Manual: ksh(1)
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ksh(1) ksh(1)
NAME
ksh - Korn shell
SYNOPSIS
ksh [-ir] [-c command_string | -s] [+ | -abCefhkmnopstuvx] [+ | -o][option
...]
| [+ | -A name] [argument ...] | [file] [argument ...]
The Korn shell is an interactive command interpreter and a command program-
ming language.
DESCRIPTION
The Korn shell carries out commands either interactively from a terminal
keyboard or from a file. The Korn shell is backward compatible with the
Bourne shell (invoked with the sh command) and contains virtually all of
the Bourne shell features, as well as several of the best features of the C
shell.
Some important features of the Korn shell are as follows:
++ Command aliasing
++ Filename substitution
++ Tilde substitution
++ Command substitution
++ Parameter substitution
++ Job control
++ Inline editing
A
script, a shell procedure, or a command file.
A simple command is a sequence of words separated by spaces or tabs. A
word is a sequence of characters that contains no unquoted spaces or tabs.
The first word in the sequence (numbered as 0), usually specifies the name
of a command. Any remaining words, with a few exceptions, are passed to
that command. A space refers to both spaces and tabs.
The value of a simple command is its exit value if it ends normally, or
(octal) 200 added to the signal number if it terminates due to a signal.
For a list of status values, see the signal() system call.
A pipeline is a sequence of one or more commands separated by a | (vertical
bar) or, for historical compatibility, by a ^ (circumflex). In a pipeline,
the standard output of each command becomes the standard input of the next
command. Each command runs as a separate process, and the shell waits for
the last command to end. A filter is a command that reads its standard
input, transforms it in some way, then writes it to its standard output. A
pipeline normally consists of a series of filters. Although the processes
in a pipeline (except the first process) can execute in parallel, they are
synchronized to the extent that each program needs to read the output of
its predecessor.
The exit value of a pipeline is the exit value of the last command.
A list is a sequence of one or more pipelines separated by ; (semicolon), &
(ampersand), && (two ampersands), or || (two vertical bars) and optionally
ended by a ; (semicolon), an & (ampersand), a |& (coprocess), or a newline.
These separators and terminators have the following effects:
; Causes sequential execution of the preceding pipeline; the shell waits
for the pipeline to finish.
& Causes asynchronous execution of the preceding pipeline; the shell does
not wait for the pipeline to finish.
&& Causes the list following it to be executed only if the preceding pipe-
line returns a 0 (zero) exit value.
|| Causes the list following it to be executed only if the preceding pipe-
line returns a nonzero exit value.
The cd command is an exception; if it returns a nonzero exit value, no
subsequent commands in a list are executed, regardless of the separator
characters.
The ; and & separators have equal precedence, as do && and ||. The
single-character separators have lower precedence than the double-character
separators. An unquoted newline character following a pipeline functions
the same as a ; (semicolon).
Comments
The shell treats as a comment any word that begins with a # character and
ignores that word and all characters following up to the next newline char-
acter.
Shell Flow Control Statements
Unless otherwise stated, the value returned by a command is that of the
last simple command executed in the command.
for identifier [in word...] ;do list ;done
Each time a for command is executed, identifier is set to the next word
taken from the in word list. If in word ... is omitted, the for com-
mand executes the do list once for each positional parameter that is
set. (See Parameter Substitution.) Execution ends when there are no
more words in the list.
select identifier [in word...] ;do list ;done
Prints on standard error (file descriptor 2), the set of words, each
preceded by a number. If in word... is omitted, then the positional
parameters are used instead. (See Parameter Substitution.) The PS3
prompt is printed and a line is read from the standard input. If this
line consists of the number of one of the listed words, then the value
of the parameter identifier is set to the word corresponding to this
number. If this line is empty, the selection list is printed again.
Otherwise, the value of the parameter identifier is set to null. The
contents of the line read from standard input is saved in the REPLY
parameter. The list is executed for each selection until a break or
End-of-File is encountered.
case word in [[(] pattern [| pattern] ...) list ;;] ... esac
Executes the list associated with the first pattern that matches word.
