character sequence \newline is ignored, and `\' must be used to quote the characters `\', `$', and ``'. % Bash Shell - Here Documents <<[-]word here-document delimiter If the redirection operator is `<<-', then all leading tab characters are stripped from input lines and the line containing delimiter. This allows here-documents within shell scripts to be indented in a natural fashion. % Bash Shell - Here Strings A variant of here documents, the format is: <<&word is used similarly to duplicate output file descriptors. If n is not specified, the standard output (file descriptor 1) is used. If the digits in word do not specify a file descriptor open for output, a redirection error occurs. As a special case, if n is omitted, and word does not expand to one or more digits, the standard output and standard error are redirected as described previously. % Bash Shell - Moving File Descriptors The redirection operator [n]<&digit- moves the file descriptor digit to file descriptor n, or the standard input (file descriptor 0) if n is not specified. digit is closed after being duplicated to n. % Bash Shell - Moving File Descriptors The redirection operator [n]>&digit- moves the file descriptor digit to file descriptor n, or the standard output (file descriptor 1) if n is not specified. % Bash Shell - Opening File Descriptors for Reading and Writing The redirection operator [n]<>word causes the file whose name is the expansion of word to be opened for both reading and writing on file descriptor n, or on file descriptor 0 if n is not specified. If the file does not exist, it is created. % Bash Shell - Simple Command Expansion When a simple command is executed, the shell performs the following expansions, assignments, and redirections, from left to right. Step 1. The words that the parser has marked as variable assignments (those preceding the command name) and redirections are saved for later processing. Step 2. The words that are not variable assignments or redirections are expanded. If any words remain after expansion, the first word is taken to be the name of the command and the remaining words are the arguments. Step 3. Redirections are performed as described above. Step 4. The text after the `=' in each variable assignment undergoes tilde expansion, parameter expansion, command substitution, arithmetic expansion, and quote removal before being assigned to the variable. % Bash Shell - Command Search and Execution After a command has been split into words, if it results in a simple command and an optional list of arguments, the 6 steps are taken. Step 1. If the command name contains no slashes, the shell attempts to locate it. If there exists a shell function by that name, that function is invoked as described in 3.3 Shell Functions. % Bash Shell - Command Search and Execution Step 2. If the name does not match a function, the shell searches for it in the list of shell builtins. % Bash Shell - Command Search and Execution If a match is found, that builtin is invoked. Step 3. If the name is neither a shell function nor a builtin, and contains no slashes, Bash searches each element of $PATH for a directory containing an executable file by that name. Bash uses a hash table to remember the full pathnames of executable files to avoid multiple PATH searches. A full search of the directories in $PATH is performed only if the command is not found in the hash table. If the search is unsuccessful, the shell prints an error message and returns an exit status of 127. % Bash Shell - Command Search and Execution Step 4. If the search is successful, or if the command name contains one or more slashes, the shell executes the named program in a separate execution environment. Argument 0 is set to the name given, and the remaining arguments to the command are set to the arguments supplied, if any. % Bash Shell - Command Search and Execution Step 5. If this execution fails because the file is not in executable format, and the file is not a directory, it is assumed to be a shell script and the shell executes it as described in 3.8 Shell Scripts. % Bash Shell - Command Search and Execution Step 6. If the command was not begun asynchronously, the shell waits for the command to complete and collects its exit status. % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * open files inherited by the shell at invocation, as modified by redirections supplied to the exec builtin % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * the current working directory as set by cd, pushd, or popd, or inherited by the shell at invocation % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * the file creation mode mask as set by umask or inherited from the shell's parent % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * current traps set by trap % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * shell parameters that are set by variable assignment or with set or inherited from the shell's parent in the environment % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * shell functions defined during execution or inherited from the shell's parent in the environment % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * options enabled at invocation (either by default or with command-line arguments) or by set % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * options enabled by shopt % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * shell aliases defined with alias % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * various process IDs, including those of background jobs, the value of $$, and the value of $PPID When a simple command other than a builtin or shell function is to be executed, it is invoked in a separate execution environment that consists of the following. Unless otherwise noted, the values are inherited from the shell. % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * the shell's open files, plus any modifications and additions specified by redirections to the command % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * the current working directory % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * the file creation mode mask % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * shell variables marked for export, along with variables exported for the command, passed in the environment % Bash Shell - Command Execution Environment The shell has an execution environment, one component of which is the following: * traps caught by the shell are reset to the values inherited from the shell's parent, and traps ignored by the shell are ignored A command invoked in this separate environment cannot affect the shell's execution environment. % Bash Shell - Command Execution Environment Command substitution and asynchronous commands are invoked in a subshell environment that is a duplicate of the shell environment, except that traps caught by the shell are reset to the values that the shell inherited from its parent at invocation. Builtin commands that are invoked as part of a pipeline are also executed in a subshell environment. Changes made to the subshell environment cannot affect the shell's execution environment. % Bash Shell - Command Execution Environment If a command is followed by a `&' and job control is not active, the default standard input for the command is the empty file `/dev/null'. Otherwise, the invoked command inherits the file descriptors of the calling shell as modified by redirections. % Bash Shell - Environment When a program is invoked it is given an array of strings called the environment. This is a list of name-value pairs, of the form name=value. % Bash Shell - Environment Bash provides several ways to manipulate the environment. On invocation, the shell scans its own environment and creates a parameter for each name found, automatically marking it for export to child processes. Executed commands inherit the environment. The export and `declare -x' commands allow parameters and functions to be added to and deleted from the environment. If the value of a parameter in the environment is modified, the new value becomes part of the environment, replacing the old. The environment inherited by any executed command consists of the shell's initial environment, whose values may be modified in the shell, less any pairs removed by the unset and `export -n' commands, plus any additions via the export and `declare -x' commands. % Bash Shell - Environment The environment for any simple command or function may be augmented temporarily by prefixing it with parameter assignments, as described in 3.4 Shell Parameters. These assignment statements affect only the environment seen by that command. % Bash Shell - Environment If the `-k' option is set, then all parameter assignments are placed in the environment for a command, not just those that precede the command name. % Bash Shell - Environment When Bash invokes an external command, the variable `$_' is set to the full path name of the command and passed to that command in its environment. % Bash Shell - Exit Status For the shell's purposes, a command which exits with a zero exit status has succeeded. A non- zero exit status indicates failure. This seemingly counter-intuitive scheme is used so there is one well-defined way to indicate success and a variety of ways to indicate various failure modes. % Bash Shell - Exit Status When a command terminates on a fatal signal whose number is N, Bash uses the value 128+N as the exit status. % Bash Shell - Exit Status If a command is not found, the child process created to execute it returns a status of 127. If a command is found but is not executable, the return status is 126. % Bash Shell - Exit Status If a command fails because of an error during expansion or redirection, the exit status is greater than zero. % Bash Shell - Exit Status The exit status is used by the Bash conditional commands and some of the list constructs. % Bash Shell - Exit Status All of the Bash builtins return an exit status of zero if they succeed and a non-zero status on failure, so they may be used by the conditional and list constructs. All builtins return an exit status of 2 to indicate incorrect usage. % Bash Shell - Signals When Bash is interactive, in the absence of any traps, it ignores SIGTERM (so that `kill 0' does not kill an interactive shell), and SIGINT is caught and handled (so that the wait builtin is interruptible). When Bash receives a SIGINT, it breaks out of any executing loops. In all cases, Bash ignores SIGQUIT. If job control is in effect, Bash ignores SIGTTIN, SIGTTOU, and SIGTSTP. % Bash Shell - Signals Commands started by Bash have signal handlers set to the values inherited by the shell from its parent. When job control is not in effect, asynchronous commands ignore SIGINT and SIGQUIT as well. Commands run as a result of command substitution ignore the keyboard- generated job control signals SIGTTIN, SIGTTOU, and SIGTSTP. % Bash Shell - Signals The shell exits by default upon receipt of a SIGHUP. Before exiting, an interactive shell resends the SIGHUP to all jobs, running or stopped. Stopped jobs are sent SIGCONT to ensure that they receive the SIGHUP. To prevent the shell from sending the SIGHUP signal to a particular job, it should be removed from the jobs table with the disown builtin or marked to not receive SIGHUP using disown -h. % Bash Shell - Signals If the huponexit shell option has been set with shopt, Bash sends a SIGHUP to all jobs when an interactive login shell exits. % Bash Shell - Signals When Bash receives a signal for which a trap has been set while waiting for a command to complete, the trap will not be executed until the command completes. When Bash is waiting for an asynchronous command via the wait builtin, the reception of a signal for which a trap has been set will cause the wait builtin to return immediately with an exit status greater than 128, immediately after which the trap is executed. % Bash Shell - Shell Scripts A shell script is a text file containing shell commands. When such a file is used as the first non- option argument when invoking Bash, and neither the `-c' nor `-s' option is supplied, Bash reads and executes commands from the file, then exits. This mode of operation creates a non-interactive shell. The shell first searches for the file in the current directory, and looks in the directories in $PATH if not found there. % Bash Shell - Shell Scripts When Bash runs a shell script, it sets the special parameter 0 to the name of the file, rather than the name of the shell, and the positional parameters are set to the remaining arguments, if any are given. If no additional arguments are supplied, the positional parameters are unset. % Bash Shell - Shell Scripts A shell script may be made executable by using the chmod command to turn on the execute bit. % Bash Shell - Shell Scripts When Bash finds such a file while searching the $PATH for a command, it spawns a subshell to execute it. In other words, executing filename arguments is equivalent to executing bash filename arguments if filename is an executable shell script. This subshell reinitializes itself, so that the effect is as if a new shell had been invoked to interpret the script, with the exception that the locations of commands remembered by the parent are retained by the child. % Bash Shell - Shell Scripts Most versions of Unix make this a part of the operating system's command execution mechanism. If the first line of a script begins with the two characters `#!', the remainder of the line specifies an interpreter for the program. Thus, you can specify Bash, awk, Perl, or some other interpreter and write the rest of the script file in that language. % Bash Shell - Shell Scripts The arguments to the interpreter consist of a single optional argument following the interpreter name on the first line of the script file, followed by the name of the script file, followed by the rest of the arguments. Bash will perform this action on operating systems that do not handle it themselves. Note that some older versions of Unix limit the interpreter name and argument to a maximum of 32 characters. % Bash Shell - Shell Scripts Bash scripts often begin with #! /bin/bash (assuming that Bash has been installed in `/bin'), since this ensures that Bash will be used to interpret the script, even if it is executed under another shell. % Bash Shell - Bourne Shell Builtins The following shell builtin commands are inherited from the Bourne Shell. These commands are implemented as specified by the POSIX 1003.2 standard. : (a colon) : [arguments] Do nothing beyond expanding arguments and performing redirections. The return status is zero. % Bash Shell - Bourne Shell Builtins . (a period) . filename [arguments] Read and execute commands from the filename argument in the current shell context. If filename does not contain a slash, the PATH variable is used to find filename. When Bash is not in POSIX mode, the current directory is searched if filename is not found in $PATH. If any arguments are supplied, they become the positional parameters when filename is executed. Otherwise the positional parameters are unchanged. The return status is the exit status of the last command executed, or zero if no commands are executed. If filename is not found, or cannot be read, the return status is non-zero. This builtin is equivalent to source. % Bash Shell - Bourne Shell Builtins break break [n] Exit from a for, while, until, or select loop. If n is supplied, the nth enclosing loop is exited. n must be greater than or equal to 1. The return status is zero unless n is not greater than or equal to 1. % Bash Shell - Bourne Shell Builtins cd cd [-L|-P] [directory] Change the current working directory to directory. If directory is not given, the value of the HOME shell variable is used. If the shell variable CDPATH exists, it is used as a search path. If directory begins with a slash, CDPATH is not used. The `-P' option means to not follow symbolic links; symbolic links are followed by default or with the `-L' option. If directory is `-', it is equivalent to $OLDPWD. The return status is zero if the directory is successfully changed, non-zero otherwise. % Bash Shell - Bourne Shell Builtins continue continue [n] Resume the next iteration of an enclosing for, while, until, or select loop. If n is supplied, the execution of the nth enclosing loop is resumed. n must be greater than or equal to 1. The return status is zero unless n is not greater than or equal to 1. % Bash Shell - Bourne Shell Builtins eval eval [arguments] The arguments are concatenated together into a single command, which is then read and executed, and its exit status returned as the exit status of eval. If there are no arguments or only empty arguments, the return status is zero. % Bash Shell - Bourne Shell Builtins exec exec [-cl] [-aname] [command [arguments] ] If command is supplied, it replaces the shell without creating a new process. If the `- l' option is supplied, the shell places a dash at the beginning of the zeroth arg passed to command. This is what the login program does. The `-c' option causes command to be executed with an empty environment. If `-a' is supplied, the shell passes name as the zeroth argument to command. If no command is specified, redirections may be used to affect the current shell environment. If there are no redirection errors, the return status is zero; otherwise the return status is non-zero. % Bash Shell - Bourne Shell Builtins exit exit [n] Exit the shell, returning a status of n to the shell's parent. If n is omitted, the exit status is that of the last command executed. Any trap on EXIT is executed before the shell terminates. % Bash Shell - Bourne Shell Builtins export export [-fn] [-p] [name[=value] ] Mark each name to be passed to child processes in the environment. If the `-f' option is supplied, the names refer to shell functions; otherwise the names refer to shell variables. The `-n' option means to no longer mark each name for export. If no names are supplied, or if the `-p' option is given, a list of exported names is displayed. The `-p' option displays output in a form that may be reused as input. The return status is zero unless an invalid option is supplied, one of the names is not a valid shell variable name, or `-f' is supplied with a name that is not a shell function. % Bash Shell - Bourne Shell Builtins getopts getopts optstring name [args] getopts is used by shell scripts to parse positional parameters. optstring contains the option characters to be recognized; if a character is followed by a colon, the option is expected to have an argument, which should be separated from it by white space. The colon (`:') and question mark (`?') may not be used as option characters. Each time it is invoked, getopts places the next option in the shell variable name, initializing name if it does not exist, and the index of the next argument to be processed into the variable OPTIND. OPTIND is initialized to 1 each time the shell or a shell script is invoked. When an option requires an argument, getopts places that argument into the variable OPTARG. The shell does not reset OPTIND automatically; it must be manually reset between multiple calls to getopts within the same shell invocation if a new set of parameters is to be used. % Bash Shell - Bourne Shell Builtins - getopts When the end of options is encountered, getopts exits with a return value greater than zero. OPTIND is set to the index of the first non-option argument, and name is set to `?'. getopts normally parses the positional parameters, but if more arguments are given in args, getopts parses those instead. getopts can report errors in two ways. If the first character of optstring is a colon, silent error reporting is used. In normal operation diagnostic messages are printed when invalid options or missing option arguments are encountered. If the variable OPTERR is set to 0, no error messages will be displayed, even if the first character of optstring is not a colon. % Bash Shell - Bourne Shell Builtins - getopts If an invalid option is seen, getopts places `?' into name and, if not silent, prints an error message and unsets OPTARG. If getopts is silent, the option character found is placed in OPTARG and no diagnostic message is printed. % Bash Shell - Bourne Shell Builtins - getopts If a required argument is not found, and getopts is not silent, a question mark (`?') is placed in name, OPTARG is unset, and a diagnostic message is printed. If getopts is silent, then a colon (`:') is placed in name and OPTARG is set to the option character found. % Bash Shell - Bourne Shell Builtins hash hash [-'r] [-p filename] [-dt] [name] Remember the full pathnames of commands specified as name arguments, so they need not be searched for on subsequent invocations. The commands are found by searching through the directories listed in $PATH. The `-p' option inhibits the path search, and filename is used as the location of name. The `-r' option causes the shell to forget all remembered locations. The `-d' option causes the shell to forget the remembered location of each name. If the `-t' option is supplied, the full pathname to which each name corresponds is printed. If multiple name arguments are supplied with `-t' the name is printed before the hashed full pathname. The `-l' option causes output to be displayed in a format that may be reused as input. If no arguments are given, or if only `-l' is supplied, information about remembered commands is printed. The return status is zero unless a name is not found or an invalid option is supplied. % Bash Shell - Bourne Shell Builtins pwd pwd [-LP] Print the absolute pathname of the current working directory. If the `-P' option is supplied, the pathname printed will not contain symbolic links. If the `-L' option is supplied, the pathname printed may contain symbolic links. The return status is zero unless an error is encountered while determining the name of the current directory or an invalid option is supplied. % Bash Shell - Bourne Shell Builtins readonly readonly [-apf] [name] ... Mark each name as readonly. The values of these names may not be changed by subsequent assignment. If the `-f' option is supplied, each name refers to a shell function. The `-a' option means each name refers to an array variable. If no name arguments are given, or if the `-p' option is supplied, a list of all readonly names is printed. The `-p' option causes output to be displayed in a format that may be reused as input. The return status is zero unless an invalid option is supplied, one of the name arguments is not a valid shell variable or function name, or the `-f' option is supplied with a name that is not a shell function. % Bash Shell - Bourne Shell Builtins return return [n] Cause a shell function to exit with the return value n. If n is not supplied, the return value is the exit status of the last command executed in the function. This may also be used to terminate execution of a script being executed with the . (or source) builtin, returning either n or the exit status of the last command executed within the script as the exit status of the script. The return status is non-zero if return is used outside a function and not during the execution of a script by . or source. % Bash Shell - Bourne Shell Builtins shift shift [n] Shift the positional parameters to the left by n. The positional parameters from n+1 ... $# are renamed to $1 ... $#-n+1. Parameters represented by the numbers $# to n+1 are unset. n must be a non-negative number less than or equal to $#. If n is zero or greater than $#, the positional parameters are not changed. If n is not supplied, it is assumed to be 1. The return status is zero unless n is greater than $# or less than zero, non-zero otherwise. % Bash Shell - Bourne Shell Builtins test [ Evaluate a conditional expression expr. Each operator and operand must be a separate argument. Expressions are composed of the primaries described below in 6.4 Bash Conditional Expressions. When the [ form is used, the last argument to the command must be a ]. Expressions may be combined using the following operators, listed in decreasing order of precedence. % Bash Shell - Bourne Shell Builtins ! expr True if expr is false. % Bash Shell - Bourne Shell Builtins ( expr ) Returns the value of expr. This may be used to override the normal precedence of operators. % Bash Shell - Bourne Shell Builtins expr1 -a expr2 True if both expr1 and expr2 are true. % Bash Shell - Bourne Shell Builtins expr1 -o expr2 True if either expr1 or expr2 is true. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 0 arguments The expression is false. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 1 argument The expression is true if and only if the argument is not null. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 2 arguments If the first argument is `!', the expression is true if and only if the second argument is null. If the first argument is one of the unary conditional operators, the expression is true if the unary test is true. If the first argument is not a valid unary operator, the expression is false. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 3 arguments If the second argument is one of the binary conditional operators, the result of the expression is the result of the binary test using the first and third arguments as operands. If the first argument is `!', the value is the negation of the two-argument test using the second and third arguments. If the first argument is exactly `(' and the third argument is exactly `)', the result is the one- argument test of the second argument. Otherwise, the expression is false. The `-a' and `-o' operators are considered binary operators in this case. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 4 arguments If the first argument is `!', the result is the negation of the three-argument expression composed of the remaining arguments. Otherwise, the expression is parsed and evaluated according to precedence using the rules listed above. % Bash Shell - Bourne Shell Builtins - test The test and [ builtins evaluate conditional expressions using a set of rules based on the number of arguments. 