The form of the patterns is the same as that used for filename genera-
tion. (See Filename Generation.)
if list ;then list [elif list ;then list] ... [;else list] ;fi
Executes the list following if and, if it returns a 0 (zero) exit
status, executes the list following the first then. Otherwise, the
list following elif is executed and, if its value is 0 (zero), the list
following the next then is executed. Failing that, the else list is
executed. If no else list or then list is executed, then the if com-
mand returns a 0 (zero) exit status.
while list ;do list ;done
until list ;do list ;done
Executes the while list repeatedly, and if the exit status of the last
command in the list is 0 (zero), executes the do list; otherwise the
loop terminates. If no commands in the do list are executed, then the
while command returns a 0 (zero) exit status; until can be used in
place of while to negate the loop termination test.
(list)
Executes list in a separate environment. Note that if two adjacent
open parentheses are needed for nesting, a space must be inserted to
avoid arithmetic evaluation as described later.
{list;}
Executes list. Note that unlike the metacharacters ( and ), { and }
are reserved words and must be at the beginning of a line or after a ;
(semicolon) in order to be recognized.
[[expression]]
is TRUE. See Conditional Expressions for a description of expression.
function identifier {list;}
identifier. The body of the
function is the list of commands between { and }. (See Functions.)
time pipeline
Executes pipeline and prints the elapsed time as well as the user and
system time on standard error.
The following reserved words are recognized only when they appear, without
single or double quotes, as the first word of a command:
if for case
then while esac
else until function
elif do select
fi done time
{ } [[ ]]
Command Aliasing
The first word of each command is replaced by the text of an alias (if an
alias for this word was defined). The first character of an alias name can
be any nonspecial printable character, but the rest of the characters must
be the same as for a valid identifier. The replacement string can contain
any valid shell script, including the metacharacters previously listed.
The first word of each command in the replaced text, other than any that
are in the process of being replaced, is tested for aliases. If the last
character of the alias value is a space, the word following the alias will
also be checked for alias substitution.
Aliases can be used to redefine special built-in commands but cannot be
used to redefine the reserved words previously listed. Aliases can be
created, listed, and exported with the alias command and can be removed
with the unalias command. Exported aliases remain in effect for scripts
invoked by name, but must be reinitialized for separate invocations of the
shell. (See Invocation.)
Aliasing is performed when scripts are read, not while they are executed.
Therefore, for an alias to take effect, the alias definition command has to
be executed before the command that references the alias is read.
Aliases are frequently used as shorthand for full pathnames. An option to
the aliasing facility allows the value of the alias to be automatically set
to the full pathname of the corresponding command. These aliases are
called tracked aliases.
The value of a tracked alias is defined the first time the corresponding
command is looked up and becomes undefined each time the PATH environment
variable is reset. These aliases remain tracked so that the next subse-
quent reference will redefine the value. Several tracked aliases are com-
piled into the shell. The -h flag of the set command makes each referenced
command name into a tracked alias.
The following exported aliases are compiled into the shell, but can be
unset or redefined:
autoload='typeset -fu'
false='let 0'
functions='typeset -f'
hash='alias -t'
history='fc -l'
integer='typeset -i'
nohup='nohup '
r='fc -e -'
true=':'
type='whence -v'
Tilde Substitution
After alias substitution is performed, each word is checked to see if it
begins with an unquoted ~ (tilde). If it does, then the word up to a /
(slash) is checked to see if it matches a username in the /etc/passwd file.
If a match is found, the tilde and the matched login name are replaced by
the login directory of the matched user. This is called a tilde substitu-
tion. If no match is found, the original text is left unchanged. A tilde
by itself, or in front of a /, is replaced by the value of the HOME parame-
ter. A tilde followed by a + (plus sign) or - (dash) is replaced by $PWD
and $OLDPWD, respectively.
In addition, tilde substitution is attempted when the value of a variable
assignment parameter begins with a tilde.
Command Substitution
The standard output from a command enclosed in parentheses preceded by a
dollar sign $( ) or a pair of `` (grave accents) can be used as part or all
of a word; trailing newlines are removed. In the second (archaic) form,
the string between the grave accents is processed for special quoting char-
acters before the command is executed. (See Quoting.) The command substi-
tution $(cat file) can be replaced by the equivalent but faster $(<file).
Command substitution of most special commands that do not perform
input/output redirection are carried out without creating a separate pro-
cess. An arithmetic expression enclosed in double parentheses preceded by
a dollar sign ( $(( )) ) is replaced by the value of the arithmetic expres-
sion within the double parentheses.
Parameter Substitution
A parameter is an identifier, one or more digits, or any of the characters
*, @, #, ?, -, $, and !. A named parameter (a parameter denoted by an
identifier) has a value and 0 (zero) or more attributes. Named parameters
can be assigned values and attributes by using the typeset special command.
The attributes supported by the shell are described later with the typeset
special command. Exported parameters pass values and attributes to the
environment.
The shell supports a 1-dimensional array facility. An element of an array
parameter is referenced by a subscript. A subscript is denoted by an
arithmetic expression enclosed with [ ] (brackets). To assign values to an
array, use set -A name value ... The value of all subscripts must be in
the range of 0 to 1023. Arrays need not be declared. Any reference to a
named parameter with a valid subscript is legal and an array is created if
necessary. Referencing an array without a subscript is equivalent to
referencing the element 0 (zero).
The value of a named parameter can be assigned by the following:
name=value [ name=value ]
If the integer attribute, -i, is set for name, the value is subject to
arithmetic evaluation, as described later. Positional parameters, which
are denoted by a number, can be assigned values with the set special com-
mand. Parameter $0 is set from argument 0 (zero) when the shell is
invoked. The $ (dollar sign) character is used to introduce substitutable
parameters.
${parameter}
Reads all the characters from the ${ (dollar sign left brace) to the
matching } (right brace) as part of the same word even if it contains
braces or metacharacters. The value, if any, of the parameter is sub-
stituted. The braces are required when parameter is followed by a
letter, digit, or underscore that is not to be interpreted as part of
its name or when a named parameter is subscripted. If parameter is one
or more digits, it is a positional parameter. A positional parameter
of more than one digit must be enclosed in braces. If parameter is *
(asterisk) or @ (at sign), all the positional parameters, starting with
$1, are substituted (separated by a field separator character). If an
array identifier with subscript * or @ is used, the value for each of
the elements is substituted (separated by a field separator character).
${#parameter}
Substitutes the number of positional parameters if parameter is * or @;
otherwise, the length of the value of the parameter is substituted.
${#identifier[*]}
Substitutes the number of elements in the array identifier.
${parameter:-word}
Substitutes the value of parameter if it is set and non-null; other-
wise, substitute word.
${parameter:=word}
Sets parameter to word if it is not set or is null; the value of the
parameter is then substituted. Positional parameters cannot be
assigned values in this way.
${parameter:?[word]}
Substitutes the value of parameter if it is set and is non-null; other-
wise, print word and exit from the shell. If word is omitted, a stan-
dard message is printed.
${parameter:+word}
Substitute word if parameter is set and is non-null; otherwise, substi-
tute nothing.
${parameter#pattern} | ${parameter##pattern}
Causes the value of this substitution to be the value of parameter with
the matched portion deleted if the shell pattern matches the beginning
of the value of parameter; otherwise the value of parameter is substi-
tuted. In the first form, the smallest matching pattern is deleted and
in the second form, the largest matching pattern is deleted.
${parameter%pattern} | ${parameter%%pattern}
Causes the value of this substitution to be the value of parameter with
the matched part deleted if the shell pattern matches the end of the
value of parameter; otherwise, substitute the value of parameter. In
the first form, the smallest matching pattern is deleted and in the
second form, the largest matching pattern is deleted.
If the : (colon) is omitted from the previous expressions, then the shell
checks only whether parameter is set or not.
In the previous expressions, word is not evaluated unless it is to be used
as the substituted string, so that, in the following example, pwd is exe-
cuted only if d is not set or is null:
echo ${d:-$(pwd)}
The following parameters are automatically set by the shell:
# (hash mark)
The number of positional parameters in decimal.
- (dash)
Flags supplied to the shell on invocation or by the set command.
? (question mark)
The decimal value returned by the last executed command.
$ (dollar sign)
The process number of this shell.
MAIL file when checking
for mail.
! (exclamation point)
The process number of the last background command invoked.
ERRNO
The value of errno as set by the most recently failed system call.
This value is system dependent and is intended for debugging purposes.
LINENO
The line number of the current line within the script or function being
executed.
OLDPWD
The previous working directory set by the cd command.
OPTARG
The value of the last option argument processed by the getopts special
command.
OPTIND
The index of the last option argument processed by the getopts special
command.
PPID
The process number of the parent of the shell.
PWD The present working directory set by the cd command.