5 or more arguments The expression is parsed and evaluated according to precedence using the rules listed above. % Bash Shell - Bourne Shell Builtins times times Print out the user and system times used by the shell and its children. The return status is zero. % Bash Shell - Bourne Shell Builtins - trap trap trap [-lp] [arg] [sigspec...] The commands in arg are to be read and executed when the shell receives signal sigspec. If arg is absent or equal to `-', all specified signals are reset to the values they had when the shell was started. If arg is the null string, then the signal specified by each sigspec is ignored by the shell and commands it invokes. If arg is not present and `-p' has been supplied, the shell displays the trap commands associated with each sigspec. If no arguments are supplied, or only `-p' is given, trap prints the list of commands associated with each signal number in a form that may be reused as shell input. Each sigspec is either a signal name such as SIGINT (with or without the SIG prefix) or a signal number. If a sigspec is 0 or EXIT, arg is executed when the shell exits. If a sigspec is DEBUG, the command arg is executed after every simple command. % Bash Shell - Bourne Shell Builtins - trap trap trap [-lp] [arg] [sigspec...] If a sigspec is ERR, the command arg is executed whenever a simple command has a non-zero exit status. The ERR trap is not executed if the failed command is part of an until or while loop, part of an if statement, part of a && or || list, or if the command's return status is being inverted using !. The `-l' option causes the shell to print a list of signal names and their corresponding numbers. % Bash Shell - Bourne Shell Builtins - trap trap trap [-lp] [arg] [sigspec...] Signals ignored upon entry to the shell cannot be trapped or reset. Trapped signals are reset to their original values in a child process when it is created. % Bash Shell - Bourne Shell Builtins - trap trap trap [-lp] [arg] [sigspec...] The return status is zero unless a sigspec does not specify a valid signal. % Bash Shell - Bourne Shell Builtins - umask umask umask [-p] [-S] [mode] Set the shell process's file creation mask to mode. If mode begins with a digit, it is interpreted as an octal number; if not, it is interpreted as a symbolic mode mask similar to that accepted by the chmod command. If mode is omitted, the current value of the mask is printed. If the `-S' option is supplied without a mode argument, the mask is printed in a symbolic format. If the `-p' option is supplied, and mode is omitted, the output is in a form that may be reused as input. The return status is zero if the mode is successfully changed or if no mode argument is supplied, and non-zero otherwise. % Bash Shell - Bourne Shell Builtins - umask umask umask [-p] [-S] [mode] Note that when the mode is interpreted as an octal number, each number of the umask is subtracted from 7. Thus, a umask of 022 results in permissions of 755. % Bash Shell - Bourne Shell Builtins unset unset [-fv] [name] Each variable or function name is removed. If no options are supplied, or the `-v' option is given, each name refers to a shell variable. If the `-f' option is given, the names refer to shell functions, and the function definition is removed. Readonly variables and functions may not be unset. The return status is zero unless a name does not exist or is readonly. % Bash Shell - Bash Builtin Commands alias alias [-p] [name[=value]...] Without arguments or with the `-p' option, alias prints the list of aliases on the standard output in a form that allows them to be reused as input. If arguments are supplied, an alias is defined for each name whose value is given. If no value is given, the name and value of the alias is printed. Aliases are described in 6.6 Aliases. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command Display current Readline key and function bindings, bind a key sequence to a Readline function or macro, or set a Readline variable. Each non-option argument is a command as it would appear in a a Readline initialization file, but each binding or command must be passed as a separate argument; e.g., `"\C-x\C-r":re-read-init- file'. Options, if supplied, have the following meanings: % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -m keymap Use keymap as the keymap to be affected by the subsequent bindings. Acceptable keymap names are emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi- move, vi-command, and vi-insert. vi is equivalent to vi-command; emacs is equivalent to emacs-standard. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -l List the names of all Readline functions. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -p Display Readline function names and bindings in such a way that they can be used as input or in a Readline initialization file. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -P List current Readline function names and bindings. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -v Display Readline variable names and values in such a way that they can be used as input or in a Readline initialization file. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -V List current Readline variable names and values. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -s Display Readline key sequences bound to macros and the strings they output in such a way that they can be used as input or in a Readline initialization file. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -S Display Readline key sequences bound to macros and the strings they output. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -f filename Read key bindings from filename. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -q function Query about which keys invoke the named function. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -u function Unbind all keys bound to the named function. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -r keyseq Remove any current binding for keyseq. % Bash Shell - Bash Builtin Commands - bind bind [-m keymap] [-lpsvPSV] bind [-m keymap] [-q function] [-u function] [-r keyseq] bind [-m keymap] -f filename bind [-m keymap] -x keyseq:shell-command bind [-m keymap] keyseq:function-name bind readline-command -x keyseq:shell-command Cause shell-command to be executed whenever keyseq is entered. % Bash Shell - Bash Builtin Commands builtin [shell-builtin [args]] Run a shell builtin, passing it args, and return its exit status. This is useful when defining a shell function with the same name as a shell builtin, retaining the functionality of the builtin within the function. The return status is non-zero if shell-builtin is not a shell builtin command. % Bash Shell - Bash Builtin Commands command command [-pVv]command [arguments...] Runs command with arguments ignoring any shell function named command. Only shell builtin commands or commands found by searching the PATH are executed. If there is a shell function named ls, running `command ls' within the function will execute the external command ls instead of calling the function recursively. The `-p' option means to use a default value for PATH that is guaranteed to find all of the standard utilities. The return status in this case is 127 if command cannot be found or an error occurred, and the exit status of command otherwise. % Bash Shell - Bash Builtin Commands command command [-pVv]command [arguments...] If either the `-V' or `-v' option is supplied, a description of command is printed. % Bash Shell - Bash Builtin Commands command command [-pVv]command [arguments...] The `-v' option causes a single word indicating the command or file name used to invoke command to be displayed; the `-V' option produces a more verbose description. In this case, the return status is zero if command is found, and non-zero if not. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] Declare variables and give them attributes. If no names are given, then display the values of variables instead. The `-p' option will display the attributes and values of each name. When `-p' is used, additional options are ignored. The `-F' option inhibits the display of function definitions; only the function name and attributes are printed. `-F' implies `-f'. The following options can be used to restrict output to variables with the specified attributes or to give variables attributes: % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -a Each name is an array variable. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -f Use function names only. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -i The variable is to be treated as an integer; arithmetic evaluation is performed when the variable is assigned a value. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -r Make names readonly. These names cannot then be assigned values by subsequent assignment statements or unset. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -t Give each name the trace attribute. Traced functions inherit the DEBUG trap from the calling shell. The trace attribute has no special meaning for variables. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] -x Mark each name for export to subsequent commands via the environment. % Bash Shell - Bash Builtin Commands - declare declare declare [-afFirtx] [-p] [name[=value]] The return status is zero unless an invalid option is encountered, an attempt is made to define a function using `-f foo=bar', an attempt is made to assign a value to a readonly variable, an attempt is made to assign a value to an array variable without using the compound assignment syntax, one of the names is not a valid shell variable name, an attempt is made to turn off readonly status for a readonly variable, an attempt is made to turn off array status for an array variable, or an attempt is made to display a non-existent function with `-f'. % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] Output the args, separated by spaces, terminated with a newline. The return status is always 0. If `-n' is specified, the trailing newline is suppressed. If the `-e' option is given, interpretation of the following backslash-escaped characters is enabled. The `- E' option disables the interpretation of these escape characters, even on systems where they are interpreted by default. The xpg_echo shell option may be used to dynamically determine whether or not echo expands these escape characters by default. echo interprets the following escape sequences: % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \a alert (bell) % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \b backspace % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \c suppress trailing newline % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \e escape % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \f form feed % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \n new line % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \r carriage return % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \t horizontal tab % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \v vertical tab % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \\ backslash % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \0nnn the eight-bit character whose value is the octal value nnn (zero to three octal digits) % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \nnn the eight-bit character whose value is the octal value nnn (one to three octal digits) % Bash Shell - Bash Builtin Commands - echo echo echo [-neE] [arg...] \xHH the eight-bit character whose value is the hexadecimal value HH (one or two hex digits) enable % Bash Shell - Bash Builtin Commands - enable enable [-n] [-p] [-f filename] [-ads] [name ...] Enable and disable builtin shell commands. Disabling a builtin allows a disk command which has the same name as a shell builtin to be executed without specifying a full pathname, even though the shell normally searches for builtins before disk commands. If `-n' is used, the names become disabled. Otherwise names are enabled. For example, to use the test binary found via $PATH instead of the shell builtin version, type `enable -n test'. % Bash Shell - Bash Builtin Commands - enable enable [-n] [-p] [-f filename] [-ads] [name ...] If the `-p' option is supplied, or no name arguments appear, a list of shell builtins is printed. With no other arguments, the list consists of all enabled shell builtins. The `- a' option means to list each builtin with an indication of whether or not it is enabled. % Bash Shell - Bash Builtin Commands - enable enable [-n] [-p] [-f filename] [-ads] [name ...] The `-f' option means to load the new builtin command name from shared object filename, on systems that support dynamic loading. The `-d' option will delete a builtin loaded with `-f'. % Bash Shell - Bash Builtin Commands - enable enable [-n] [-p] [-f filename] [-ads] [name ...] If there are no options, a list of the shell builtins is displayed. The `-s' option restricts enable to the POSIX special builtins. If `-s' is used with `-f', the new builtin becomes a special builtin. % Bash Shell - Bash Builtin Commands - enable enable [-n] [-p] [-f filename] [-ads] [name ...] The return status is zero unless a name is not a shell builtin or there is an error loading a new builtin from a shared object. % Bash Shell - Bash Builtin Commands - help help help [-s] [pattern] Display helpful information about builtin commands. If pattern is specified, help gives detailed help on all commands matching pattern, otherwise a list of the builtins is printed. The `-s' option restricts the information displayed to a short usage synopsis. The return status is zero unless no command matches pattern. % Bash Shell - Bash Builtin Commands let expression [expression] The let builtin allows arithmetic to be performed on shell variables. Each expression is evaluated according to the rules given below in 6.5 Shell Arithmetic. If the last expression evaluates to 0, let returns 1; otherwise 0 is returned. local % Bash Shell - Bash Builtin Commands local [option] name[=value] For each argument, a local variable named name is created, and assigned value. The option can be any of the options accepted by declare. local can only be used within a function; it makes the variable name have a visible scope restricted to that function and its children. The return status is zero unless local is used outside a function, an invalid name is supplied, or name is a readonly variable. % Bash Shell - Bash Builtin Commands logout logout [n] Exit a login shell, returning a status of n to the shell's parent. % Bash Shell - Bash Builtin Commands printf printf format [arguments] Write the formatted arguments to the standard output under the control of the format. % Bash Shell - Bash Builtin Commands printf printf format [arguments] The format is a character string which contains three types of objects: plain characters, which are simply copied to standard output, character escape sequences, which are converted and copied to the standard output, and format specifications, each of which causes printing of the next successive argument. In addition to the standard printf(1) formats, `%b' causes printf to expand backslash escape sequences in the corresponding argument, and `%q' causes printf to output the corresponding argument in a format that can be reused as shell input. % Bash Shell - Bash Builtin Commands printf printf format [arguments] The format is reused as necessary to consume all of the arguments. If the format requires more arguments than are supplied, the extra format specifications behave as if a zero value or null string, as appropriate, had been supplied. The return value is zero on success, non-zero on failure. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] One line is read from the standard input, or from the file descriptor fd supplied as an argument to the `-u' option, and the first word is assigned to the first name, the second word to the second name, and so on, with leftover words and their intervening separators assigned to the last name. If there are fewer words read from the input stream than names, the remaining names are assigned empty values. The characters in the value of the IFS variable are used to split the line into words. The backslash character `\' may be used to remove any special meaning for the next character read and for line continuation. If no names are supplied, the line read is assigned to the variable REPLY. The return code is zero, unless end-of-file is encountered, read times out, or an invalid file descriptor is supplied as the argument to `-u'. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -a aname The words are assigned to sequential indices of the array variable aname, starting at 0. All elements are removed from aname before the assignment. Other name arguments are ignored. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -d delim The first character of delim is used to terminate the input line, rather than newline. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -e Readline is used to obtain the line. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -n nchars read returns after reading nchars characters rather than waiting for a complete line of input. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -p prompt Display prompt, without a trailing newline, before attempting to read any input. The prompt is displayed only if input is coming from a terminal. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -r If this option is given, backslash does not act as an escape character. The backslash is considered to be part of the line. In particular, a backslash-newline pair may not be used as a line continuation. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -s Silent mode. If input is coming from a terminal, characters are not echoed. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -t timeout Cause read to time out and return failure if a complete line of input is not read within timeout seconds. This option has no effect if read is not reading input from the terminal or a pipe. % Bash Shell - Bash Builtin Commands - read read read [-ers] [-a aname] [-d delim] [-n nchars] [-p prompt] [-t timeout] [-u fd] [name ...] -u fd Read input from file descriptor fd. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] Toggle the values of variables controlling optional shell behavior. With no options, or with the `-p' option, a list of all settable options is displayed, with an indication of whether or not each is set. The `-p' option causes output to be displayed in a form that may be reused as input. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] -s Enable (set) each optname. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] -u Disable (unset) each optname. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] -q Suppresses normal output; the return status indicates whether the optname is set or unset. If multiple optname arguments are given with `-q', the return status is zero if all optnames are enabled; non-zero otherwise. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] -o Restricts the values of optname to be those defined for the `-o' option to the set builtin. % Bash Shell - Bash Builtin Commands - shopt shopt shopt [-pqsu] [-o] [optname ...] If either `-s' or `-u' is used with no optname arguments, the display is limited to those options which are set or unset, respectively. Unless otherwise noted, the shopt options are disabled (off) by default. The return status when listing options is zero if all optnames are enabled, non-zero otherwise. When setting or unsetting options, the return status is zero unless an optname is not a valid shell option. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] cdable_vars If this is set, an argument to the cd builtin command that is not a directory is assumed to be the name of a variable whose value is the directory to change to. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] cdspell If set, minor errors in the spelling of a directory component in a cd command will be corrected. The errors checked for are transposed characters, a missing character, and a character too many. If a correction is found, the corrected path is printed, and the command proceeds. This option is only used by interactive shells. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] checkhash If this is set, Bash checks that a command found in the hash table exists before trying to execute it. If a hashed command no longer exists, a normal path search is performed. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] checkwinsize If set, Bash checks the window size after each command and, if necessary, updates the values of LINES and COLUMNS. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] cmdhist If set, Bash attempts to save all lines of a multiple-line command in the same history entry. This allows easy re-editing of multi-line commands. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] dotglob If set, Bash includes filenames beginning with a `.' in the results of filename expansion. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] execfail If this is set, a non-interactive shell will not exit if it cannot execute the file specified as an argument to the exec builtin command. An interactive shell does not exit if exec fails. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] expand_aliases If set, aliases are expanded as described below under Aliases, 6.6 Aliases. This option is enabled by default for interactive shells. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] extglob If set, the extended pattern matching features described above are enabled. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] histappend If set, the history list is appended to the file named by the value of the HISTFILE variable when the shell exits, rather than overwriting the file. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] histreedit If set, and Readline is being used, a user is given the opportunity to re-edit a failed history substitution. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] histverify If set, and Readline is being used, the results of history substitution are not immediately passed to the shell parser. Instead, the resulting line is loaded into the Readline editing buffer, allowing further modification. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] hostcomplete If set, and Readline is being used, Bash will attempt to perform hostname completion when a word containing a `@' is being completed. This option is enabled by default. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] huponexit If set, Bash will send SIGHUP to all jobs when an interactive login shell exits. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] interactive_comments Allow a word beginning with `#' to cause that word and all remaining characters on that line to be ignored in an interactive shell. This option is enabled by default. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] lithist If enabled, and the cmdhist option is enabled, multi-line commands are saved to the history with embedded newlines rather than using semicolon separators where possible. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] login_shell The shell sets this option if it is started as a login shell. The value may not be changed. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] mailwarn If set, and a file that Bash is checking for mail has been accessed since the last time it was checked, the message "The mail in mailfile has been read" is displayed. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] no_empty_cmd_completion If set, and Readline is being used, Bash will not attempt to search the PATH for possible completions when completion is attempted on an empty line. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] nocaseglob If set, Bash matches filenames in a case-insensitive fashion when performing filename expansion. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] nullglob If set, Bash allows filename patterns which match no files to expand to a null string, rather than themselves. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] progcomp If set, the programmable completion facilities are enabled. This option is enabled by default. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] promptvars If set, prompt strings undergo variable and parameter expansion after being expanded. This option is enabled by default. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] restricted_shell The shell sets this option if it is started in restricted mode. The value may not be changed. This is not reset when the startup files are executed, allowing the startup files to discover whether or not a shell is restricted. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] shift_verbose If this is set, the shift builtin prints an error message when the shift count exceeds the number of positional parameters. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] sourcepath If set, the source builtin uses the value of PATH to find the directory containing the file supplied as an argument. This option is enabled by default. % Bash Shell - Bash Builtin Commands - shopt options shopt [-pqsu] [-o] [optname ...] xpg_echo If set, the echo builtin expands backslash-escape sequences by default. The return status when listing options is zero if all optnames are enabled, non-zero otherwise. When setting or unsetting options, the return status is zero unless an optname is not a valid shell option. % Bash Shell - Bash Builtin Commands source source filename A synonym for .. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] For each name, indicate how it would be interpreted if used as a command name. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] If the `-t' option is used, type prints a single word which is one of `alias', `function', `builtin', `file' or `keyword', if name is an alias, shell function, shell builtin, disk file, or shell reserved word, respectively. If the name is not found, then nothing is printed, and type returns a failure status. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] If the `-p' option is used, type either returns the name of the disk file that would be executed, or nothing if `-t' would not return `file'. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] The `-P' option forces a path search for each name, even if `-t' would not return `file'. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] If a command is hashed, `-p' and `-P' print the hashed value, not necessarily the file that appears first in $PATH. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] If the `-a' option is used, type returns all of the places that contain an executable named file. This includes aliases and functions, if and only if the `-p' option is not also used. % Bash Shell - Bash Builtin Commands - type type type [-afptP] [name ...] If the `-f' option is used, type does not attempt to find shell functions, as with the command builtin. The return status is zero if any of the names are found, non-zero if none are found. typeset % Bash Shell - Bash Builtin Commands typeset [-afFrxi] [-p] [name[=value]] The typeset command is supplied for compatibility with the Korn shell; however, it has been deprecated in favor of the declare builtin command. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] ulimit provides control over the resources available to processes started by the shell, on systems that allow such control. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -S Change and report the soft limit associated with a resource. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -H Change and report the hard limit associated with a resource. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -a All current limits are reported. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -c The maximum size of core files created. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -d The maximum size of a process's data segment. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -f The maximum size of files created by the shell. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -l The maximum size that may be locked into memory. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -m The maximum resident set size. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -n The maximum number of open file descriptors. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -p The pipe buffer size. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -s The maximum stack size. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -t The maximum amount of cpu time in seconds. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -u The maximum number of processes available to a single user. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] -v The maximum amount of virtual memory available to the process. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] If limit is given, it is the new value of the specified resource; the special limit values hard, soft, and unlimited stand for the current hard limit, the current soft limit, and no limit, respectively. Otherwise, the current value of the soft limit for the specified resource is printed, unless the `-H' option is supplied. When setting new limits, if neither `-H' nor `-S' is supplied, both the hard and soft limits are set. If no option is given, then `-f' is assumed. Values are in 1024-byte increments, except for `-t', which is in seconds, `-p', which is in units of 512-byte blocks, and `-n' and `- u', which are unscaled values. % Bash Shell - Bash Builtin Commands - ulimit ulimit ulimit [-acdflmnpstuvSH] [limit] The return status is zero unless an invalid option or argument is supplied, or an error occurs while setting a new limit. % Bash Shell - Bash Builtin Commands - unalias unalias unalias [-a] [name ... ] Remove each name from the list of aliases. If `-a' is supplied, all aliases are removed. Aliases are described in 6.6 Aliases. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] If no options or arguments are supplied, set displays the names and values of all shell variables and functions, sorted according to the current locale, in a format that may be reused as input. When options are supplied, they set or unset shell attributes. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -a Mark variables and function which are modified or created for export to the environment of subsequent commands. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -b Cause the status of terminated background jobs to be reported immediately, rather than before printing the next primary prompt. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -e Exit immediately if a simple command exits with a non-zero status, unless the command that fails is part of an until or while loop, part of an if statement, part of a && or || list, or if the command's return status is being inverted using !. A trap on ERR, if set, is executed before the shell exits. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -f Disable file name generation (globbing). % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -h Locate and remember (hash) commands as they are looked up for execution. This option is enabled by default. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -k All arguments in the form of assignment statements are placed in the environment for a command, not just those that precede the command name. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -m Job control is enabled. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -n Read commands but do not execute them; this may be used to check a script for syntax errors. This option is ignored by interactive shells. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -o option-name Set the option corresponding to option-name: % Bash Shell - Bash Builtin Commands - set -o option set [-o option] allexport - Same as -a. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] braceexpand - Same as -B. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] emacs - Use an emacs-style line editing interface. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] errexit - Same as -e. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] hashall - Same as -h. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] histexpand - Same as -H. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] history - Enable command history, as described in 9.1 Bash History Facilities. This option is on by default in interactive shells. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] ignoreeof - An interactive shell will not exit upon reading EOF. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] keyword - Same as -k. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] monitor - Same as -m. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] noclobber - Same as -C. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] noexec - Same as -n. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] noglob - Same as -f. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] nolog - Currently ignored. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] notify - Same as -b. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] nounset - Same as -u. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] onecmd - Same as -t. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] physical - Same as -P. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] posix - Change the behavior of Bash where the default operation differs from the POSIX 1003.2 standard to match the standard. This is intended to make Bash behave as a strict superset of that standard. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] privileged - Same as -p. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] verbose - Same as -v. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] vi - Use a vi-style line editing interface. % Bash Shell - Bash Builtin Commands - set -o option set [-o option] xtrace - Same as -x. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -p - Turn on privileged mode. In this mode, the $BASH_ENV and $ENV files are not processed, shell functions are not inherited from the environment, and the SHELLOPTS variable, if it appears in the environment, is ignored. If the shell is started with the effective user (group) id not equal to the real user (group) id, and the -p option is not supplied, these actions are taken and the effective user id is set to the real user id. If the % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -p option is supplied at startup, the effective user id is not reset. Turning this option off causes the effective user and group ids to be set to the real user and group ids. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -t Exit after reading and executing one command. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -u Treat unset variables as an error when performing parameter expansion. An error message will be written to the standard error, and a non-interactive shell will exit. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -v Print shell input lines as they are read. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -x Print a trace of simple commands and their arguments after they are expanded and before they are executed. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -B The shell will perform brace expansion. This option is on by default. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -C Prevent output redirection using `>', `>&', and `<>' from overwriting existing files. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -H Enable `!' style history substitution. This option is on by default for interactive shells. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -P If set, do not follow symbolic links when performing commands such as cd which change the current directory. The physical directory is used instead. By default, Bash follows the logical chain of directories when performing commands which change the current directory. For example, if `/usr/sys' is a symbolic link to `/usr/local/sys' then: $ cd /usr/sys; echo $PWD/usr/sys$ cd ..; pwd /usr If set -P is on, then: $ cd /usr/sys; echo $PWD/usr/local/sys$ cd ..; pwd /usr/local % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] -- If no arguments follow this option, then the positional parameters are unset. Otherwise, the positional parameters are set to the arguments, even if some of them begin with a `-'. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] - Signal the end of options, cause all remaining arguments to be assigned to the positional parameters. The `-x' and `-v' options are turned off. If there are no arguments, the positional parameters remain unchanged. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] Using `+' rather than `-' causes these options to be turned off. The options can also be used upon invocation of the shell. The current set of options may be found in $-. % Bash Shell - Bash Builtin Commands - set set set [--abefhkmnptuvxBCHP] [-o option] [argument ...] The remaining N arguments are positional parameters and are assigned, in order, to $1, $2, ... $N. The special parameter # is set to N. The return status is always zero unless an invalid option is supplied. % Bash Shell - Special Builtins break : . continue eval exec exit export readonly return setshift trap unset For historical reasons, the POSIX 1003.2 standard has classified several builtin commands as special. When Bash is executing in POSIX mode, the special builtins differ from other builtin commands in three respects: 1. Special builtins are found before shell functions during command lookup. 2. If a special builtin returns an error status, a non-interactive shell exits. 3. Assignment statements preceding the command stay in effect in the shell environment after the command completes. % Bash Shell - Special Builtins break : . continue eval exec exit export readonly return setshift trap unset When Bash is not executing in POSIX mode, these builtins behave no differently than the rest of the Bash builtin commands. The Bash POSIX mode is described in 6.11 Bash POSIX Mode. % Bash Shell - Special Builtins These are the POSIX special builtins: break : . continue eval exec exit export readonly return setshift trap unset % Bash Shell - Bourne Shell Variables CDPATH A colon-separated list of directories used as a search path for the cd builtin command. % Bash Shell - Bourne Shell Variables HOME The current user's home directory; the default for the cd builtin command. The value of this variable is also used by tilde expansion. % Bash Shell - Bourne Shell Variables IFS A list of characters that separate fields; used when the shell splits words as part of expansion. % Bash Shell - Bourne Shell Variables MAIL If this parameter is set to a filename and the MAILPATH variable is not set, Bash informs The user of the arrival of mail in the specified file. % Bash Shell - Bourne Shell Variables MAILPATH A colon-separated list of filenames which the shell periodically checks for new mail. Each list entry can specify the message that is printed when new mail arrives in the mail file by separating the file name from the message with a `?'. When used in the text of the message, $_ expands to the name of the current mail file. % Bash Shell - Bourne Shell Variables OPTARG The value of the last option argument processed by the getopts builtin. % Bash Shell - Bourne Shell Variables OPTIND The index of the last option argument processed by the getopts builtin. % Bash Shell - Bourne Shell Variables PATH A colon-separated list of directories in which the shell looks for commands. % Bash Shell - Bourne Shell Variables PS1 The primary prompt string. The default value is `\s-\v\$ '. Controlling the Prompt, for the complete list of escape sequences that are expanded before PS1 is displayed. % Bash Shell - Bourne Shell Variables PS2 The secondary prompt string. The default value is `> '. % Bash Shell - Bash Variables BASH The full pathname used to execute the current instance of Bash. % Bash Shell - Bash Variables BASH_ENV If this variable is set when Bash is invoked to execute a shell script, its value is expanded and used as the name of a startup file to read before executing the script. % Bash Shell - Bash Variables BASH_VERSION The version number of the current instance of Bash. % Bash Shell - Bash Variables BASH_VERSINFO A readonly array variable whose members hold version information for this instance of Bash. The values assigned to the array members are as follows: % Bash Shell - Bash Variables BASH_VERSINFO[0] The major version number (the release). % Bash Shell - Bash Variables BASH_VERSINFO[1] The minor version number (the version). % Bash Shell - Bash Variables BASH_VERSINFO[2] The patch level. % Bash Shell - Bash Variables BASH_VERSINFO[3] The build version. % Bash Shell - Bash Variables BASH_VERSINFO[4] The release status (e.g., beta1). % Bash Shell - Bash Variables BASH_VERSINFO[5] The value of MACHTYPE. % Bash Shell - Bash Variables COLUMNS Used by the select builtin command to determine the terminal width when printing selection lists. Automatically set upon receipt of a SIGWINCH. % Bash Shell - Bash Variables COMP_CWORD An index into ${COMP_WORDS} of the word containing the current cursor position. This variable is available only in shell functions invoked by the programmable completion facilities. % Bash Shell - Bash Variables COMP_LINE The current command line. This variable is available only in shell functions and external commands invoked by the programmable completion facilities. % Bash Shell - Bash Variables COMP_POINT The index of the current cursor position relative to the beginning of the current command. If the current cursor position is at the end of the current command, the value of this variable is equal to ${#COMP_LINE}. This variable is available only in shell functions and external commands invoked by the programmable completion facilities. % Bash Shell - Bash Variables COMP_WORDS An array variable consisting of the individual words in the current command line. This variable is available only in shell functions invoked by the programmable completion facilities. % Bash Shell - Bash Variables COMPREPLY An array variable from which Bash reads the possible completions generated by a shell function invoked by the programmable completion facility. % Bash Shell - Bash Variables DIRSTACK An array variable containing the current contents of the directory stack. Directories appear in the stack in the order they are displayed by the dirs builtin. Assigning to members of this array variable may be used to modify directories already in the stack, but the pushd and popd builtins must be used to add and remove directories. Assignment to this variable will not change the current directory. If DIRSTACK is unset, it loses its special properties, even if it is subsequently reset. % Bash Shell - Bash Variables EUID The numeric effective user id of the current user. This variable is readonly. % Bash Shell - Bash Variables FCEDIT The editor used as a default by the `-e' option to the fc builtin command. % Bash Shell - Bash Variables FIGNORE A colon-separated list of suffixes to ignore when performing filename completion. A file name whose suffix matches one of the entries in FIGNORE is excluded from the list of matched file names. A sample value is `.o:~' % Bash Shell - Bash Variables FUNCNAME The name of any currently-executing shell function. This variable exists only when a shell function is executing. Assignments to FUNCNAME have no effect and return an error status. If FUNCNAME is unset, it loses its special properties, even if it is subsequently reset. % Bash Shell - Bash Variables GLOBIGNORE A colon-separated list of patterns defining the set of filenames to be ignored by filename expansion. If a filename matched by a filename expansion pattern also matches one of the patterns in GLOBIGNORE, it is removed from the list of matches. % Bash Shell - Bash Variables GROUPS An array variable containing the list of groups of which the current user is a member. Assignments to GROUPS have no effect and return an error status. If GROUPS is unset, it loses its special properties, even if it is subsequently reset. histchars Up to three characters which control history expansion, quick substitution, and tokenization. The first character is the history expansion character, that is, the character which signifies the start of a history expansion, normally `!'. The second character is the character which signifies `quick substitution' when seen as the first character on a line, normally `^'. The optional third character is the character which indicates that the remainder of the line is a comment when found as the first character of a word, usually `#'. The history comment character causes history substitution to be skipped for the remaining words on the line. It does not necessarily cause the shell parser to treat the rest of the line as a comment. % Bash Shell - Bash Variables HISTCMD The history number, or index in the history list, of the current command. If HISTCMD is unset, it loses its special properties, even if it is subsequently reset. % Bash Shell - Bash Variables HISTCONTROL A value of `ignorespace' means to not enter lines which begin with a space or tab into the history list. A value of `ignoredups' means to not enter lines which match the last entered line. A value of `ignoreboth' combines the two options. Unset, or set to any other value than those above, means to save all lines on the history list. The second and subsequent lines of a multi-line compound command are not tested, and are added to the history regardless of the value of HISTCONTROL. % Bash Shell - Bash Variables HISTFILE The name of the file to which the command history is saved. The default value is `~/.bash_history'. % Bash Shell - Bash Variables HISTFILESIZE The maximum number of lines contained in the history file. When this variable is assigned a value, the history file is truncated, if necessary, to contain no more than that number of lines. The history file is also truncated to this size after writing it when an interactive shell exits. The default value is 500. % Bash Shell - Bash Variables HISTIGNORE A colon-separated list of patterns used to decide which command lines should be saved on the history list. Each pattern is anchored at the beginning of the line and must match the complete line (no implicit `*' is appended). Each pattern is tested against the line after the checks specified by HISTCONTROL are applied. In addition to the normal shell pattern matching characters, `&' matches the previous history line. `&' may be escaped using a backslash; the backslash is removed before attempting a match. The second and subsequent lines of a multi-line compound command are not tested, and are added to the history regardless of the value of HISTIGNORE. HISTIGNORE subsumes the function of HISTCONTROL. A pattern of `&' is identical to ignoredups, and a pattern of `[ ]*' is identical to ignorespace. Combining these two patterns, separating them with a colon, provides the functionality of ignoreboth. % Bash Shell - Bash Variables HISTSIZE The maximum number of commands to remember on the history list. The default value is 500. % Bash Shell - Bash Variables HOSTFILE Contains the name of a file in the same format as `/etc/hosts' that should be read when the shell needs to complete a hostname. The list of possible hostname completions may be changed while the shell is running; the next time hostname completion is attempted after the value is changed, Bash adds the contents of the new file to the existing list. If HOSTFILE is set, but has no value, Bash attempts to read `/etc/hosts' to obtain the list of possible hostname completions. When HOSTFILE is unset, the hostname list is cleared. % Bash Shell - Bash Variables HOSTNAME The name of the current host. % Bash Shell - Bash Variables HOSTTYPE A string describing the machine Bash is running on. % Bash Shell - Bash Variables IGNOREEOF Controls the action of the shell on receipt of an EOF character as the sole input. If set, the value denotes the number of consecutive EOF characters that can be read as the first character on an input line before the shell will exit. If the variable exists but does not have a numeric value (or has no value) then the default is 10. If the variable does not exist, then EOF signifies the end of input to the shell. This is only in effect for interactive shells. % Bash Shell - Bash Variables INPUTRC The name of the Readline initialization file, overriding the default of `~/.inputrc'. % Bash Shell - Bash Variables LANG Used to determine the locale category for any category not specifically selected with a variable starting with LC_. % Bash Shell - Bash Variables LC_ALL This variable overrides the value of LANG and any other LC_ variable specifying a locale category. % Bash Shell - Bash Variables LC_COLLATE This variable determines the collation order used when sorting the results of filename expansion, and determines the behavior of range expressions, equivalence classes, and collating sequences within filename expansion and pattern matching. % Bash Shell - Bash Variables LC_CTYPE This variable determines the interpretation of characters and the behavior of character classes within filename expansion and pattern matching. % Bash Shell - Bash Variables LC_MESSAGES This variable determines the locale used to translate double-quoted strings preceded by a `$'. % Bash Shell - Bash Variables LC_NUMERIC This variable determines the locale category used for number formatting. % Bash Shell - Bash Variables LINENO The line number in the script or shell function currently executing. % Bash Shell - Bash Variables LINES Used by the select builtin command to determine the column length for printing selection lists. Automatically set upon receipt of a SIGWINCH. % Bash Shell - Bash Variables MACHTYPE A string that fully describes the system type on which Bash is executing, in the standard GNU cpu-company-system format. % Bash Shell - Bash Variables MAILCHECK How often (in seconds) that the shell should check for mail in the files specified in the MAILPATH or MAIL variables. The default is 60 seconds. When it is time to check for mail, the shell does so before displaying the primary prompt. If this variable is unset, or set to a value that is not a number greater than or equal to zero, the shell disables mail checking. % Bash Shell - Bash Variables OLDPWD The previous working directory as set by the cd builtin. % Bash Shell - Bash Variables OPTERR If set to the value 1, Bash displays error messages generated by the getopts builtin command. % Bash Shell - Bash Variables OSTYPE A string describing the operating system Bash is running on. % Bash Shell - Bash Variables PIPESTATUS An array variable containing a list of exit status values from the processes in the most-recently-executed foreground pipeline (which may contain only a single command). % Bash Shell - Bash Variables POSIXLY_CORRECT If this variable is in the environment when bash starts, the shell enters POSIX mode before reading the startup files, as if the `-- posix' invocation option had been supplied. If it is set while the shell is running, bash enables POSIX mode, as if the command set -o posix had been executed. % Bash Shell - Bash Variables PPID The process ID of the shell's parent process. This variable is readonly. % Bash Shell - Bash Variables PROMPT_COMMAND If set, the value is interpreted as a command to execute before the printing of each primary prompt ($PS1). % Bash Shell - Bash Variables PS3 The value of this variable is used as the prompt for the select command. If this variable is not set, the select command prompts with `#? ' % Bash Shell - Bash Variables PS4 The value is the prompt printed before the command line is echoed when the `-x' option is set. The first character of PS4 is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is `+'. % Bash Shell - Bash Variables PWD The current working directory as set by the cd builtin. % Bash Shell - Bash Variables RANDOM Each time this parameter is referenced, a random integer between 0 and 32767 is generated. Assigning a value to this variable seeds the random number generator. % Bash Shell - Bash Variables REPLY The default variable for the read builtin. % Bash Shell - Bash Variables SECONDS This variable expands to the number of seconds since the shell was started. Assignment to this variable resets the count to the value assigned, and the expanded value becomes the value assigned plus the number of seconds since the assignment. % Bash Shell - Bash Variables SHELLOPTS A colon-separated list of enabled shell options. Each word in the list is a valid argument for the `-o' option to the set builtin command. The options appearing in SHELLOPTS are those reported as `on' by `set -o'. If this variable is in the environment when Bash starts up, each shell option in the list will be enabled before reading any startup files. This variable is readonly. % Bash Shell - Bash Variables SHLVL Incremented by one each time a new instance of Bash is started. This is intended to be a count of how deeply your Bash shells are nested. % Bash Shell - Bash Variables - TIMEFORMAT TIMEFORMAT The value of this parameter is used as a format string specifying how the timing information for pipelines prefixed with the time reserved word should be displayed. The `%' character introduces an escape sequence that is expanded to a time value or other information. The escape sequences and their meanings are as follows; the braces denote optional portions. % Bash Shell - Bash Variables - TIMEFORMAT TIMEFORMAT %% A literal `%'. % Bash Shell - Bash Variables - TIMEFORMAT %[p][l]R The elapsed time in seconds. % Bash Shell - Bash Variables - TIMEFORMAT %[p][l]U The number of CPU seconds spent in user mode. % Bash Shell - Bash Variables - TIMEFORMAT %[p][l]S The number of CPU seconds spent in system mode. % Bash Shell - Bash Variables - TIMEFORMAT %P The CPU percentage, computed as (%U + %S) / %R. The optional p is a digit specifying the precision, the number of fractional digits after a decimal point. A value of 0 causes no decimal point or fraction to be output. At most three places after the decimal point may be specified; values of p greater than 3 are changed to 3. If p is not specified, the value 3 is used. The optional l specifies a longer format, including minutes, of the form MMmSS.FFs. The value of p determines whether or not the fraction is included. % Bash Shell - Bash Variables - TIMEFORMAT If this variable is not set, Bash acts as if it had the value $'\nreal\t%3lR\nuser\t%3lU\nsys\t%3lS' If the value is null, no timing information is displayed. A