RANDOM
Each time this parameter is referenced, a random integer, uniformly
distributed between 0 and 32767, is generated. The sequence of random
numbers can be initialized by assigning a numeric value to RANDOM.
REPLY
This parameter is set by the select statement and by the read special
command when no arguments are supplied.
SECONDS
Each time this parameter is referenced, the number of seconds since
shell invocation is returned. If this parameter is assigned a value,
then the value returned upon reference is the value that was assigned
plus the number of seconds since the assignment.
The following parameters are used by the shell:
CDPATH
The search path for the cd command.
COLUMNS
If this variable is set, the value is used to define the width of the
edit window for the shell edit modes and for printing select lists.
EDITOR
If the value of this variable ends in emacs, gmacs, or vi and the
VISUAL variable is not set, then the corresponding option (see set
under Special ksh Commands) is turned on.
ENV If this parameter is set, then parameter substitution is performed on
the value to generate the pathname of the script that is executed when
the shell is invoked. (See Invocation.) This file is typically used
for alias and function definitions.
FCEDIT
The default editor name for the fc command.
FPATH
The search path for function definitions. This path is searched when a
function with the -u attribute is referenced and when a command is not
found. If an executable file is found, then it is read and executed in
the current environment.
IFS Internal field separators, normally spaces, tabs, and newlines that are
used to separate command words which result from command or parameter
substitution and for separating words with the read special command.
The first character of the IFS parameter is used to separate arguments
for the $* substitution. (See Quoting.)
HISTFILE
If this parameter is set when the shell is invoked, then the value is
the pathname of the file that is used to store the command history.
(See Command Reentry.)
HISTSIZE
If this parameter is set when the shell is invoked, the number of
previously entered commands that are accessible by this shell is
greater than or equal to this number. The default is 128.
HOME
The default argument (home directory) for the cd command.
LANG
Specifies the locale of your system, which is comprised of three parts:
language, territory, and codeset. The default locale is the C locale,
which specifies the value English for language, U.S. for territory, and
ASCII for codeset. The locale specified for the LANG variable controls
the language applied to messages. Unless set explicitly, the
LC_COLLATE, LC_CTYPE, LC_MESSAGES, LC_MONETARY, LC_NUMERIC, and LC_TIME
variables also derive their settings from the locale set for LANG.
LC_COLLATE
Specifies the collating sequence to use when sorting names and when
character ranges occur in patterns. The default value is the collating
sequence for American English. If absent, the collating sequence can
be taken from the LANG parameter. If both LC_COLLATE and LANG are
absent, the ANSI C collating sequence is used.
LC_CTYPE
Specifies the character classification information to use on your sys-
tem. The default value is American English.
LC_MESSAGES
Specifies the language that the system expects for user input of yes
and no strings. The default value is American English.
LC_MONETARY
Specifies the monetary format for your system. The default value is
the monetary format for American English.
LC_NUMERIC
Specifies the numeric format for your system. The default value is the
numeric format for American English.
LC_TIME
Specifies the date and time format for your system. The default value
is the date and time format for American English.
LINES
If this variable is set, the value is used to determine the column
length for printing select lists. Select lists will print vertically
until about two-thirds of LINES lines are filled.
LOGNAME
The name of the user's login account corresponding to the login name in
the user database.
MAIL
If this parameter is set to the name of a mail file and the MAILPATH
parameter is not set, the shell informs you of the arrival of mail in
the specified file.
MAILCHECK
This variable specifies how often (in seconds) the shell checks for
changes in the modification time of any of the files specified by the
MAILPATH or MAIL parameters. The default value is 600 seconds. When
the time has elapsed, the shell checks before issuing the next prompt.
MAILPATH
A list of filenames separated by : (colons). If this parameter is set,
the shell informs you of any modifications to the specified files that
have occurred within the last MAILCHECK seconds. Each filename can be
followed by a ? (question mark) and a message that is printed. The
message will undergo parameter substitution with the parameter, $_
defined as the name of the file that has changed. The default message
is you have mail in $_.
NLSPATH
Specifies a list of directories to search to find message catalogs.
PATH
The search path for commands. (See Execution.) You cannot change PATH
if executing under rsh, except in .profile.
PS1 The value of this parameter is expanded for parameter substitution to
define the primary prompt string which by default is the $ (dollar
sign). The ! (exclamation point) in the primary prompt string is
replaced by the command number. (See Command Reentry.)
PS2 Secondary prompt string, by default > (right angle bracket).
PS3 Selection prompt string used within a select loop, by default #?
(number sign, question mark).
PS4 The value of this parameter is expanded for parameter substitution and
precedes each line of an execution trace. If omitted, the execution
trace prompt is + (plus sign).
SHELL
The pathname of the shell is kept in the environment.
TMOUT
If set to a value greater than 0 (zero), the shell terminates if a com-
mand is not entered within the prescribed number of seconds after issu-
ing the PS1 prompt. (Note that the shell can be compiled with a max-
imum bound for this value that cannot be exceeded.)
VISUAL
If the value of this variable ends in emacs, gmacs, or vi, the
corresponding option (see the set command in Special ksh Commands) is
turned on.
The shell gives default values to PATH, PS1, PS2, MAILCHECK, TMOUT, and
IFS, while HOME, SHELL, ENV, and MAIL are not set by the shell (although
HOME is set by the login command). On some systems, MAIL and SHELL are
also set by the login command.
Interpretation of Spaces
After parameter and command substitution, the results of substitutions are
scanned for the field separator characters (those found in IFS), and split
into distinct arguments where such characters are found. Explicit null
arguments (`` or '') are retained. Implicit null arguments (those result-
ing from parameters that have no values) are removed.
Filename Generation
Following substitution, each command word is scanned for the characters *
(asterisk), ? (question mark), and [ ] (brackets), unless the -f option was
set. If one of these characters appears, the word is regarded as a pat-
tern. The word is replaced with lexicographically sorted filenames that
match the pattern. If no filename is found that matches the pattern, the
word is left unchanged. When a pattern is used for filename generation,
the . (dot) character at the start of a filename or immediately following a
/ (slash), as well as the / character itself, must be matched explicitly.
In other instances of pattern matching, the / and . are not treated spe-
cially.
* Matches any string, including the null string.
? Matches any single character.
[...]
Matches any one of the enclosed characters. In an expression such as
[a-z], the - (dash) means "through" according to the current collating
sequence. The collating sequence is determined by the value of the
LC_COLLATE environment variable. If the first character following the
[ (left bracket) is a ! (exclamation point), then any character not
enclosed is matched. A - can be included in the character set by put-
ting it as the first or last character.
A pattern_list is a list of one or more patterns separated from each other
with a | (vertical bar). Composite patterns can be formed with one or more
of the following:
?(pattern_list)
Optionally matches any one of the given patterns.
*(pattern_list)
Matches zero or more occurrences of the given patterns.
+(pattern_list)
Matches one or more occurrences of the given patterns.
@(pattern_list)
Matches exactly one of the given patterns.
!(pattern_list)
Matches anything, except one of the given patterns.
Character Classes
You can use the following notation to match filenames within a range indi-
cation:
[:charclass:]
This format instructs the system to match any single character belonging to
charclass; the defined classes correspond to ctype() subroutines as fol-
lows:
alnum
alpha
cntrl
digit
graph
lower
print
punct
space
upper
xdigit
Your locale might define additional character properties, such as the fol-
lowing:
[:vowel:]
The preceding character class could be TRUE for a, e, i, o, u, or y. You
could then use [:vowel] inside a set construction to match any vowel.
Refer to The LC_CTYPE Category section of the locale file format reference
page for more information.
Quoting
The following characters have a special meaning to the shell and cause ter-
mination of a word unless quoted:
; & ( ) | ^ < >
Each of the metacharacters previously listed has a special meaning to the
shell and causes termination of a word unless quoted. A character can be
quoted (that is, made to stand for itself) by preceding it with a \
(backslash). The pair \newline is ignored. All characters enclosed
between a pair of '' (single quotes) are quoted. A single quote cannot
appear within single quotes.
Inside "" (double quotes) parameter and command substitution occurs and \
quotes the characters \, `, ', and $. The meaning of $* and $@ is identi-
cal when not quoted or when used as a parameter assignment value or as a
filename. However, when used as a command argument, '$*' is equivalent to
'$1d$2d. . .', where d is the first character of the IFS parameter, whereas
'$@' is equivalent to '$1' '$2' . . . Inside `` (grave accents) \
(backslash) quotes the characters \, `, and $. If the grave accents occur
within double quotes, then \ also quotes the ' (single quote) character.