trailing newline is added when the format string is displayed. % Bash Shell - Bash Variables TMOUT If set to a value greater than zero, TMOUT is treated as the default timeout for the read builtin. The select command terminates if input does not arrive after TMOUT seconds when input is coming from a terminal. In an interative shell, the value is interpreted as the number of seconds to wait for input after issuing the primary prompt when the shell is interactive. Bash terminates after that number of seconds if input does not arrive. % Bash Shell - Bash Variables UID The numeric real user id of the current user. This variable is readonly. % Bash Shell - Invoking Bash bash [long-opt] [-ir] [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] [argument ...] bash [long-opt] [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] -c string [argument ...] bash [long-opt] -s [-abefhkmnptuvxdBCDHP] [-o option] [-O shopt_option] [argument ...] In addition to the single-character shell command-line options, there are several multi-character options that you can use. These options must appear on the command line before the single-character options to be recognized. % Bash Shell - Invoking Bash --dump-po-strings A list of all double-quoted strings preceded by `$' is printed on the standard ouput in the GNU gettext PO (portable object) file format. Equivalent to `-D' except for the output format. % Bash Shell - Invoking Bash --dump-strings Equivalent to `-D'. % Bash Shell - Invoking Bash --help Display a usage message on standard output and exit sucessfully. % Bash Shell - Invoking Bash --init-file filename % Bash Shell - Invoking Bash --rcfile filename Execute commands from filename (instead of `~/.bashrc') in an interactive shell. % Bash Shell - Invoking Bash --login Equivalent to `-l'. % Bash Shell - Invoking Bash --noediting Do not use the GNU Readline library to read command lines when the shell is interactive. % Bash Shell - Invoking Bash --noprofile Don't load the system-wide startup file `/etc/profile' or any of the personal initialization files `~/.bash_profile', `~/.bash_login', or `~/.profile' when Bash is invoked as a login shell. % Bash Shell - Invoking Bash --norc Don't read the `~/.bashrc' initialization file in an interactive shell. This is on by default if the shell is invoked as sh. % Bash Shell - Invoking Bash --posix Change the behavior of Bash where the default operation differs from the POSIX 1003.2 standard to match the standard. This is intended to make Bash behave as a strict superset of that standard. % Bash Shell - Invoking Bash --restricted Make the shell a restricted shell. % Bash Shell - Invoking Bash --verbose Equivalent to `-v'. Print shell input lines as they're read. % Bash Shell - Invoking Bash --version Show version information for this instance of Bash on the standard output and exit successfully. % Bash Shell - Invoking Bash - options -c string Read and execute commands from string after processing the options, then exit. Any remaining arguments are assigned to the positional parameters, starting with $0. % Bash Shell - Invoking Bash - options -i Force the shell to run interactively. Interactive shells are described in 6.3 Interactive Shells. % Bash Shell - Invoking Bash - options -l Make this shell act as if it had been directly invoked by login. When the shell is interactive, this is equivalent to starting a login shell with `exec -l bash'. When the shell is not interactive, the login shell startup files will be executed. `exec bash -l' or `exec bash --login' will replace the current shell with a Bash login shell. % Bash Shell - Invoking Bash - options -r Make the shell a restricted shell. % Bash Shell - Invoking Bash - options -s If this option is present, or if no arguments remain after option processing, then commands are read from the standard input. This option allows the positional parameters to be set when invoking an interactive shell. % Bash Shell - Invoking Bash - options -D A list of all double-quoted strings preceded by `$' is printed on the standard ouput. These are the strings that are subject to language translation when the current locale is not C or POSIX. This implies the `- n' option; no commands will be executed. % Bash Shell - Invoking Bash - options [-+]O [shopt_option] shopt_option is one of the shell options accepted by the shopt builtin. If shopt_option is present, `-O' sets the value of that option; `+O' unsets it. If shopt_option is not supplied, the names and values of the shell options accepted by shopt are printed on the standard output. If the invocation option is `+O', the output is displayed in a format that may be reused as input. % Bash Shell - Invoking Bash -- A -- signals the end of options and disables further option processing. Any arguments after the -- are treated as filenames and arguments. % Bash Shell - Invoking Bash - options A login shell is one whose first character of argument zero is `-', or one invoked with the `- -login' option. % Bash Shell - Invoking Bash - options An interactive shell is one started without non-option arguments, unless `-s' is specified, without specifying the `-c' option, and whose input and output are both connected to terminals (as determined by isatty(3)), or one started with the `-i' option. % Bash Shell - Invoking Bash - options If arguments remain after option processing, and neither the `-c' nor the `-s' option has been supplied, the first argument is assumed to be the name of a file containing shell commands. When Bash is invoked in this fashion, $0 is set to the name of the file, and the positional parameters are set to the remaining arguments. Bash reads and executes commands from this file, then exits. Bash's exit status is the exit status of the last command executed in the script. If no commands are executed, the exit status is 0. % Bash Shell - Bash Startup Files When Bash is invoked as an interactive login shell, or as a non-interactive shell with the `-- login' option, it first reads and executes commands from the file `/etc/profile', if that file exists. After reading that file, it looks for `~/.bash_profile', `~/.bash_login', and `~/.profile', in that order, and reads and executes commands from the first one that exists and is readable. The `--noprofile' option may be used when the shell is started to inhibit this behavior. % Bash Shell - Bash Startup Files When a login shell exits, Bash reads and executes commands from the file `~/.bash_logout', if it exists. % Bash Shell - Bash Startup Files When an interactive shell that is not a login shell is started, Bash reads and executes commands from `~/.bashrc', if that file exists. This may be inhibited by using the `--norc' option. % Bash Shell - Bash Startup Files The `--rcfile file' option will force Bash to read and execute commands from file instead of `~/.bashrc'. So, typically, your `~/.bash_profile' contains the line if [ -f ~/.bashrc ]; then . ~/.bashrc; fi after (or before) any login-specific initializations. % Bash Shell - Bash Startup Files When Bash is started non-interactively, to run a shell script, for example, it looks for the variable BASH_ENV in the environment, expands its value if it appears there, and uses the expanded value as the name of a file to read and execute. Bash behaves as if the following command were executed: if [ -n "$BASH_ENV" ]; then . "$BASH_ENV"; fi but the value of the PATH variable is not used to search for the file name. As noted above, if a non-interactive shell is invoked with the `--login' option, Bash attempts to read and execute commands from the login shell startup files. % Bash Shell - Bash Startup Files If Bash is invoked with the name sh, it tries to mimic the startup behavior of historical versions of sh as closely as possible, while conforming to the POSIX standard as well. % Bash Shell - Bash Startup Files When invoked as an interactive login shell, or as a non-interactive shell with the `--login' option, it first attempts to read and execute commands from `/etc/profile' and `~/.profile', in that order. The `--noprofile' option may be used to inhibit this behavior. When invoked as an interactive shell with the name sh, Bash looks for the variable % Bash Shell - Bash Startup Files ENV, expands its value if it is defined, and uses the expanded value as the name of a file to read and execute. Since a shell invoked as sh does not attempt to read and execute commands from any other startup files, the `--rcfile' option has no effect. A non-interactive shell invoked with the name sh does not attempt to read any other startup files. % Bash Shell - Bash Startup Files When invoked as sh, Bash enters POSIX mode after the startup files are read. % Bash Shell - Bash Startup Files When Bash is started in POSIX mode, as with the `--posix' command line option, it follows the POSIX standard for startup files. In this mode, interactive shells expand the ENV variable and commands are read and executed from the file whose name is the expanded value. No other startup files are read. % Bash Shell - Bash Startup Files Bash attempts to determine when it is being run by the remote shell daemon, usually rshd. If Bash determines it is being run by rshd, it reads and executes commands from `~/.bashrc', if that file exists and is readable. It will not do this if invoked as sh. The `--norc' option may be used to inhibit this behavior, and the `--rcfile' option may be used to force another file to be read, but rshd does not generally invoke the shell with those options or allow them to be specified. % Bash Shell - Bash Startup Files If Bash is started with the effective user (group) id not equal to the real user (group) id, and the -p option is not supplied, no startup files are read, shell functions are not inherited from the environment, the SHELLOPTS variable, if it appears in the environment, is ignored, and the effective user id is set to the real user id. If the -p option is supplied at invocation, the startup behavior is the same, but the effective user id is not reset. % Bash Shell - What is an Interactive Shell? An interactive shell is one started without non-option arguments, unless `-s' is specified, without specifiying the `-c' option, and whose input and output are both connected to terminals (as determined by isatty(3)), or one started with the `-i' option. % Bash Shell - What is an Interactive Shell? An interactive shell generally reads from and writes to a user's terminal. % Bash Shell - What is an Interactive Shell? The `-s' invocation option may be used to set the positional parameters when an interactive shell is started. % Bash Shell - Is this Shell Interactive? To determine within a startup script whether or not Bash is running interactively, test the value of the `-' special parameter. It contains i when the shell is interactive. For example: case "$-" in* i*) echo This shell is interactive ;; *) echo This shell is not interactive ;; esac % Bash Shell - Is this Shell Interactive? Startup scripts may examine the variable PS1; it is unset in non-interactive shells, and set in interactive shells. Thus: if [ -z "$PS1" ]; then echo This shell is not interactive else echo This shell is interactive fi % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 1. Startup files are read and executed as described in 6.2 Bash Startup Files. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 2. Job Control is enabled by default. When job control is in effect, Bash ignores the keyboard-generated job control signals SIGTTIN, SIGTTOU, and SIGTSTP. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 3. Bash expands and displays PS1 before reading the first line of a command, and expands and displays PS2 before reading the second and subsequent lines of a multi-line command. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 4. Bash executes the value of the PROMPT_COMMAND variable as a command before printing the primary prompt, $PS1. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 5. Readline is used to read commands from the user's terminal. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 6. Bash inspects the value of the ignoreeof option to set -o instead of exiting immediately when it receives an EOF on its standard input when reading a command. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 7. Command history and history expansion are enabled by default. Bash will save the command history to the file named by $HISTFILE when an interactive shell exits. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 8. Alias expansion is performed by default. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 9. In the absence of any traps, Bash ignores SIGTERM. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. 10. In the absence of any traps, SIGINT is caught and handled . SIGINT will interrupt some shell builtins. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 11. An interactive login shell sends a SIGHUP to all jobs on exit if the hupoxexit shell option has been enabled. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 12. The `-n' invocation option is ignored, and `set -n' has no effect. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 13. Bash will check for mail periodically, depending on the values of the MAIL, MAILPATH, and MAILCHECK shell variables. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 14. Expansion errors due to references to unbound shell variables after `set -u' has been enabled will not cause the shell to exit. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 15. The shell will not exit on expansion errors caused by var being unset or null in ${var:?word} expansions. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 16. Redirection errors encountered by shell builtins will not cause the shell to exit. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 17. When running in POSIX mode, a special builtin returning an error status will not cause the shell to exit. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 18. A failed exec will not cause the shell to exit. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 19. Parser syntax errors will not cause the shell to exit. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 20. Simple spelling correction for directory arguments to the cd builtin is enabled by default. % Bash Shell - Interactive Shell Behavior When the shell is running interactively, it changes its behavior in several ways. Change 21. The shell will check the value of the TMOUT variable and exit if a command is not read within the specified number of seconds after printing $PS1. % Bash Shell - Bash Conditional Expressions Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions Expressions may be unary or binary. Unary expressions are often used to examine the status of a file. There are string operators and numeric comparison operators as well. If the file argument to one of the primaries is of the form `/dev/fd/N', then file descriptor N is checked. If the file argument to one of the primaries is one of `/dev/stdin', `/dev/stdout', or `/dev/stderr', file descriptor 0, 1, or 2, respectively, is checked. % Bash Shell - Bash Conditional Expressions -a file True if file exists. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -b file True if file exists and is a block special file. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -c file True if file exists and is a character special file. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -d file True if file exists and is a directory. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -e file True if file exists. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -f file True if file exists and is a regular file. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -g file True if file exists and its set-group-id bit is set. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -h file True if file exists and is a symbolic link. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -k file True if file exists and its "sticky" bit is set. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -p file True if file exists and is a named pipe (FIFO). Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -r file True if file exists and is readable. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -s file True if file exists and has a size greater than zero. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -t fd True if file descriptor fd is open and refers to a terminal. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -u file True if file exists and its set-user-id bit is set. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -w file True if file exists and is writable. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -x file True if file exists and is executable. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -O file True if file exists and is owned by the effective user id. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -G file True if file exists and is owned by the effective group id. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -L file True if file exists and is a symbolic link. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -S file True if file exists and is a socket. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -N file True if file exists and has been modified since it was last read. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions file1 -nt file2 True if file1 is newer (according to modification date) than file2, or if file1 exists and file2 does not. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions file1 -ot file2 True if file1 is older than file2, or if file2 exists and file1 does not. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions file1 -ef file2 True if file1 and file2 refer to the same device and inode numbers. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -o optname True if shell option optname is enabled. The list of options appears in the description of the `-o' option to the set builtin. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -z string True if the length of string is zero. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions -n string string True if the length of string is non-zero. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions string1 == string2 True if the strings are equal. `=' may be used in place of `==' for strict POSIX compliance. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions string1 != string2 True if the strings are not equal. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions string1 < string2 True if string1 sorts before string2 lexicographically in the current locale. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions string1 > string2 True if string1 sorts after string2 lexicographically in the current locale. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Bash Conditional Expressions arg1 OP arg2 OP is one of `-eq', `-ne', `-lt', `-le', `-gt', or `-ge'. These arithmetic binary operators return true if arg1 is equal to, not equal to, less than, less than or equal to, greater than, or greater than or equal to arg2, respectively. Arg1 and arg2 may be positive or negative integers. Conditional expressions are used by the [[ compound command and the test and [ builtin commands. % Bash Shell - Shell Arithmetic The shell allows arithmetic expressions to be evaluated, as one of the shell expansions or by the let builtin. % Bash Shell - Shell Arithmetic Evaluation is done in fixed-width integers with no check for overflow, though division by 0 is trapped and flagged as an error. The operators and their precedence and associativity are the same as in the C language. % Bash Shell - Shell Arithmetic - Precedence Level: 1 id++ id-- variable post-increment and post-decrement % Bash Shell - Shell Arithmetic - Precedence Level: 2 ++id --id variable pre-increment and pre-decrement % Bash Shell - Shell Arithmetic - Precedence Level: 3 - + unary minus and plus % Bash Shell - Shell Arithmetic - Precedence Level: 4 ! ~ logical and bitwise negation % Bash Shell - Shell Arithmetic - Precedence Level: 5 ** exponentiation % Bash Shell - Shell Arithmetic - Precedence Level: 6 * / % multiplication, division, remainder % Bash Shell - Shell Arithmetic - Precedence Level: 7 + - addition, subtraction % Bash Shell - Shell Arithmetic - Precedence Level: 8 << >> left and right bitwise shifts % Bash Shell - Shell Arithmetic - Precedence Level: 9 <= >= < > comparison % Bash Shell - Shell Arithmetic - Precedence Level: 10 == != equality and inequality % Bash Shell - Shell Arithmetic - Precedence Level: 11 & bitwise AND % Bash Shell - Shell Arithmetic - Precedence Level: 12 ^ bitwise exclusive OR % Bash Shell - Shell Arithmetic - Precedence Level: 13 | bitwise OR % Bash Shell - Shell Arithmetic - Precedence Level: 14 && logical AND % Bash Shell - Shell Arithmetic - Precedence Level: 15 || logical OR % Bash Shell - Shell Arithmetic - Precedence Level: 16 expr ? expr : expr conditional evaluation % Bash Shell - Shell Arithmetic - Precedence Level: 17 = *= /= %= += -= <<= >>= &= ^= |= assignment % Bash Shell - Shell Arithmetic - Precedence Level: 18 expr1 , expr2 comma % Bash Shell - Shell Arithmetic Shell variables are allowed as operands; parameter expansion is performed before the expression is evaluated. Within an expression, shell variables may also be referenced by name without using the parameter expansion syntax. The value of a variable is evaluated as an arithmetic expression when it is referenced. A shell variable need not have its integer attribute turned on to be used in an expression. % Bash Shell - Shell Arithmetic Constants with a leading 0 are interpreted as octal numbers. A leading `0x' or `0X' denotes hexadecimal. Otherwise, numbers take the form [base#]n, where base is a decimal number between 2 and 64 representing the arithmetic base, and n is a number in that base. If base# is omitted, then base 10 is used. The digits greater than 9 are represented by the lowercase letters, the uppercase letters, `@', and `_', in that order. If base is less than or equal to 36, lowercase and uppercase letters may be used interchangably to represent numbers between 10 and 35. % Bash Shell - Shell Arithmetic Operators are evaluated in order of precedence. Sub-expressions in parentheses are evaluated first and may override the precedence rules. % Bash Shell - Aliases Aliases allow a string to be substituted for a word when it is used as the first word of a simple command. The shell maintains a list of aliases that may be set and unset with the alias and unalias builtin commands. % Bash Shell - Aliases The first word of each simple command, if unquoted, is checked to see if it has an alias. If so, that word is replaced by the text of the alias. The alias name and the replacement text may contain any valid shell input, including shell metacharacters, with the exception that the alias name may not contain `='. The first word of the replacement text is tested for aliases, but a word that is identical to an alias being expanded is not expanded a second time. This means that one may alias ls to "ls -F", for instance, and Bash does not try to recursively expand the replacement text. If the last character of the alias value is a space or tab character, then the next command word following the alias is also checked for alias expansion. % Bash Shell - Aliases Aliases are created and listed with the alias command, and removed with the unalias command. % Bash Shell - Aliases There is no mechanism for using arguments in the replacement text, as in csh. If arguments are needed, a shell function should be used. % Bash Shell - Aliases Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt. % Bash Shell - Aliases The rules concerning the definition and use of aliases are somewhat confusing. Bash always reads at least one complete line of input before executing any of the commands on that line. % Bash Shell - Aliases Aliases are expanded when a command is read, not when it is executed. Therefore, an alias definition appearing on the same line as another command does not take effect until the next line of input is read. The commands following the alias definition on that line are not affected by the new alias. This behavior is also an issue when functions are executed. Aliases are expanded when a function definition is read, not when the function is executed, because a function definition is itself a compound command. As a consequence, aliases defined in a function are not available until after that function is executed. To be safe, always put alias definitions on a separate line, and do not use alias in compound commands. % Bash Shell - Aliases For almost every purpose, shell functions are preferred over aliases. % Bash Shell - Arrays Bash provides one-dimensional array variables. Any variable may be used as an array; the declare builtin will explicitly declare an array. There is no maximum limit on the size of an array, nor any requirement that members be indexed or assigned contiguously. Arrays are zero- based. % Bash Shell - Arrays An array is created automatically if any variable is assigned to using the syntax name[subscript]=value The subscript is treated as an arithmetic expression that must evaluate to a number greater than or equal to zero. % Bash Shell - Arrays To explicitly declare an array, use declare -a name The syntax declare -a name[subscript] is also accepted; the subscript is ignored. Attributes may be specified for an array variable using the declare and readonly builtins. Each attribute applies to all members of an array. % Bash Shell - Arrays Arrays are assigned to using compound assignments of the form name=(value1 ... valuen) where each value is of the form [[subscript]=]string. If the optional subscript is supplied, that index is assigned to; otherwise the index of the element assigned is the last index assigned to by the statement plus one. Indexing starts at zero. This syntax is also accepted by the declare builtin. Individual array elements may be assigned to using the name[subscript]=value syntax introduced above. % Bash Shell - Arrays Any element of an array may be referenced using ${name[subscript]}. The braces are required to avoid conflicts with the shell's filename expansion operators. If the subscript is `@' or `*', the word expands to all members of the array name. These subscripts differ only when the word appears within double quotes. If the word is double-quoted, ${name[*]} expands to a single word with the value of each array member separated by the first character of the IFS variable, and ${name[@]} expands each element of name to a separate word. When there are no array members, ${name[@]} expands to nothing. This is analogous to the expansion of the special parameters `@' and `*'. ${#name[subscript]} expands to the length of ${name[subscript]}. If subscript is `@' or `*', the expansion is the number of elements in the array. Referencing an array variable without a subscript is equivalent to referencing element zero. % Bash Shell - Arrays The unset builtin is used to destroy arrays. unset name[subscript] destroys the array element at index subscript. unset name, where name is an array, removes the entire array. A subscript of `*' or `@' also removes the entire array. % Bash Shell - Arrays The declare, local, and readonly builtins each accept a `-a' option to specify an array. % Bash Shell - Arrays The read builtin accepts a `-a' option to assign a list of words read from the standard input to an array, and can read values from the standard input into individual array elements. The set and declare builtins display array values in a way that allows them to be reused as input. % Bash Shell - Directory Stack Builtins The directory stack is a list of recently-visited directories. The pushd builtin adds directories to the stack as it changes the current directory, and the popd builtin removes specified directories from the stack and changes the current directory to the directory removed. The dirs builtin displays the contents of the directory stack. The contents of the directory stack are also visible as the value of the DIRSTACK shell variable. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] Display the list of currently remembered directories. Directories are added to the list with the pushd command; the popd command removes directories from the list. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] +N Displays the Nth directory (counting from the left of the list printed by dirs when invoked without options), starting with zero. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] -N Displays the Nth directory (counting from the right of the list printed by dirs when invoked without options), starting with zero. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] -c Clears the directory stack by deleting all of the elements. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] -l Produces a longer listing; the default listing format uses a tilde to denote the home directory. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] -p Causes dirs to print the directory stack with one entry per line. % Bash Shell - Directory Stack Builtins dirs dirs [+N | -N] [-clpv] -v Causes dirs to print the directory stack with one entry per line, prefixing each entry with its index in the stack. % Bash Shell - Directory Stack Builtins popd popd [+N | -N] [-n] Remove the top entry from the directory stack, and cd to the new top directory. When no arguments are given, popd removes the top directory from the stack and performs a cd to the new top directory. The elements are numbered from 0 starting at the first directory listed with dirs; i.e., popd is equivalent to popd +0. % Bash Shell - Directory Stack Builtins popd popd [+N | -N] [-n] +N Removes the Nth directory (counting from the left of the list printed by dirs), starting with zero. % Bash Shell - Directory Stack Builtins popd popd [+N | -N] [-n] -N Removes the Nth directory (counting from the right of the list printed by dirs), starting with zero. % Bash Shell - Directory Stack Builtins popd popd [+N | -N] [-n] -n Suppresses the normal change of directory when removing directories from the stack, so that only the stack is manipulated. pushd % Bash Shell - Directory Stack Builtins pushd [dir | +N | -N] [-n] Save the current directory on the top of the directory stack and then cd to dir. With no arguments, pushd exchanges the top two directories. % Bash Shell - Directory Stack Builtins pushd [dir | +N | -N] [-n] +N Brings the Nth directory (counting from the left of the list printed by dirs, starting with zero) to the top of the list by rotating the stack. % Bash Shell - Directory Stack Builtins pushd [dir | +N | -N] [-n] -N Brings the Nth directory (counting from the right of the list printed by dirs, starting with zero) to the top of the list by rotating the stack. % Bash Shell - Directory Stack Builtins pushd [dir | +N | -N] [-n] -n Suppresses the normal change of directory when adding directories to the stack, so that only the stack is manipulated. % Bash Shell - Directory Stack Builtins dir Makes the current working directory be the top of the stack, and then executes the equivalent of `cd dir'. cds to dir. % Bash Shell - Controlling the Prompt The value of the variable PROMPT_COMMAND is examined just before Bash prints each primary prompt. If PROMPT_COMMAND is set and has a non-null value, then the value is executed just as if it had been typed on the command line. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \a A bell character. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \d The date, in "Weekday Month Date" format (e.g., "Tue May 26"). % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \D{format} The format is passed to strftime(3) and the result is inserted into the prompt string; an empty format results in a locale-specific time representation. The braces are required. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \e An escape character. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \h The hostname, up to the first `.'. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \H The hostname. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \j The number of jobs currently managed by the shell. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \l The basename of the shell's terminal device name. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \n A newline. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \r A carriage return. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \s The name of the shell, the basename of $0 (the portion following the final slash). % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \t The time, in 24-hour HH:MM:SS format. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \T The time, in 12-hour HH:MM:SS format. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \@ The time, in 12-hour am/pm format. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \A The time, in 24-hour HH:MM format. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \u The username of the current user. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \v The version of Bash (e.g., 2.00) % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \V The release of Bash, version + patchlevel (e.g., 2.00.0) % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \w The current working directory. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \W The basename of $PWD. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \! The history number of this command. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \# The command number of this command. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \$ If the effective uid is 0, #, otherwise $. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \nnn The character whose ASCII code is the octal value nnn. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \\ A backslash. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \[ Begin a sequence of non-printing characters. This could be used to embed a terminal control sequence into the prompt. % Bash Shell - Controlling the Prompt - Special Characters Special characters which can appear in the prompt variables: \] End a sequence of non-printing characters. % Bash Shell - Controlling the Prompt The command number and the history number are usually different: the history number of a command is its position in the history list, which may include commands restored from the history file, while the command number is the position in the sequence of commands executed during the current shell session. % Bash Shell - Controlling the Prompt After the prompt string is decoded, it is expanded via parameter expansion, command substitution, arithmetic expansion, and quote removal, subject to the value of the promptvars shell option. % Bash Shell - The Restricted Shell If Bash is started with the name rbash, or the `--restricted' or `-r' option is supplied at invocation, the shell becomes restricted. A restricted shell is used to set up an environment more controlled than the standard shell. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Changing directories with the cd builtin. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Setting or unsetting the values of the SHELL, PATH, ENV, or BASH_ENV variables. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Specifying command names containing slashes. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Specifying a filename containing a slash as an argument to the . builtin command. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Specifying a filename containing a slash as an argument to the `-p' option to the hash builtin command. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Importing function definitions from the shell environment at startup. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Parsing the value of SHELLOPTS from the shell environment at startup. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Redirecting output using the `>', `>|', `<>', `>&', `&>', and `>>' redirection operators. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Using the exec builtin to replace the shell with another command. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Adding or deleting builtin commands with the `-f' and `-d' options to the enable builtin. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Using the enable builtin command to enable disabled shell builtins. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Specifying the `-p' option to the command builtin. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell Disallowed or not performed in a restricted shell: * Turning off restricted mode with `set +r' or `set +o restricted'. These restrictions are enforced after any startup files are read. % Bash Shell - The Restricted Shell When a command that is found to be a shell script is executed, rbash turns off any restrictions in the shell spawned to execute the script. % Bash Shell - Bash POSIX Mode Starting Bash with the `--posix' command-line option or executing `set -o posix' while Bash is running will cause Bash to conform more closely to the POSIX 1003.2 standard by changing the behavior to match that specified by POSIX in areas where the Bash default differs. % Bash Shell - Bash POSIX Mode When invoked as sh, Bash enters POSIX mode after reading the startup files. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: When a command in the hash table no longer exists, Bash will re-search $PATH to find the new location. This is also available with `shopt -s checkhash'. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The message printed by the job control code and builtins when a job exits with a non- zero status is `Done(status)'. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The message printed by the job control code and builtins when a job is stopped is `Stopped(signame)', where signame is, for example, SIGTSTP. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Reserved words may not be aliased. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The POSIX 1003.2 PS1 and PS2 expansions of `!' to the history number and `!!' to `!' are enabled, and parameter expansion is performed on the values of PS1 and PS2 regardless of the setting of the promptvars option. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Interactive comments are enabled by default. (Bash has them on by default anyway.) % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The POSIX 1003.2 startup files are executed ($ENV) rather than the normal Bash files. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Tilde expansion is only performed on assignments preceding a command name, rather than on all assignment statements on the line. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The default history file is `~/.sh_history' (this is the default value of $HISTFILE). % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The output of `kill -l' prints all the signal names on a single line, separated by spaces. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Non-interactive shells exit if filename in . filename is not found. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Non-interactive shells exit if a syntax error in an arithmetic expansion results in an invalid expression. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Redirection operators do not perform filename expansion on the word in the redirection unless the shell is interactive. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Redirection operators do not perform word splitting on the word in the redirection. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Function names must be valid shell names. That is, they may not contain characters other than letters, digits, and underscores, and may not start with a digit. Declaring a function with an invalid name causes a fatal syntax error in non-interactive shells. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: POSIX 1003.2 `special' builtins are found before shell functions during command lookup. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: If a POSIX 1003.2 special builtin returns an error status, a non-interactive shell exits. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The fatal errors are those listed in the POSIX.2 standard, and include things like passing incorrect options, redirection errors, variable assignment errors for assignments preceding the command name, and so on. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: If the cd builtin finds a directory to change to using $CDPATH, the value it assigns to the PWD variable does not contain any symbolic links, as if `cd -P' had been executed. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: If CDPATH is set, the cd builtin will not implicitly append the current directory to it. This means that cd will fail if no valid directory name can be constructed from any of the entries in $CDPATH, even if the a directory with the same name as the name given as an argument to cd exists in the current directory. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: A non-interactive shell exits with an error status if a variable assignment error occurs when no command name follows the assignment statements. A variable assignment error occurs, for example, when trying to assign a value to a readonly variable. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: A non-interactive shell exits with an error status if the iteration variable in a for statement or the selection variable in a select statement is a readonly variable. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Process substitution is not available. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Assignment statements preceding POSIX 1003.2 special builtins persist in the shell environment after the builtin completes. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Assignment statements preceding shell function calls persist in the shell environment after the function returns, as if a POSIX special builtin command had been executed. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The export and readonly builtin commands display their output in the format required by POSIX 1003.2. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The trap builtin displays signal names without the leading SIG. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: The . and source builtins do not search the current directory for the filename argument if it is not found by searching PATH. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Subshells spawned to execute command substitutions inherit the value of the `-e' option from the parent shell. When not in POSIX mode, Bash clears the `-e' option in such subshells. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: Alias expansion is always enabled, even in non-interactive shells. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: When the set builtin is invoked without options, it does not display shell function names and definitions. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: When the set builtin is invoked without options, it displays variable values without quotes, unless they contain shell metacharacters, even if the result contains nonprinting characters. % Bash Shell - Bash POSIX Mode Changed when 'POSIX mode' is in effect: When the cd builtin is invoked in logical mode, and the pathname constructed from $PWD and the directory name supplied as an argument does not refer to an existing directory, cd will fail instead of falling back to physical mode. % Bash Shell - Bash POSIX Mode POSIX 1003.2 behavior not implemented by bash: Assignment statements affect the execution environment of all builtins, not just special ones. % Bash Shell - Bash POSIX Mode POSIX 1003.2 behavior not implemented by bash: When a subshell is created to execute a shell script with execute permission, but without a leading `#!', Bash sets $0 to the full pathname of the script as found by searching $PATH, rather than the command as typed by the user. % Bash Shell - Bash POSIX Mode POSIX 1003.2 behavior not implemented by bash: When using `.' to source a shell script found in $PATH, bash checks execute permission bits rather than read permission bits, just as if it were searching for a command. % Bash Shell - Job Control Basics Job control refers to the ability to selectively stop (suspend) the execution of processes and continue (resume) their execution at a later point. A user typically employs this facility via an interactive interface supplied jointly by the system's terminal driver and Bash. % Bash Shell - Job Control Basics The shell associates a job with each pipeline. It keeps a table of currently executing jobs, which may be listed with the jobs command. When Bash starts a job asynchronously, it prints a line that looks like: [1] 25647 indicating that this job is job number 1 and that the process ID of the last process in the pipeline associated with this job is 25647. All of the processes in a single pipeline are members of the same job. Bash uses the job abstraction as the basis for job control. % Bash Shell - Job Control Basics To facilitate the implementation of the user interface to job control, the operating system maintains the notion of a current terminal process group ID. Members of this process group (processes whose process group ID is equal to the current terminal process group ID) receive keyboard-generated signals such as SIGINT. These processes are said to be in the foreground. % Bash Shell - Job Control Basics Background processes are those whose process group ID differs from the terminal's; such processes are immune to keyboard-generated signals. Only foreground processes are allowed to read from or write to the terminal. Background processes which attempt to read from (write to) the terminal are sent a SIGTTIN (SIGTTOU) signal by the terminal driver, which, unless caught, suspends the process. % Bash Shell - Job Control Basics If the operating system on which Bash is running supports job control, Bash contains facilities to use it. Typing the suspend character (typically `^Z', Control-Z) while a process is running causes that process to be stopped and returns control to Bash. Typing the delayed suspend character (typically `^Y', Control-Y) causes the process to be stopped when it attempts to read input from the terminal, and control to be returned to Bash. The user then manipulates the state of this job, using the bg command to continue it in the background, the fg command to continue it in the foreground, or the kill command to kill it. A `^Z' takes effect immediately, and has the additional side effect of causing pending output and typeahead to be discarded. % Bash Shell - Job Control Basics There are a number of ways to refer to a job in the shell. The character `%' introduces a job name. % Bash Shell - Job Control Basics Job number n may be referred to as `%n'. The symbols `%%' and `%+' refer to the shell's notion of the current job, which is the last job stopped while it was in the foreground or started in the background. The previous job may be referenced using `%-'. In output pertaining to jobs (e.g., the output of the jobs command), the current job is always flagged with a `+', and the previous job with a `-'. % Bash Shell - Job Control Basics A job may also be referred to using a prefix of the name used to start it, or using a substring that appears in its command line. For example, `%ce' refers to a stopped ce job. Using `%?ce', on the other hand, refers to any job containing the string `ce' in its command line. If the prefix or substring matches more than one job, Bash reports an error. % Bash Shell - Job Control Basics Simply naming a job can be used to bring it into the foreground: `%1' is a synonym for `fg %1', bringing job 1 from the background into the foreground. Similarly, `%1 &' resumes job 1 in the background, equivalent to `bg %1' % Bash Shell - Job Control Basics The shell learns immediately whenever a job changes state. Normally, Bash waits until it is about to print a prompt before reporting changes in a job's status so as to not interrupt any other output. If the `-b' option to the set builtin is enabled, Bash reports such changes immediately. Any trap on SIGCHLD is executed for each child process that exits. % Bash Shell - Job Control Basics If an attempt to exit Bash is while jobs are stopped, the shell prints a message warning that there are stopped jobs. The jobs command may then be used to inspect their status. If a second attempt to exit is made without an intervening command, Bash does not print another warning, and the stopped jobs are terminated. % Bash Shell - Job Control Builtins bg bg [jobspec] Resume the suspended job jobspec in the background, as if it had been started with `&'. If jobspec is not supplied, the current job is used. The return status is zero unless it is run when job control is not enabled, or, when run with job control enabled, if jobspec was not found or jobspec specifies a job that was started without job control. % Bash Shell - Job Control Builtins fg fg [jobspec] Resume the job jobspec in the foreground and make it the current job. If jobspec is not supplied, the current job is used. The return status is that of the command placed into the foreground, or non-zero if run when job control is disabled or, when run with job control enabled, jobspec does not specify a valid job or jobspec specifies a job that was started without job control. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] -l List process IDs in addition to the normal information. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] -n Display information only about jobs that have changed status since the user was last notified of their status. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] -p List only the process ID of the job's process group leader. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] -r Restrict output to running jobs. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] -s Restrict output to stopped jobs. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] If jobspec is given, output is restricted to information about that job. If jobspec is not supplied, the status of all jobs is listed. % Bash Shell - Job Control Builtins - jobs jobs jobs [-lnprs] [jobspec]jobs -x command [arguments] If the `-x' option is supplied, jobs replaces any jobspec found in command or arguments with the corresponding process group ID, and executes command, passing it arguments, returning its exit status. % Bash Shell - Job Control Builtins - kill kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid kill -l [exit_status] Send a signal specified by sigspec or signum to the process named by job specification jobspec or process ID pid. sigspec is either a signal name such as SIGINT (with or without the SIG prefix) or a signal number; signum is a signal number. If sigspec and signum are not present, SIGTERM is used. The `-l' option lists the signal names. If any arguments are supplied when `-l' is given, the names of the signals corresponding to the arguments are listed, and the return status is zero. exit_status is a number specifying a signal number or the exit status of a process terminated by a signal. % Bash Shell - Job Control Builtins - kill kill [-s sigspec] [-n signum] [-sigspec] jobspec or pid kill -l [exit_status] The return status is zero if at least one signal was successfully sent, or non-zero if an error occurs or an invalid option is encountered. wait % Bash Shell - Job Control Builtins wait [jobspec or pid] Wait until the child process specified by process ID pid or job specification jobspec exits and return the exit status of the last command waited for. If a job spec is given, all processes in the job are waited for. If no arguments are given, all currently active child processes are waited for, and the return status is zero. If neither jobspec nor pid specifies an active child process of the shell, the return status is 127. % Bash Shell - Job Control Builtins disown disown [-ar] [-h] [jobspec...] Without options, each jobspec is removed from the table of active jobs. If the `-h' option is given, the job is not removed from the table, but is marked so that SIGHUP is not sent to the job if the shell receives a SIGHUP. If jobspec is not present, and neither the `-a' nor `-r' option is supplied, the current job is used. If no jobspec is supplied, the `-a' option means to remove or mark all jobs; the `-r' option without a jobspec argument restricts operation to running jobs. % Bash Shell - Job Control Builtins suspend suspend [-f] Suspend the execution of this shell until it receives a SIGCONT signal. The `-f' option means to suspend even if the shell is a login shell. When job control is not active, the kill and wait builtins do not accept jobspec arguments. They must be supplied process IDs. % Bash Shell - Job Control Variables auto_resume This variable controls how the shell interacts with the user and job control. If this variable exists then single word simple commands without redirections are treated as candidates for resumption of an existing job. There is no ambiguity allowed; if there is more than one job beginning with the string typed, then the most recently accessed job will be selected. The name of a stopped job, in this context, is the command line used to start it. If this variable is set to the value `exact', the string supplied must match the name of a stopped job exactly; if set to `substring', the string supplied needs to match a substring of the name of a stopped job. The `substring' value provides functionality analogous to the `%?' job ID. If set to any other value, the supplied string must be a prefix of a stopped job's name; this provides functionality analogous to the `%' job ID. % Bash Shell - Command Line Editing C-b Move back one character. % Bash Shell - Command Line Editing C-f Move forward one character. % Bash Shell - Command Line Editing DEL or Backspace Delete the character to the left of the cursor. % Bash Shell - Command Line Editing C-d Delete the character underneath the cursor. % Bash Shell - Command Line Editing Printing characters Insert the character into the line at the cursor. % Bash Shell - Command Line Editing C-_ or C-x C-u Undo the last editing command. You can undo all the way back to an empty line. (Depending on your configuration, the Backspace key be set to delete the character to the left of the cursor and the DEL key set to delete the character underneath the cursor, like C-d, rather than the character to the left of the cursor.) % Bash Shell - Command Line Editing C-a Move to the start of the line. % Bash Shell - Command Line Editing C-e Move to the end of the line. % Bash Shell - Command Line Editing M-f Move forward a word, where a word is composed of letters and digits. % Bash Shell - Command Line Editing M-b Move backward a word. % Bash Shell - Command Line Editing C-l Clear the screen, reprinting the current line at the top. % Bash Shell - Command Line Editing C-k Kill the text from the current cursor position to the end of the line. % Bash Shell - Command Line Editing M-d Kill from the cursor to the end of the current word, or, if between words, to the end of the next word. Word boundaries are the same as those used by M-f. % Bash Shell - Command Line Editing M-DEL Kill from the cursor the start of the current word, or, if between words, to the start of the previous word. Word boundaries are the same as those used by M-b. % Bash Shell - Command Line Editing C-w Kill from the cursor to the previous whitespace. This is different than M-DEL because the word boundaries differ. Here is how to yank the text back into the line. Yanking means to copy the most-recently-killed text from the kill buffer. % Bash Shell - Command Line Editing C-y Yank the most recently killed text back into the buffer at the cursor. % Bash Shell - Command Line Editing M-y Rotate the kill-ring, and yank the new top. You can only do this if the prior command is C-y or M-y. % Bash Shell - Readline Arguments You can pass numeric arguments to Readline commands. Sometimes the argument acts as a repeat count, other times it is the sign of the argument that is significant. If you pass a negative argument to a command which normally acts in a forward direction, that command will act in a backward direction. For example, to kill text back to the start of the line, you might type `M--C-k'. % Bash Shell - Readline Arguments The general way to pass numeric arguments to a command is to type meta digits before the command. If the first `digit' typed is a minus sign (`-'), then the sign of the argument will be negative. Once you have typed one meta digit to get the argument started, you can type the remainder of the digits, and then the command. For example, to give the C-d command an argument of 10, you could type `M-1 0 C-d', which will delete the next ten characters on the input line. % Bash Shell - Searching for Commands in the History Readline provides commands for searching through the command history for lines containing a specified string. There are two search modes: incremental and non-incremental. % Bash Shell - Searching for Commands in the History Incremental history searches begin before the user has finished typing the search string. As each character of the search string is typed, Readline displays the next entry from the history matching the string typed so far. An incremental search requires only as many characters as needed to find the desired history entry. To search backward in the history for a particular string, type C- r. Typing C-s searches forward through the history. The characters present in the value of the isearch-terminators variable are used to terminate an incremental search. If that variable has not been assigned a value, the ESC and C-J characters will terminate an incremental search. % Bash Shell - Searching for Commands in the History C-g will abort an incremental history search and restore the original line. When the search is terminated, the history entry containing the search string becomes the current line. % Bash Shell - Searching for Commands in the History To find other matching entries in the history list, type C-r or C-s as appropriate. This will search backward or forward in the history for the next entry matching the search string typed so far. % Bash Shell - Searching for Commands in the History Any other key sequence bound to a Readline command will terminate the search and execute that command. For instance, a RET will terminate the search and accept the line, thereby executing the command from the history list. A movement command will terminate the search, make the last line found the current line, and begin editing. % Bash Shell - Searching for Commands in the History Readline remembers the last incremental history search string. If two C-rs are typed without any intervening characters defining a new search string, any remembered search string is used. % Bash Shell - Searching for Commands in the History Non-incremental history searches read the entire search string before starting to search for matching history lines. The search string may be typed by the user or be part of the contents of the current line. % Bash Shell - Readline Init File Although the Readline library comes with a set of Emacs-like keybindings installed by default, it is possible to use a different set of keybindings. Any user can customize programs that use % Bash Shell - Readline Init File - ~/.inputrc Readline by putting commands in an inputrc file, conventionally in his home directory. The name of this file is taken from the value of the shell variable INPUTRC. If that variable is unset, the default is `~/.inputrc'. % Bash Shell - Readline Init File - ~/.inputrc When a program which uses the Readline library starts up, the init file is read, and the key bindings are set. % Bash Shell - Readline Init File - ~/.inputrc In addition, the C-x C-r command re-reads the init file, thus incorporating any changes that you might have made to it. % Bash Shell - Readline Init File Syntax - ~/.inputrc Lines beginning with a `#' are comments. Lines beginning with a `$' indicate conditional constructs. Other lines denote variable settings and key bindings. Variable Settings You can modify the run-time behavior of Readline by altering the values of variables in Readline using the set command within the init file. % Bash Shell - Readline Init File Syntax - ~/.inputrc set variable value Here, for example, is how to change from the default Emacs-like key binding to use vi line editing commands: % Bash Shell - Readline Init File Syntax - ~/.inputrc set editing-mode vi Variable names and values, where appropriate, are recognized without regard to case. The bind -V command lists the current Readline variable names and values. A great deal of run-time behavior is changeable with the following variables. % Bash Shell - Readline Init File Syntax - ~/.inputrc bell-style Controls what happens when Readline wants to ring the terminal bell. If set to `none', Readline never rings the bell. If set to `visible', Readline uses a visible bell if one is available. If set to `audible' (the default), Readline attempts to ring the terminal's bell. % Bash Shell - Readline Init File Syntax - ~/.inputrc comment-begin The string to insert at the beginning of the line when the insert-comment command is executed. The default value is "#". % Bash Shell - Readline Init File Syntax - ~/.inputrc completion-ignore-case If set to `on', Readline performs filename matching and completion in a case- insensitive fashion. The default value is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc completion-query-items The number of possible completions that determines when the user is asked whether he wants to see the list of possibilities. If the number of possible completions is greater than this value, Readline will ask the user whether or not he wishes to view them; otherwise, they are simply listed. This variable must be set to an integer value greater than or equal to 0. The default limit is 100. % Bash Shell - Readline Init File Syntax - ~/.inputrc convert-meta If set to `on', Readline will convert characters with the eighth bit set to an ASCII key sequence by stripping the eighth bit and prefixing an ESC character, converting them to a meta-prefixed key sequence. The default value is `on'. % Bash Shell - Readline Init File Syntax - ~/.inputrc disable-completion If set to `On', Readline will inhibit word completion. Completion characters will be inserted into the line as if they had been mapped to self-insert. The default is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc editing-mode The editing-mode variable controls which default set of key bindings is used. By default, Readline starts up in Emacs editing mode, where the keystrokes are most similar to Emacs. This variable can be set to either `emacs' or `vi'. % Bash Shell - Readline Init File Syntax - ~/.inputrc enable-keypad When set to `on', Readline will try to enable the application keypad when it is called. Some systems need this to enable the arrow keys. The default is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc expand-tilde If set to `on', tilde expansion is performed when Readline attempts word completion. The default is `off'. If set to `on', the history code attempts to place point at the same location on each history line retrived with previous-history or next-history. % Bash Shell - Readline Init File Syntax - ~/.inputrc horizontal-scroll-mode This variable can be set to either `on' or `off'. Setting it to `on' means that the text of the lines being edited will scroll horizontally on a single screen line when they are longer than the width of the screen, instead of wrapping onto a new screen line. By default, this variable is set to `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc input-meta If set to `on', Readline will enable eight-bit input (it will not clear the eighth bit in the characters it reads), regardless of what the terminal claims it can support. The default value is `off'. The name meta-flag is a synonym for this variable. % Bash Shell - Readline Init File Syntax - ~/.inputrc isearch-terminators The string of characters that should terminate an incremental search without subsequently executing the character as a command. If this variable has not been given a value, the characters ESC and C-J will terminate an incremental search. % Bash Shell - Readline Init File Syntax - ~/.inputrc keymap Sets Readline's idea of the current keymap for key binding commands. Acceptable keymap names are emacs, emacs-standard, emacs-meta, emacs-ctlx, vi, vi- move, vi-command, and vi-insert. vi is equivalent to vi-command; emacs is equivalent to emacs-standard. The default value is emacs. The value of the editing-mode variable also affects the default keymap. % Bash Shell - Readline Init File Syntax - ~/.inputrc mark-directories If set to `on', completed directory names have a slash appended. The default is `on'. % Bash Shell - Readline Init File Syntax - ~/.inputrc mark-modified-lines This variable, when set to `on', causes Readline to display an asterisk (`*') at the start of history lines which have been modified. This variable is `off' by default. % Bash Shell - Readline Init File Syntax - ~/.inputrc mark-symlinked-directories If set to `on', completed names which are symbolic links to directories have a slash appended (subject to the value of mark-directories). The default is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc match-hidden-files This variable, when set to `on', causes Readline to match files whose names begin with a `.' (hidden files) when performing filename completion, unless the leading `.' is supplied by the user in the filename to be completed. This variable is `on' by default. % Bash Shell - Readline Init File Syntax - ~/.inputrc output-meta If set to `on', Readline will display characters with the eighth bit set directly rather than as a meta-prefixed escape sequence. The default is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc page-completions If set to `on', Readline uses an internal more-like pager to display a screenful of possible completions at a time. This variable is `on' by default. % Bash Shell - Readline Init File Syntax - ~/.inputrc print-completions-horizontally If set to `on', Readline will display completions with matches sorted horizontally in alphabetical order, rather than down the screen. The default is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc show-all-if-ambiguous This alters the default behavior of the completion functions. If set to `on', words which have more than one possible completion cause the matches to be listed immediately instead of ringing the bell. The default value is `off'. % Bash Shell - Readline Init File Syntax - ~/.inputrc visible-stats If set to `on', a character denoting a file's type is appended to the filename when listing possible completions. The default is `off'. % Bash Shell - Key Bindings The syntax for controlling key bindings in the init file is simple. First you need to find the name of the command that you want to change. Once you know the name of the command, simply place on a line in the init file the name of the key you wish to bind the command to, a colon, and then the name of the command. The name of the key can be expressed in different ways, depending on what you find most comfortable. % Bash Shell - Key Bindings In addition to command names, readline allows keys to be bound to a string that is inserted when the key is pressed (a macro). % Bash Shell - Key Bindings The bind -p command displays Readline function names and bindings in a format that can put directly into an initialization file. keyname: function-name or macro keyname is the name of a key spelled out in English. For example: Control-u: universal-argument Meta-Rubout: backward-kill-word Control-o: "> output" In the above example, C-u is bound to the function universal-argument, M-DEL is bound to the function backward-kill-word, and C-o is bound to run the macro expressed on the right hand side (that is, to insert the text `> output' into the line). % Bash Shell - Key Bindings A number of symbolic character names are recognized while processing this key binding syntax: DEL, ESC, ESCAPE, LFD, NEWLINE, RET, RETURN, RUBOUT, SPACE, SPC, and TAB. "keyseq": function-name or macro keyseq differs from keyname above in that strings denoting an entire key sequence can be specified, by placing the key sequence in double quotes. Some GNU Emacs style key escapes can be used, as in the following example, but the special character names are not recognized. "\C-u": universal-argument "\C-x\C-r": re-read-init-file "\e[11~": "Function Key 1" In the above example, C-u is again bound to the function universal-argument (just as it was in the first example), `C-x C-r' is bound to the function re-read-init- file, and `ESC [ 1 1 ~' is bound to insert the text `Function Key 1'. % Bash Shell - Key Bindings - escape sequences \C- control prefix % Bash Shell - Key Bindings - escape sequences \M- meta prefix % Bash Shell - Key Bindings - escape sequences \e an escape character % Bash Shell - Key Bindings - escape sequences \\ backslash % Bash Shell - Key Bindings - escape sequences \" ", a double quotation mark % Bash Shell - Key Bindings - escape sequences \' ', a single quote or apostrophe % Bash Shell - Key Bindings - escape sequences \a alert (bell) % Bash Shell - Key Bindings - escape sequences \b backspace % Bash Shell - Key Bindings - escape sequences \d delete % Bash Shell - Key Bindings - escape sequences \f form feed % Bash Shell - Key Bindings - escape sequences \n newline % Bash Shell - Key Bindings - escape sequences \r carriage return % Bash Shell - Key Bindings - escape sequences \t horizontal tab % Bash Shell - Key Bindings - escape sequences \v vertical tab % Bash Shell - Key Bindings - escape sequences \nnn the eight-bit character whose value is the octal value nnn (one to three digits) % Bash Shell - Key Bindings - escape sequences \xHH the eight-bit character whose value is the hexadecimal value HH (one or two hex digits) % Bash Shell - Key Bindings - escape sequences When entering the text of a macro, single or double quotes must be used to indicate a macro definition. Unquoted text is assumed to be a function name. In the macro body, the backslash escapes described above are expanded. Backslash will quote any other character in the macro text, including `"' and `''. For example, the following binding will make `C-x \' insert a single `\' into the line: "\C-x\\": "\\" % Bash Shell - Conditional Init Constructs Readline implements a facility similar in spirit to the conditional compilation features of the C preprocessor which allows key bindings and variable settings to be performed as the result of tests. There are four parser directives used. $if mode term application % Bash Shell - Conditional Init Constructs $if The $if construct allows bindings to be made based on the editing mode, the terminal being used, or the application using Readline. The text of the test extends to the end of the line; no characters are required to isolate it. % Bash Shell - Conditional Init Constructs mode The mode= form of the $if directive is used to test whether Readline is in emacs or vi mode. This may be used in conjunction with the `set keymap' command, for instance, to set bindings in the emacs-standard and emacs-ctlx keymaps only if Readline is starting out in emacs mode. % Bash Shell - Conditional Init Constructs term The term= form may be used to include terminal-specific key bindings, perhaps to bind the key sequences output by the terminal's function keys. The word on the right side of the `=' is tested against both the full name of the terminal and the portion of the terminal name before the first `-'. This allows sun to match both sun and sun-cmd, for instance. % Bash Shell - Conditional Init Constructs application The application construct is used to include application-specific settings. Each program using the Readline library sets the application name, and you can test for a particular value. This could be used to bind key sequences to functions useful for a specific program. % Bash Shell - Conditional Init Constructs The following command adds a key sequence that quotes the current or previous word in Bash: $if Bash# Quote the current or previous word"\C-xq": "\eb\"\ef\""$endif $endif This command, as seen in the previous example, terminates an $if command. $else Commands in this branch of the $if directive are executed if the test fails. % Bash Shell - Conditional Init Constructs $include This directive takes a single filename as an argument and reads commands and bindings from that file. For example, the following directive reads from `/etc/inputrc': $include /etc/inputrc % Bash Shell - Command Line Editing - Commands For Moving beginning-of-line (C-a) Move to the start of the current line. % Bash Shell - Command Line Editing - Commands For Moving end-of-line (C-e) Move to the end of the line. % Bash Shell - Command Line Editing - Commands For Moving forward-char (C-f) Move forward a character. % Bash Shell - Command Line Editing - Commands For Moving backward-char (C-b) Move back a character. % Bash Shell - Command Line Editing - Commands For Moving forward-word (M-f) Move forward to the end of the next word. Words are composed of letters and digits. % Bash Shell - Command Line Editing - Commands For Moving backward-word (M-b) Move back to the start of the current or previous word. Words are composed of letters and digits. % Bash Shell - Command Line Editing - Commands For Moving clear-screen (C-l) Clear the screen and redraw the current line, leaving the current line at the top of the screen. % Bash Shell - Command Line Editing - Commands For Moving redraw-current-line () Refresh the current line. By default, this is unbound. % Bash Shell - Command Line Editing - Manipulating the History accept-line (Newline or Return) Accept the line regardless of where the cursor is. If this line is non-empty, add it to the history list according to the setting of the HISTCONTROL and HISTIGNORE variables. If this line is a modified history line, then restore the history line to its original state. % Bash Shell - Command Line Editing - Manipulating the History previous-history (C-p) Move `back' through the history list, fetching the previous command. % Bash Shell - Command Line Editing - Manipulating the History next-history (C-n) Move `forward' through the history list, fetching the next command. % Bash Shell - Command Line Editing - Manipulating the History beginning-of-history (M-<) Move to the first line in the history. % Bash Shell - Command Line Editing - Manipulating the History end-of-history (M->) Move to the end of the input history, i.e., the line currently being entered. % Bash Shell - Command Line Editing - Manipulating the History reverse-search-history (C-r) Search backward starting at the current line and moving `up' through the history as necessary. This is an incremental search. % Bash Shell - Command Line Editing - Manipulating the History forward-search-history (C-s) Search forward starting at the current line and moving `down' through the the history as necessary. This is an incremental search. % Bash Shell - Command Line Editing - Manipulating the History non-incremental-reverse-search-history (M-p) Search backward starting at the current line and moving `up' through the history as necessary using a non-incremental search for a string supplied by the user. % Bash Shell - Command Line Editing - Manipulating the History non-incremental-forward-search-history (M-n) Search forward starting at the current line and moving `down' through the the history as necessary using a non-incremental search for a string supplied by the user. % Bash Shell - Command Line Editing - Manipulating the History history-search-forward () Search forward through the history for the string of characters between the start of the current line and the point. This is a non-incremental search. By default, this command is unbound. % Bash Shell - Command Line Editing - Manipulating the History history-search-backward () Search backward through the history for the string of characters between the start of the current line and the point. This is a non-incremental search. By default, this command is unbound. % Bash Shell - Command Line Editing - Manipulating the History yank-nth-arg (M-C-y) Insert the first argument to the previous command (usually the second word on the previous line) at point. With an argument n, insert the nth word from the previous command (the words in the previous command begin with word 0). A negative argument inserts the nth word from the end of the previous command. % Bash Shell - Command Line Editing - Manipulating the History yank-last-arg (M-. or M-_) Insert last argument to the previous command (the last word of the previous history entry). With an argument, behave exactly like yank-nth-arg. Successive calls to yank-last-arg move back through the history list, inserting the last argument of each line in turn. % Bash Shell - Command Line Editing - Commands For Changing Text delete-char (C-d) Delete the character at point. If point is at the beginning of the line, there are no characters in the line, and the last character typed was not bound to delete-char, then return EOF. % Bash Shell - Command Line Editing - Commands For Changing Text backward-delete-char (Rubout) Delete the character behind the cursor. A numeric argument means to kill the characters instead of deleting them. % Bash Shell - Command Line Editing - Commands For Changing Text forward-backward-delete-char () Delete the character under the cursor, unless the cursor is at the end of the line, in which case the character behind the cursor is deleted. By default, this is not bound to a key. % Bash Shell - Command Line Editing - Commands For Changing Text quoted-insert (C-q or C-v) Add the next character typed to the line verbatim. This is how to insert key sequences like C-q, for example. % Bash Shell - Command Line Editing - Commands For Changing Text self-insert (a, b, A, 1, !, ...) Insert yourself. % Bash Shell - Command Line Editing - Commands For Changing Text transpose-chars (C-t) Drag the character before the cursor forward over the character at the cursor, moving the cursor forward as well. If the insertion point is at the end of the line, then this transposes the last two characters of the line. Negative arguments have no effect. % Bash Shell - Command Line Editing - Commands For Changing Text transpose-words (M-t) Drag the word before point past the word after point, moving point past that word as well. If the insertion point is at the end of the line, this transposes the last two words on the line. % Bash Shell - Command Line Editing - Commands For Changing Text upcase-word (M-u) Uppercase the current (or following) word. With a negative argument, uppercase the previous word, but do not move the cursor. % Bash Shell - Command Line Editing - Commands For Changing Text downcase-word (M-l) Lowercase the current (or following) word. With a negative argument, lowercase the previous word, but do not move the cursor. % Bash Shell - Command Line Editing - Commands For Changing Text capitalize-word (M-c) Capitalize the current (or following) word. With a negative argument, capitalize the previous word, but do not move the cursor. % Bash Shell - Command Line Editing - Commands For Changing Text overwrite-mode () Toggle overwrite mode. With an explicit positive numeric argument, switches to overwrite mode. With an explicit non-positive numeric argument, switches to insert mode. This command affects only emacs mode; vi mode does overwrite differently. Each call to readline() starts in insert mode. In overwrite mode, characters bound to self-insert replace the text at point rather than pushing the text to the right. Characters bound to backward-delete-char replace the character before point with a space. By default, this command is unbound. % Bash Shell - Command Line Editing - Killing And Yanking kill-line (C-k) Kill the text from point to the end of the line. % Bash Shell - Command Line Editing - Killing And Yanking backward-kill-line (C-x Rubout) Kill backward to the beginning of the line. % Bash Shell - Command Line Editing - Killing And Yanking unix-line-discard (C-u) Kill backward from the cursor to the beginning of the current line. % Bash Shell - Command Line Editing - Killing And Yanking kill-whole-line () Kill all characters on the current line, no matter where point is. By default, this is unbound. % Bash Shell - Command Line Editing - Killing And Yanking kill-word (M-d) Kill from point to the end of the current word, or if between words, to the end of the next word. Word boundaries are the same as forward-word. % Bash Shell - Command Line Editing - Killing And Yanking backward-kill-word (M-DEL) Kill the word behind point. Word boundaries are the same as backward-word. % Bash Shell - Command Line Editing - Killing And Yanking unix-word-rubout (C-w) Kill the word behind point, using white space as a word boundary. The killed text is saved on the kill-ring. % Bash Shell - Command Line Editing - Killing And Yanking delete-horizontal-space () Delete all spaces and tabs around point. By default, this is unbound. % Bash Shell - Command Line Editing - Killing And Yanking kill-region () Kill the text in the current region. By default, this command is unbound. % Bash Shell - Command Line Editing - Killing And Yanking copy-region-as-kill () Copy the text in the region to the kill buffer, so it can be yanked right away. By default, this command is unbound. % Bash Shell - Command Line Editing - Killing And Yanking copy-backward-word () Copy the word before point to the kill buffer. The word boundaries are the same as backward-word. By default, this command is unbound. % Bash Shell - Command Line Editing - Killing And Yanking copy-forward-word () Copy the word following point to the kill buffer. The word boundaries are the same as forward-word. By default, this command is unbound. % Bash Shell - Command Line Editing - Killing And Yanking yank (C-y) Yank the top of the kill ring into the buffer at point. % Bash Shell - Command Line Editing - Killing And Yanking yank-pop (M-y) Rotate the kill-ring, and yank the new top. You can only do this if the prior command is yank or yank-pop. % Bash Shell - Command Line Editing - Specifying Numeric Arguments digit-argument (M-0, M-1, ... M--) Add this digit to the argument already accumulating, or start a new argument. M-- starts a negative argument. % Bash Shell - Command Line Editing - Specifying Numeric Arguments universal-argument () This is another way to specify an argument. If this command is followed by one or more digits, optionally with a leading minus sign, those digits define the argument. If the command is followed by digits, executing universal-argument again ends the numeric argument, but is otherwise ignored. As a special case, if this command is immediately followed by a character that is neither a digit or minus sign, the argument count for the next command is multiplied by four. The argument count is initially one, so executing this function the first time makes the argument count four, a second time makes the argument count sixteen, and so on. By default, this is not bound to a key. % Bash Shell - Command Line Editing - Letting Readline Type For You complete (TAB) Attempt to perform completion on the text before point. The actual completion performed is application-specific. Bash attempts completion treating the text as a variable (if the text begins with `$'), username (if the text begins with `~'), hostname (if the text begins with `@'), or command (including aliases and functions) in turn. If none of these produces a match, filename completion is attempted. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-completions (M-?) List the possible completions of the text before point. % Bash Shell - Command Line Editing - Letting Readline Type For You insert-completions (M-*) Insert all completions of the text before point that would have been generated by possible-completions. % Bash Shell - Command Line Editing - Letting Readline Type For You menu-complete () Similar to complete, but replaces the word to be completed with a single match from the list of possible completions. Repeated execution of menu-complete steps through the list of possible completions, inserting each match in turn. At the end of the list of completions, the bell is rung (subject to the setting of bell-style) and the original text is restored. An argument of n moves n positions forward in the list of matches; a negative argument may be used to move backward through the list. This command is intended to be bound to TAB, but is unbound by default. % Bash Shell - Command Line Editing - Letting Readline Type For You delete-char-or-list () Deletes the character under the cursor if not at the beginning or end of the line (like delete-char). If at the end of the line, behaves identically to possible- completions. This command is unbound by default. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-filename (M-/) Attempt filename completion on the text before point. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-filename-completions (C-x /) List the possible completions of the text before point, treating it as a filename. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-username (M-~) Attempt completion on the text before point, treating it as a username. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-username-completions (C-x ~) List the possible completions of the text before point, treating it as a username. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-variable (M-$) Attempt completion on the text before point, treating it as a shell variable. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-variable-completions (C-x $) List the possible completions of the text before point, treating it as a shell variable. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-hostname (M-@) Attempt completion on the text before point, treating it as a hostname. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-hostname-completions (C-x @) List the possible completions of the text before point, treating it as a hostname. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-command (M-!) Attempt completion on the text before point, treating it as a command name. Command completion attempts to match the text against aliases, reserved words, shell functions, shell builtins, and finally executable filenames, in that order. % Bash Shell - Command Line Editing - Letting Readline Type For You possible-command-completions (C-x !) List the possible completions of the text before point, treating it as a command name. % Bash Shell - Command Line Editing - Letting Readline Type For You dynamic-complete-history (M-TAB) Attempt completion on the text before point, comparing the text against lines from the history list for possible completion matches. % Bash Shell - Command Line Editing - Letting Readline Type For You complete-into-braces (M-{) Perform filename completion and insert the list of possible completions enclosed within braces so the list is available to the shell. % Bash Shell - Command Line Editing - Keyboard Macros start-kbd-macro (C-x () Begin saving the characters typed into the current keyboard macro. % Bash Shell - Command Line Editing - Keyboard Macros end-kbd-macro (C-x )) Stop saving the characters typed into the current keyboard macro and save the definition. call-last-kbd-macro (C-x e) Re-execute the last keyboard macro defined, by making the characters in the macro appear as if typed at the keyboard. % Bash Shell - Command Line Editing - Some Miscellaneous Commands re-read-init-file (C-x C-r) Read in the contents of the inputrc file, and incorporate any bindings or variable assignments found there. % Bash Shell - Command Line Editing - Some Miscellaneous Commands abort (C-g) Abort the current editing command and ring the terminal's bell (subject to the setting of bell-style). % Bash Shell - Command Line Editing - Some Miscellaneous Commands do-uppercase-version (M-a, M-b, M-x, ...) If the metafied character x is lowercase, run the command that is bound to the corresponding uppercase character. % Bash Shell - Command Line Editing - Some Miscellaneous Commands prefix-meta (ESC) Metafy the next character typed. This is for keyboards without a meta key. Typing `ESC f' is equivalent to typing M-f. % Bash Shell - Command Line Editing - Some Miscellaneous Commands undo (C-_ or C-x C-u) Incremental undo, separately remembered for each line. % Bash Shell - Command Line Editing - Some Miscellaneous Commands revert-line (M-r) Undo all changes made to this line. This is like executing the undo command enough times to get back to the beginning. % Bash Shell - Command Line Editing - Some Miscellaneous Commands tilde-expand (M-&) Perform tilde expansion on the current word. % Bash Shell - Command Line Editing - Some Miscellaneous Commands set-mark (C-@) Set the mark to the point. If a numeric argument is supplied, the mark is set to that position. % Bash Shell - Command Line Editing - Some Miscellaneous Commands exchange-point-and-mark (C-x C-x) Swap the point with the mark. The current cursor position is set to the saved position, and the old cursor position is saved as the mark. % Bash Shell - Command Line Editing - Some Miscellaneous Commands character-search (C-]) A character is read and point is moved to the next occurrence of that character. A negative count searches for previous occurrences. % Bash Shell - Command Line Editing - Some Miscellaneous Commands character-search-backward (M-C-]) A character is read and point is moved to the previous occurrence of that character. A negative count searches for subsequent occurrences. % Bash Shell - Command Line Editing - Some Miscellaneous Commands insert-comment (M-#) Without a numeric argument, the value of the comment-begin variable is inserted at the beginning of the current line. If a numeric argument is supplied, this command acts as a toggle: if the characters at the beginning of the line do not match the value of comment- begin, the value is inserted, otherwise the characters in comment-begin are deleted from the beginning of the line. In either case, the line is accepted as if a newline had been typed. The default value of comment-begin causes this command to make the current line a shell comment. If a numeric argument causes the comment character to be removed, the line will be executed by the shell. % Bash Shell - Command Line Editing - Some Miscellaneous Commands dump-functions () Print all of the functions and their key bindings to the Readline output stream. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file. This command is unbound by default. % Bash Shell - Command Line Editing - Some Miscellaneous Commands dump-variables () Print all of the settable variables and their values to the Readline output stream. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file. This command is unbound by default. % Bash Shell - Command Line Editing - Some Miscellaneous Commands dump-macros () Print all of the Readline key sequences bound to macros and the strings they output. If a numeric argument is supplied, the output is formatted in such a way that it can be made part of an inputrc file. This command is unbound by default. % Bash Shell - Command Line Editing - Some Miscellaneous Commands glob-complete-word (M-g) The word before point is treated as a pattern for pathname expansion, with an asterisk implicitly appended. This pattern is used to generate a list of matching file names for possible completions. % Bash Shell - Command Line Editing - Some Miscellaneous Commands glob-expand-word (C-x *) The word before point is treated as a pattern for pathname expansion, and the list of matching file names is inserted, replacing the word. If a numeric argument is supplied, a `*' is appended before pathname expansion. % Bash Shell - Command Line Editing - Some Miscellaneous Commands glob-list-expansions (C-x g) The list of expansions that would have been generated by glob-expand-word is displayed, and the line is redrawn. If a numeric argument is supplied, a `*' is appended before pathname expansion. % Bash Shell - Command Line Editing - Some Miscellaneous Commands display-shell-version (C-x C-v) Display version information about the current instance of Bash. % Bash Shell - Command Line Editing - Some Miscellaneous Commands shell-expand-line (M-C-e) Expand the line as the shell does. This performs alias and history expansion as well as all of the shell word expansions. % Bash Shell - Command Line Editing - Some Miscellaneous Commands history-expand-line (M-^) Perform history expansion on the current line. % Bash Shell - Command Line Editing - Some Miscellaneous Commands magic-space () Perform history expansion on the current line and insert a space. % Bash Shell - Command Line Editing - Some Miscellaneous Commands alias-expand-line () Perform alias expansion on the current line. % Bash Shell - Command Line Editing - Some Miscellaneous Commands history-and-alias-expand-line () Perform history and alias expansion on the current line. % Bash Shell - Command Line Editing - Some Miscellaneous Commands insert-last-argument (M-. or M-_) A synonym for yank-last-arg. % Bash Shell - Command Line Editing - Some Miscellaneous Commands operate-and-get-next (C-o) Accept the current line for execution and fetch the next line relative to the current line from the history for editing. Any argument is ignored. edit-and-execute-command (C-xC-e) Invoke an editor on the current command line, and execute the result as shell commands. Bash attempts to invoke $FCEDIT, $EDITOR, and emacs as the editor, in that order. % Bash Shell - Command Line Editing - Readline vi Mode While the Readline library does not have a full set of vi editing functions, it does contain enough to allow simple editing of the line. The Readline vi mode behaves as specified in the POSIX 1003.2 standard. % Bash Shell - Command Line Editing - Readline vi Mode In order to switch interactively between emacs and vi editing modes, use the `set -o emacs' and `set -o vi' commands. The Readline default is emacs mode. % Bash Shell - Command Line Editing - Readline vi Mode When you enter a line in vi mode, you are already placed in `insertion' mode, as if you had typed an `i'. Pressing ESC switches you into `command' mode, where you can edit the text of the line with the standard vi movement keys, move to previous history lines with `k' and subsequent lines with `j', and so forth. % Bash Shell - Command Line Editing - Programmable Completion When word completion is attempted for an argument to a command for which a completion specification (a compspec) has been defined using the complete builtin, the programmable completion facilities are invoked. % Bash Shell - Command Line Editing - Programmable Completion First, the command name is identified. If a compspec has been defined for that command, the compspec is used to generate the list of possible completions for the word. If the command word is a full pathname, a compspec for the full pathname is searched for first. If no compspec is found for the full pathname, an attempt is made to find a compspec for the portion following the final slash. % Bash Shell - Command Line Editing - Programmable Completion Once a compspec has been found, it is used to generate the list of matching words. If a compspec is not found, the default Bash completion described above is performed. % Bash Shell - Command Line Editing - Programmable Completion First, the actions specified by the compspec are used. Only matches which are prefixed by the word being completed are returned. When the `-f' or `-d' option is used for filename or directory name completion, the shell variable FIGNORE is used to filter the matches. % Bash Shell - Command Line Editing - Programmable Completion Any completions specified by a filename expansion pattern to the `-G' option are generated next. The words generated by the pattern need not match the word being completed. The % Bash Shell - Command Line Editing - Programmable Completion GLOBIGNORE shell variable is not used to filter the matches, but the FIGNORE shell variable is used. % Bash Shell - Command Line Editing - Programmable Completion The string specified as the argument to the `-W' option is considered. The string is first split using the characters in the IFS special variable as delimiters. Shell quoting is honored. Each word is then expanded using brace expansion, tilde expansion, parameter and variable expansion, command substitution, arithmetic expansion, and pathname expansion, as described above. The results are split using the rules described above. The results of the expansion are prefix-matched against the word being completed, and the matching words become the possible completions. % Bash Shell - Command Line Editing - Programmable Completion After matches have been generated, any shell function or command specified with the `- F' and `-C' options is invoked. When the command or function is invoked, the COMP_LINE and COMP_POINT variables are assigned values as described above. If a shell function is being invoked, the COMP_WORDS and COMP_CWORD variables are also set. When the function or command is invoked, the first argument is the name of the command whose arguments are being completed, the second argument is the word being completed, and the third argument is the word preceding the word being completed on the current command line. No filtering of the generated completions against the word being completed is performed; the function or command has complete freedom in generating the matches. % Bash Shell - Command Line Editing - Programmable Completion Any function specified with `-F' is invoked first. The function may use any of the shell facilities, including the compgen builtin described below, to generate the matches. It must put the possible completions in the COMPREPLY array variable. % Bash Shell - Command Line Editing - Programmable Completion Any command specified with the `-C' option is invoked in an environment equivalent to command substitution. It should print a list of completions, one per line, to the standard output. Backslash may be used to escape a newline, if necessary. % Bash Shell - Command Line Editing - Programmable Completion After all of the possible completions are generated, any filter specified with the `-X' option is applied to the list. The filter is a pattern as used for pathname expansion; a `&' in the pattern is replaced with the text of the word being completed. A literal `&' may be escaped with a backslash; the backslash is removed before attempting a match. Any completion that matches the pattern will be removed from the list. A leading `!' negates the pattern; in this case any completion not matching the pattern will be removed. % Bash Shell - Command Line Editing - Programmable Completion Any prefix and suffix specified with the `-P' and `-S' options are added to each member of the completion list, and the result is returned to the Readline completion code as the list of possible completions. % Bash Shell - Command Line Editing - Programmable Completion If the previously-applied actions do not generate any matches, and the `-o dirnames' option was supplied to complete when the compspec was defined, directory name completion is attempted. % Bash Shell - Command Line Editing - Programmable Completion By default, if a compspec is found, whatever it generates is returned to the completion code as the full set of possible completions. The default Bash completions are not attempted, and the % Bash Shell - Command Line Editing - Programmable Completion Readline default of filename completion is disabled. If the `-o default' option was supplied to complete when the compspec was defined, Readline's default completion will be performed if the compspec generates no matches. % Bash Shell - Command Line Editing - Programmable Completion When a compspec indicates that directory name completion is desired, the programmable completion functions force Readline to append a slash to completed names which are symbolic links to directories, subject to the value of the mark-directories Readline variable, regardless of the setting of the mark-symlinked-directories Readline variable. % Bash Shell - Programmable Completion Builtins Two builtin commands are available to manipulate the programmable completion facilities. compgen complete % Bash Shell - Programmable Completion Builtins compgen [option] [word] Generate possible completion matches for word according to the options, which may be any option accepted by the complete builtin with the exception of `-p' and `- r', and write the matches to the standard output. When using the `-F' or `-C' options, the various shell variables set by the programmable completion facilities, while available, will not have useful values. % Bash Shell - Programmable Completion Builtins compgen [option] [word] The matches will be generated in the same way as if the programmable completion code had generated them directly from a completion specification with the same flags. If word is specified, only those completions matching word will be displayed. % Bash Shell - Programmable Completion Builtins compgen [option] [word] The return value is true unless an invalid option is supplied, or no matches were generated. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] Specify how arguments to each name should be completed. If the `-p' option is supplied, or if no options are supplied, existing completion specifications are printed in a way that allows them to be reused as input. The `-r' option removes a completion specification for each name, or, if no names are supplied, all completion specifications. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] The process of applying these completion specifications when word completion is attempted is described above. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] Other options, if specified, have the following meanings. The arguments to the `-G', `-W', and `-X' options (and, if necessary, the `-P' and `-S' options) should be quoted to protect them from expansion before the complete builtin is invoked. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -o comp-option The comp-option controls several aspects of the compspec's behavior beyond the simple generation of completions. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -o default Use Readline's default filename completion if the compspec generates no matches. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -o dirnames Perform directory name completion if the compspec generates no matches. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -o filenames Tell Readline that the compspec generates filenames, so it can perform any filename\- specific processing (like adding a slash to directory names or suppressing trailing spaces). This option is intended to be used with shell functions specified with `-F'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -o nospace Tell Readline not to append a space (the default) to words completed at the end of the line. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A alias Alias names. May also be specified as `-a'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A arrayvar Array variable names. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A binding Readline key binding names. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A builtin Names of shell builtin commands. May also be specified as `-b'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A command Command names. May also be specified as `-c'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A directory Directory names. May also be specified as `-d'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A disabled Names of disabled shell builtins. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A enabled Names of enabled shell builtins. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A export Names of exported shell variables. May also be specified as `-e'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A file File names. May also be specified as `-f'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A function Names of shell functions. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A group Group names. May also be specified as `-g'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A helptopic Help topics as accepted by the help builtin. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A hostname Hostnames, as taken from the file specified by the HOSTFILE shell variable. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A job Job names, if job control is active. May also be specified as `-j'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A keyword Shell reserved words. May also be specified as `-k'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A running Names of running jobs, if job control is active. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A service Service names. May also be specified as `-s'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A setopt Valid arguments for the `-o' option to the set builtin. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A shopt Shell option names as accepted by the shopt builtin. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A signal Signal names. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A stopped Names of stopped jobs, if job control is active. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A user User names. May also be specified as `-u'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -A variable Names of all shell variables. May also be specified as `-v'. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -G globpat The filename expansion pattern globpat is expanded to generate the possible completions. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -W wordlist The wordlist is split using the characters in the IFS special variable as delimiters, and each resultant word is expanded. The possible completions are the members of the resultant list which match the word being completed. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -C command command is executed in a subshell environment, and its output is used as the possible completions. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -F function The shell function function is executed in the current shell environment. When it finishes, the possible completions are retrieved from the value of the COMPREPLY array variable. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -X filterpat filterpat is a pattern as used for filename expansion. It is applied to the list of possible completions generated by the preceding options and arguments, and each completion matching filterpat is removed from the list. A leading `!' in filterpat negates the pattern; in this case, any completion not matching filterpat is removed. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -P prefix prefix is added at the beginning of each possible completion after all other options have been applied. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] -S suffix suffix is appended to each possible completion after all other options have been applied. % Bash Shell - Programmable Completion Builtins complete [-abcdefgjksuv] [-o comp-option] [-A action] [-G globpat] [-W wordlist][-P prefix] [-S suffix] [-X filterpat] [-F function][-C command] name [name ...] complete -pr [name ...] The return value is true unless an invalid option is supplied, an option other than `-p' or `-r' is supplied without a name argument, an attempt is made to remove a completion specification for a name for which no specification exists, or an error occurs adding a completion specification. % Bash Shell - Bash History Facilities When the `-o history' option to the set builtin is enabled, the shell provides access to the command history, the list of commands previously typed. The value of the HISTSIZE shell variable is used as the number of commands to save in a history list. The text of the last $HISTSIZE commands (default 500) is saved. The shell stores each command in the history list prior to parameter and variable expansion but after history expansion is performed, subject to the values of the shell variables HISTIGNORE and HISTCONTROL. % Bash Shell - Bash History Facilities When the shell starts up, the history is initialized from the file named by the HISTFILE variable (default `~/.bash_history'). The file named by the value of HISTFILE is truncated, if necessary, to contain no more than the number of lines specified by the value of the HISTFILESIZE variable. When an interactive shell exits, the last $HISTSIZE lines are copied from the history list to the file named by $HISTFILE. If the histappend shell option is set, the lines are appended to the history file, otherwise the history file is overwritten. If HISTFILE is unset, or if the history file is unwritable, the history is not saved. After saving the history, the history file is truncated to contain no more than $HISTFILESIZE lines. If HISTFILESIZE is not set, no truncation is performed. % Bash Shell - Bash History Facilities The builtin command fc may be used to list or edit and re-execute a portion of the history list. % Bash Shell - Bash History Facilities The history builtin may be used to display or modify the history list and manipulate the history file. When using command-line editing, search commands are available in each editing mode that provide access to the history list. % Bash Shell - Bash History Facilities The shell allows control over which commands are saved on the history list. The HISTCONTROL and HISTIGNORE variables may be set to cause the shell to save only a subset of the commands entered. The cmdhist shell option, if enabled, causes the shell to attempt to save each line of a multi-line command in the same history entry, adding semicolons where necessary to preserve syntactic correctness. The lithist shell option causes the shell to save the command with embedded newlines instead of semicolons. The shopt builtin is used to set these options. % Bash Shell - Bash History Builtins fc [-e ename] [-nlr] [first] [last] fc -s [pat=rep] [command] Fix Command. In the first form, a range of commands from first to last is selected from the history list. Both first and last may be specified as a string (to locate the most recent command beginning with that string) or as a number (an index into the history list, where a negative number is used as an offset from the current command number). If last is not specified it is set to first. If first is not specified it is set to the previous command for editing and -16 for listing. If the `-l' flag is given, the commands are listed on standard output. The `-n' flag suppresses the command numbers when listing. The `-r' flag reverses the order of the listing. Otherwise, the editor given by ename is invoked on a file containing those commands. If ename is not given, the value of the following variable expansion is used: ${FCEDIT:-${EDITOR:-vi}}. This says to use the value of the FCEDIT variable if set, or the value of the EDITOR variable if that is set, or vi if neither is set. When editing is complete, the edited commands are echoed and executed. % Bash Shell - Bash History Builtins fc [-e ename] [-nlr] [first] [last] fc -s [pat=rep] [command] In the second form, command is re-executed after each instance of pat in the selected command is replaced by rep. % Bash Shell - Bash History Builtins fc [-e ename] [-nlr] [first] [last] fc -s [pat=rep] [command] A useful alias to use with the fc command is r='fc -s', so that typing `r cc' runs the last command beginning with cc and typing `r' re-executes the last command. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg With no options, display the history list with line numbers. Lines prefixed with a `*' have been modified. An argument of n lists only the last n lines. Options, if supplied, have the following meanings: % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -c Clear the history list. This may be combined with the other options to replace the history list completely. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -d offset Delete the history entry at position offset. offset should be specified as it appears when the history is displayed. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -a Append the new history lines (history lines entered since the beginning of the current Bash session) to the history file. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -n Append the history lines not already read from the history file to the current history list. These are lines appended to the history file since the beginning of the current Bash session. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -r Read the current history file and append its contents to the history list. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -w Write out the current history to the history file. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -p Perform history substitution on the args and display the result on the standard output, without storing the results in the history list. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg -s The args are added to the end of the history list as a single entry. % Bash Shell - Bash History Builtins history [n] history -c history -d offset history [-anrw] [filename] history -ps arg When any of the `-w', `-r', `-a', or `-n' options is used, if filename is given, then it is used as the history file. If not, then the value of the HISTFILE variable is used. % Bash Shell - History Expansion History expansions introduce words from the history list into the input stream, making it easy to repeat commands, insert the arguments to a previous command into the current input line, or fix errors in previous commands quickly. % Bash Shell - History Expansion History expansion takes place in two parts. The first is to determine which line from the history list should be used during substitution. The second is to select portions of that line for inclusion into the current one. The line selected from the history is called the event, and the portions of that line that are acted upon are called words. Various modifiers are available to manipulate the selected words. The line is broken into words in the same fashion that Bash does, so that several words surrounded by quotes are considered one word. History expansions are introduced by the appearance of the history expansion character, which is `!' by default. Only `\' and `'' may be used to escape the history expansion character. % Bash Shell - History Expansion Several shell options settable with the shopt builtin may be used to tailor the behavior of history expansion. If the histverify shell option is enabled, and Readline is being used, history substitutions are not immediately passed to the shell parser. Instead, the expanded line is reloaded into the Readline editing buffer for further modification. If Readline is being used, and the histreedit shell option is enabled, a failed history expansion will be reloaded into the Readline editing buffer for correction. The `-p' option to the history builtin command may be used to see what a history expansion will do before using it. The `-s' option to the history builtin may be used to add commands to the end of the history list without actually executing them, so that they are available for subsequent recall. This is most useful in conjunction with Readline. % Bash Shell - History Expansion The shell allows control of the various characters used by the history expansion mechanism with the histchars variable. % Bash Shell - Event Designators ! Start a history substitution, except when followed by a space, tab, the end of the line, `=' or `('. % Bash Shell - Event Designators !n Refer to command line n. % Bash Shell - Event Designators !-n Refer to the command n lines back. % Bash Shell - Event Designators !! Refer to the previous command. This is a synonym for `!-1'. % Bash Shell - Event Designators !string Refer to the most recent command starting with string. % Bash Shell - Event Designators !?string[?] Refer to the most recent command containing string. The trailing `?' may be omitted if the string is followed immediately by a newline. % Bash Shell - Event Designators ^string1^string2^ Quick Substitution. Repeat the last command, replacing string1 with string2. Equivalent to !!:s/string1/string2/. % Bash Shell - Event Designators !# The entire command line typed so far. % Bash Shell - Word Designators Word designators are used to select desired words from the event. A `:' separates the event specification from the word designator. It may be omitted if the word designator begins with a `^', `$', `*', `-', or `%'. Words are numbered from the beginning of the line, with the first word being denoted by 0 (zero). Words are inserted into the current line separated by single spaces. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. !! designates the preceding command. When you type this, the preceding command is repeated in toto. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. !!:$ designates the last argument of the preceding command. This may be shortened to !$. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. !fi:2 designates the second argument of the most recent command starting with the letters fi. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. 0 (zero) The 0th word. For many applications, this is the command word. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. n The nth word. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. ^ The first argument; that is, word 1. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. $ The last argument. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. % The word matched by the most recent `?string?' search. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. x-y A range of words; `-y' abbreviates `0-y'. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. * All of the words, except the 0th. This is a synonym for `1-$'. It is not an error to use `*' if there is just one word in the event; the empty string is returned in that case. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. x* Abbreviates `x-$' If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - Word Designators Word designators are used to select desired words from the history event. A `:' separates the event specification from the word designator. x- Abbreviates `x-$' like `x*', but omits the last word. If a word designator is supplied without an event specification, the previous command is used as the event. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. h Remove a trailing pathname component, leaving only the head. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. t Remove all leading pathname components, leaving the tail. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. r Remove a trailing suffix of the form `.suffix', leaving the basename. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. e Remove all but the trailing suffix. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. p Print the new command but do not execute it. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. q Quote the substituted words, escaping further substitutions. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. x Quote the substituted words as with `q', but break into words at spaces, tabs, and newlines. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. s/old/new/ Substitute new for the first occurrence of old in the event line. Any delimiter may be used in place of `/'. The delimiter may be quoted in old and new with a single backslash. If `&' appears in new, it is replaced by old. A single backslash will quote the `&'. The final delimiter is optional if it is the last character on the input line. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. & Repeat the previous substitution. % Bash Shell - History Word Modifiers After the optional word designator, you can add a sequence of one or more of the following modifiers, each preceded by a `:'. g Cause changes to be applied over the entire event line. Used in conjunction with `s', as in gs/old/new/, or with `&'. % Bash Shell - Major Differences From The Bourne Bash implements essentially the same grammar, parameter and variable expansion, redirection, and quoting as the Bourne Shell. Bash uses the POSIX 1003.2 standard as the specification of how these features are to be implemented. % Bash Shell - Major Differences From The Bourne * Bash is POSIX-conformant, even where the POSIX specification differs from traditional sh behavior. % Bash Shell - Major Differences From The Bourne * Bash has multi-character invocation options. % Bash Shell - Major Differences From The Bourne * Bash has command-line editing and the bind builtin. % Bash Shell - Major Differences From The Bourne * Bash provides a programmable word completion mechanism, and two builtin commands, complete and compgen, to manipulate it. % Bash Shell - Major Differences From The Bourne * Bash has command history and the history and fc builtins to manipulate it. % Bash Shell - Major Differences From The Bourne * Bash implements csh-like history expansion. % Bash Shell - Major Differences From The Bourne * Bash has one-dimensional array variables, and the appropriate variable expansions and assignment syntax to use them. Several of the Bash builtins take options to act on arrays. Bash provides a number of built-in array variables. % Bash Shell - Major Differences From The Bourne * The $'...' quoting syntax, which expands ANSI-C backslash-escaped characters in the text between the single quotes, is supported. % Bash Shell - Major Differences From The Bourne * Bash supports the $"..." quoting syntax to do locale-specific translation of the characters between the double quotes. The `-D', `--dump-strings', and `- -dump-po-strings' invocation options list the translatable strings found in a script. % Bash Shell - Major Differences From The Bourne * Bash implements the ! keyword to negate the return value of a pipeline . Very useful when an if statement needs to act only if a test fails. % Bash Shell - Major Differences From The Bourne * Bash has the time reserved word and command timing. The display of the timing statistics may be controlled with the TIMEFORMAT variable. % Bash Shell - Major Differences From The Bourne * Bash implements the for (( expr1 ; expr2 ; expr3 )) arithmetic for command, similar to the C language. % Bash Shell - Major Differences From The Bourne * Bash includes the select compound command, which allows the generation of simple menus. % Bash Shell - Major Differences From The Bourne * Bash includes the [[ compound command, which makes conditional testing part of the shell grammar. % Bash Shell - Major Differences From The Bourne * Bash includes brace expansion and tilde expansion. % Bash Shell - Major Differences From The Bourne * Bash implements command aliases and the alias and unalias builtins . % Bash Shell - Major Differences From The Bourne * Bash provides shell arithmetic, the (( compound command, and arithmetic expansion. % Bash Shell - Major Differences From The Bourne * Variables present in the shell's initial environment are automatically exported to child processes. The Bourne shell does not normally do this unless the variables are explicitly marked using the export command. % Bash Shell - Major Differences From The Bourne * Bash includes the POSIX pattern removal `%', `#', `%%' and `##' expansions to remove leading or trailing substrings from variable values . % Bash Shell - Major Differences From The Bourne * The expansion ${#xx}, which returns the length of ${xx}, is supported . % Bash Shell - Major Differences From The Bourne * The expansion ${var:offset[:length]}, which expands to the substring of var's value of length length, beginning at offset, is present. % Bash Shell - Major Differences From The Bourne * The expansion ${var/[/]pattern[/replacement]}, which matches pattern and replaces it with replacement in the value of var, is available % Bash Shell - Major Differences From The Bourne * The expansion ${!prefix}* expansion, which expands to the names of all shell variables whose names begin with prefix, is available. % Bash Shell - Major Differences From The Bourne * Bash has indirect variable expansion using ${!word}. % Bash Shell - Major Differences From The Bourne * Bash can expand positional parameters beyond $9 using ${num}. % Bash Shell - Major Differences From The Bourne * The POSIX $() form of command substitution is implemented, and preferred to the Bourne shell's " (which is also implemented for backwards compatibility). % Bash Shell - Major Differences From The Bourne * Bash has process substitution. % Bash Shell - Major Differences From The Bourne * Bash automatically assigns variables that provide information about the current user (UID, EUID, and GROUPS), the current host (HOSTTYPE, OSTYPE, MACHTYPE, and HOSTNAME), and the instance of Bash that is running (BASH, BASH_VERSION, and BASH_VERSINFO). % Bash Shell - Major Differences From The Bourne * The IFS variable is used to split only the results of expansion, not all words. This closes a longstanding shell security hole. % Bash Shell - Major Differences From The Bourne * Bash implements the full set of POSIX 1003.2 filename expansion operators, including character classes, equivalence classes, and collating symbols. % Bash Shell - Major Differences From The Bourne * Bash implements extended pattern matching features when the extglob shell option is enabled. % Bash Shell - Major Differences From The Bourne * It is possible to have a variable and a function with the same name; sh does not separate the two name spaces. % Bash Shell - Major Differences From The Bourne * Bash functions are permitted to have local variables using the local builtin, and thus useful recursive functions may be written. % Bash Shell - Major Differences From The Bourne * Variable assignments preceding commands affect only that command, even builtins and functions. In sh, all variable assignments preceding commands are global unless the command is executed from the file system. % Bash Shell - Major Differences From The Bourne * Bash performs filename expansion on filenames specified as operands to input and output redirection operators. % Bash Shell - Major Differences From The Bourne * Bash contains the `<>' redirection operator, allowing a file to be opened for both reading and writing, and the `&>' redirection operator, for directing standard output and standard error to the same file. % Bash Shell - Major Differences From The Bourne * Bash treats a number of filenames specially when they are used in redirection operators. % Bash Shell - Major Differences From The Bourne * Bash can open network connections to arbitrary machines and services with the redirection operators. % Bash Shell - Major Differences From The Bourne * The noclobber option is available to avoid overwriting existing files with output redirection. The `>|' redirection operator may be used to override noclobber. % Bash Shell - Major Differences From The Bourne * The Bash cd and pwd builtins each take `-L' and `-P' options to switch between logical and physical modes. % Bash Shell - Major Differences From The Bourne * Bash allows a function to override a builtin with the same name, and provides access to that builtin's functionality within the function via the builtin and command builtins. % Bash Shell - Major Differences From The Bourne * The command builtin allows selective disabling of functions when command lookup is performed. % Bash Shell - Major Differences From The Bourne * Individual builtins may be enabled or disabled using the enable builtin. % Bash Shell - Major Differences From The Bourne * The Bash exec builtin takes additional options that allow users to control the contents of the environment passed to the executed command, and what the zeroth argument to the command is to be. % Bash Shell - Major Differences From The Bourne * Shell functions may be exported to children via the environment using export -f. % Bash Shell - Major Differences From The Bourne * The Bash export, readonly, and declare builtins can take a `-f' option to act on shell functions, a `-p' option to display variables with various attributes set in a format that can be used as shell input, a `-n' option to remove various variable attributes, and `name=value' arguments to set variable attributes and values simultaneously. % Bash Shell - Major Differences From The Bourne * The Bash hash builtin allows a name to be associated with an arbitrary filename, even when that filename cannot be found by searching the $PATH, using `hash -p'. % Bash Shell - Major Differences From The Bourne * Bash includes a help builtin for quick reference to shell facilities . % Bash Shell - Major Differences From The Bourne * The printf builtin is available to display formatted output. % Bash Shell - Major Differences From The Bourne * The Bash read builtin will read a line ending in `\' with the `-r' option, and will use the REPLY variable as a default if no non- option arguments are supplied. The Bash read builtin also accepts a prompt string with the `-p' option and will use Readline to obtain the line when given the `-e' option. The read builtin also has additional options to control input: the `-s' option will turn off echoing of input characters as they are read, the `-t' option will allow read to time out if input does not arrive within a specified number of seconds, the `-n' option will allow reading only a specified number of characters rather than a full line, and the `-d' option will read until a particular character rather than newline. % Bash Shell - Major Differences From The Bourne * The return builtin may be used to abort execution of scripts executed with the . or source builtins. * Bash includes the shopt builtin, for finer control of shell optional capabilities, and allows these options to be set and unset at shell invocation. % Bash Shell - Major Differences From The Bourne * Bash has much more optional behavior controllable with the set builtin . % Bash Shell - Major Differences From The Bourne * The test builtin is slightly different, as it implements the POSIX algorithm, which specifies the behavior based on the number of arguments. % Bash Shell - Major Differences From The Bourne * The trap builtin allows a DEBUG pseudo-signal specification, similar to EXIT. Commands specified with a DEBUG trap are executed after every simple command. The DEBUG trap is not inherited by shell functions unless the function has been given the trace attribute. The trap builtin allows an ERR pseudo-signal specification, similar to EXIT and DEBUG. Commands specified with an ERR trap are executed after a simple command fails, with a few exceptions. The ERR trap is not inherited by shell functions. % Bash Shell - Major Differences From The Bourne * The Bash type builtin is more extensive and gives more information about the names it finds. % Bash Shell - Major Differences From The Bourne * The Bash umask builtin permits a `-p' option to cause the output to be displayed in the form of a umask command that may be reused as input . % Bash Shell - Major Differences From The Bourne * Bash implements a csh-like directory stack, and provides the pushd, popd, and dirs builtins to manipulate it. Bash also makes the directory stack visible as the value of the DIRSTACK shell variable. % Bash Shell - Major Differences From The Bourne * Bash interprets special backslash-escaped characters in the prompt strings when interactive. % Bash Shell - Major Differences From The Bourne * Bash interprets special backslash-escaped characters in the prompt strings when interactive. % Bash Shell - Major Differences From The Bourne * The Bash restricted mode is more useful; The SVR4.2 shell restricted mode is too limited. % Bash Shell - Major Differences From The Bourne * The disown builtin can remove a job from the internal shell job table or suppress the sending of SIGHUP to a job when the shell exits as the result of a SIGHUP. % Bash Shell - Major Differences From The Bourne * The SVR4.2 shell has two privilege-related builtins (mldmode and priv) not present in Bash. % Bash Shell - Major Differences From The Bourne * Bash does not have the stop or newgrp builtins. % Bash Shell - Major Differences From The Bourne * Bash does not use the SHACCT variable or perform shell accounting. % Bash Shell - Major Differences From The Bourne * The SVR4.2 sh uses a TIMEOUT variable like Bash uses TMOUT. % Bash Shell - Implementation Differences From The SVR4.2 Shell * Bash does not fork a subshell when redirecting into or out of a shell control structure such as an if or while statement. % Bash Shell - Implementation Differences From The SVR4.2 Shell * Bash does not allow unbalanced quotes. The SVR4.2 shell will silently insert a needed closing quote at EOF under certain circumstances. This can be the cause of some hard- to-find errors. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell uses a baroque memory management scheme based on trapping SIGSEGV. If the shell is started from a process with SIGSEGV blocked (e.g., by using the system() C library function call), it misbehaves badly. % Bash Shell - Implementation Differences From The SVR4.2 Shell * In a questionable attempt at security, the SVR4.2 shell, when invoked without the `- p' option, will alter its real and effective UID and GID if they are less than some magic threshold value, commonly 100. This can lead to unexpected results. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell does not allow users to trap SIGSEGV, SIGALRM, or SIGCHLD. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell does not allow the IFS, MAILCHECK, PATH, PS1, or PS2 variables to be unset. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell treats `^' as the undocumented equivalent of `|'. % Bash Shell - Implementation Differences From The SVR4.2 Shell * Bash allows multiple option arguments when it is invoked (-x -v); the SVR4.2 shell allows only one option argument (-xv). In fact, some versions of the shell dump core if the second argument begins with a `-'. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell exits a script if any builtin fails; Bash exits a script only if one of the POSIX 1003.2 special builtins fails, and only for certain failures, as enumerated in the POSIX 1003.2 standard. % Bash Shell - Implementation Differences From The SVR4.2 Shell * The SVR4.2 shell behaves differently when invoked as jsh (it turns on job control).