The special meaning of reserved words or aliases can be removed by quoting
any character of the reserved word. The recognition of function names or
special command names listed later cannot be altered by quoting them.
Arithmetic Evaluation
An ability to perform integer arithmetic is provided with the let special
command. Evaluations are performed using long arithmetic. Constants are
of the form [base#]n, where base is a decimal number between 2 and 36
representing the arithmetic base and n is a number in that base. If base
is omitted, then base 10 is used.
An arithmetic expression uses the same syntax, precedence, and associa-
tivity of expression as the C language. All the integral operators, other
than ++, --, ?:, and , are supported. Named parameters can be referenced
by name within an arithmetic expression without using the parameter substi-
tution syntax. When a named parameter is referenced, its value is
evaluated as an arithmetic expression.
An internal integer representation of a named parameter can be specified
with the -i option of the typeset special command. Arithmetic evaluation
is performed on the value of each assignment to a named parameter with the
-i attribute. If you do not specify an arithmetic base, the first assign-
ment to the parameter determines the arithmetic base. This base is used
when parameter substitution occurs.
Because many of the arithmetic operators require quoting, an alternative
form of the let command is provided. For any command that begins with a
((, all the characters until a matching )) are treated as a quoted expres-
sion. More precisely, ((...)) is equivalent to let "...".
Note that ((...)) is a command with a return value, whereas $((...)) is the
way to put the string representation of the value of an arithmetic expres-
sion into the command line (that is, it is like a $ variable).
Prompting
When used interactively, the shell prompts with the value of PS1 before
reading a command. If at any time a newline is typed and further input is
needed to complete a command, then the secondary prompt (that is, the value
of PS2) is issued.
Conditional Expressions
A conditional expression is used with the [[ compound command to test
attributes of files and to compare strings. Word splitting and filename
generation are not performed on the words between [[ and ]]. Each expres-
sion can be constructed from one or more of the following unary or binary
expressions:
-a file
TRUE, if file exists.
file exists and is a block-special file.
file exists and is a character-special file.
file exists and is a directory.
file exists.
file exists and is an ordinary file.
file exists and has its setgid bit set.
file exists and its group matches the effective group ID of
this process.
file exists and has its sticky bit set.
file exists and is a symbolic link.
-n string
TRUE, if length of string is nonzero.
option is on.
-O file
TRUE, if file exists and is owned by the effective user ID of this pro-
cess.
file exists and is a FIFO special file or a pipe.
file exists and is readable by current process.
file exists and has size greater than 0 (zero).
file exists and is a socket.
-t file_des
TRUE, if file descriptor number file_des is open and associated with a
terminal device.
-u file
TRUE, if file exists and has its setuid bit set.
file exists and is writable by current process.
-z string
TRUE, if length of string is 0 (zero).
file1 -nt file2
TRUE, if file1 exists and is newer than file2.
file1 -ot file2
TRUE, if file1 exists and is older than file2.
file1 -ef file2
TRUE, if file1 and file2 exist and refer to the same file.
string = pattern
TRUE, if string matches pattern.
string != pattern
TRUE, if string does not match pattern.
string1 < string2
TRUE, if string1 collates before string2.
string1 > string2
TRUE, if string1 collates after string2.
expression1 -eq expression2
TRUE, if expression1 is equal to expression2.
expression1 is not equal to expression2.
expression1 -lt expression2
expression1 -gt expression2
TRUE, if expression1 is greater than expression2.
expression1 -le expression2
TRUE, if expression1 is less than or equal to expression2.
expression1 -ge expression2
TRUE, if expression1 is greater than or equal to expression2.
A compound expression can be constructed from these primitives by using any
of the following, listed in decreasing order of precedence.
(expression)
TRUE, if expression is TRUE. Used to group expressions.
expression is FALSE.
expression1 && expression2
TRUE, if expression1 and expression2 are both TRUE.
expression1 || expression2
TRUE, if either expression1 or expression2 is TRUE.
Input/Output
Before a command is executed, you can redirect its input and output by
using a special notation interpreted by the shell. The following can
appear anywhere in a simple command or can precede or follow a command and
are not passed on to the invoked command. Command and parameter substitu-
tion occurs before word or digit is used, except as noted in the following
text. Filename generation occurs only if the pattern matches a single file
and interpretation of spaces is not performed.
<word
Use file word as standard input (file descriptor 0).
>word
Use file word as standard output (file descriptor 1). If the file does
not exist, it is created. If the file exists, and the noclobber option
is on, this causes an error; otherwise, it is truncated to 0 (zero)
length.
>|word
Sames as >, except that it overrides the noclobber option.
>>word
Use file word as standard output. If the file exists, output is
appended to it (by first seeking to the End-of-File); otherwise, the
file is created.
<>word
Open file word for reading and writing as standard input.
word, or to an
End-of-File. No parameter substitution, command substitution, or
filename generation is performed on word. The resulting document,
called a here document, becomes the standard input. If any character
of word is quoted, then no interpretation is placed upon the characters
of the document; otherwise, parameter and command substitution occurs,
\newline is ignored, and \ must be used to quote the characters \, $,
`, and the first character of word. If - is appended to <<, then all
leading tabs are stripped from word and from the document.
<&digit
The standard input is duplicated from file descriptor digit (see
dup()). The standard output is duplicated using >& digit.
<&- The standard input is closed. The standard output is closed using >&-.
<&p The input from the coprocess (or background process) is moved to stan-
dard input.
>&p The output to the coprocess is moved to standard output.
If one of the preceding redirections is preceded by a digit, then the file
descriptor number referred to is that specified by the digit (instead of
the default 0 or 1). For example:
... 2>&1
means file descriptor 2 is to be opened for writing as a duplicate of file
descriptor 1.
The order in which redirections are specified is significant. The shell
evaluates each redirection in terms of the (file descriptor, file)
association at the time of evaluation. For example:
... 1>fname 2>&1
first associates file descriptor 1 with file fname. It then associates
file descriptor 2 with the file associated with file descriptor 1 (that is,
fname). If the order of redirections were reversed, file descriptor 2 is
associated with the terminal (assuming file descriptor 1 is) and then file
descriptor 1 is associated with file fname.
If a command is followed by & and job control is not active, the default
standard input for the command is the empty /dev/null file. Otherwise, the
environment for the execution of a command contains the file descriptors of
the invoking shell as modified by input/output specifications.
Environment
The environment is a list of name-value pairs that is passed to an executed
program in the same way as a normal argument list. The names must be iden-
tifiers and the values are character strings. The shell interacts with the
environment in several ways. On invocation, the shell scans the environ-
ment and creates a parameter for each name found, giving it the correspond-
ing value and marking it export. Executed commands inherit the environ-
ment. If you modify the values of these parameters or create new ones,
using the export or typeset -x commands, they become part of the environ-
ment. The environment seen by any executed command is thus composed of any
name-value pairs originally inherited by the shell, whose values can be
modified by the current shell, plus any additions that must be noted in the
export or typeset -x commands.
When the value of an exported parameter is changed, the shell automatically
exports the new value to all child processes. This behavior is different
from that of the Bourne shell, sh(1), which does not automatically re-
export a changed parameter.
You can augment the environment for any simple command or function by pre-
fixing it with one or more parameter assignments. A parameter assignment
argument is a word of the form identifier=value.
Thus, the following two expressions are equivalent (as far as the execution
of command is concerned):
TERM=450 command argument ...
(export TERM; TERM=450; command argument ...)
If the -k flag is set, all parameter assignment arguments are placed in the
environment, even if they occur after the command name. The following
first prints a=b c and then c:
echo a=b c
set -k
echo a=b c
This feature is intended for use with scripts written for early versions of
the shell; its use in new scripts is strongly discouraged. It is likely to
disappear someday.
Functions
The function reserved word is used to define shell functions. Shell func-
tions are read in and stored internally. Alias names are resolved when the
function is read. Functions are executed like commands with the arguments
passed as positional parameters. (See Execution.)
Functions execute in the same process as the caller and share all files and
the present working directory with the caller. Traps caught by the caller
are reset to their default action inside the function. A trap condition
that is not caught or ignored by the function causes the function to ter-
minate and the condition to be passed on to the caller. A trap on EXIT set
inside a function is executed after the function completes in the environ-
ment of the caller. Ordinarily, variables are shared between the calling
program and the function. However, the special command typeset used within
a function defines local variables whose scope includes the current func-
tion and all functions it calls.
The special command return is used to return from function calls. Errors
within functions return control to the caller.
Function identifiers can be listed with the -f or +f option of the typeset
special command. The text of functions is also listed with -f. Function
can be undefined with the -f option of the unset special command.
Ordinarily, functions are unset when the shell executes a shell script.
The -xf option of the typeset command allows a function to be exported to
scripts that are executed without a separate invocation of the shell.
Functions that need to be defined across separate invocations of the shell
should be specified in the ENV file with the -xf option of typeset.
Jobs
If the monitor option of the set command is turned on, an interactive shell
associates a job with each pipeline. It keeps a table of current jobs,
printed by the jobs command, and assigns them small integer numbers. When
a job is started asynchronously with &, the shell prints a line that looks
like:
[1] 1234
This line indicates that the job, which was started asynchronously, was job
number 1 and had one (top-level) process, whose process ID was 1234.
If you are running a job and want to do something else, you can enter the
Suspend key sequence (normally , which sends a SIGINT signal to the
current job. The shell then normally indicates that the job has been
stopped, and it prints another prompt. You can then manipulate the state
of this job, putting it in the background with the bg command, or run some
other commands and then eventually bring the job back into the foreground
with the foreground command fg. The job suspension takes effect immedi-
ately, and corresponds to the Interrupt key sequence in that pending output
and unread input are discarded. A special key sequence, , does not
generate a SIGINT signal until a program attempts to read it. (See the
read() system call for more information.) This key sequence can usefully
be typed ahead when you have prepared some commands for a job that you wish
to stop after it has read them.
A job being run in the background will stop if it tries to read from the
terminal. Background jobs are normally allowed to produce output, but this
can be disabled by issuing the stty tostop command. If you set this tty
option, then background jobs will stop when they try to produce output like
they do when they try to read input.
There are several ways to refer to jobs in the shell. A job can be
referred to by the process ID of any process of the job, or by one of the
following:
%job_number
The job with the given number.
%string
Any job whose command line begins with string.
%?string
%% Current job.
%+ Equivalent to %%.
%- Previous job.
This shell learns immediately whenever a process changes state. It nor-
mally informs you whenever a job becomes blocked so that no further pro-
gress is possible, but only just before it prints a prompt. This is done
so that it does not otherwise disturb your work.
When the monitor mode is on, each background job that is completed triggers
any trap set for CHLD.
When you try to leave the shell while jobs are stopped or running, you are
warned that You have stopped(running) jobs. You can use the jobs command to
see what they are. If you do this or immediately try to exit again, the
shell does not warn you a second time, and the stopped jobs are terminated.
Signals
The SIGINT and SIGQUIT signals for an invoked command are ignored if the
command is followed by & and job monitor option is not active. Otherwise,
signals have the values inherited by the shell from its parent (but see
also the trap command).
Execution
Each time a command is executed, the previous substitutions are carried
out. If the command name matches one of the special commands listed later,
it is executed within the current shell process. Next, the command name is
checked to see if it matches one of the user-defined functions. If it
does, the positional parameters are saved and then reset to the arguments
of the function call. When the function is completed or issues a return,
the positional parameter list is restored and any trap set on EXIT within
the function is executed. The value of a function is the value of the last
command executed. A function is also executed in the current shell pro-
cess. If a command name is not a special command or a user-defined func-
tion, a process is created and an attempt is made to execute the command
via exec.
The PATH shell parameter defines the search path for the directory contain-
ing the command. Alternative directory names are separated by a : (colon).
The default path is :/usr/bin: (specifying /usr/bin, and the current direc-
tory in that order). The current directory can be specified by two or more
adjacent colons, or by a colon at the beginning or end of the path list.
If the command name contains a / (slash), then the search path is not used.
Otherwise, each directory in the path is searched for an executable file.
If the file has execute permission but is not a directory or an a.out file,
it is assumed to be a file containing shell commands. A subshell is
spawned to read it. All nonexported aliases, functions, and named parame-
ters are removed in this case. If the shell command file does not have
read permission, or if the setuid and/or setgid bits are set on the file,
the shell executes an agent whose job it is to set up the permissions and
execute the shell with the shell command file passed down as an open file.
A command in parentheses is executed in a subshell without removing nonex-
ported quantities.
Command Reentry
The text of the last HISTSIZE (default 128) commands entered from a termi-
nal device is saved in a history file. The $HOME/.sh_history file is used
if the HISTFILE variable is not set or is not writable. A shell can access
the commands of all interactive shells that use the same named HISTFILE.
The fc special command is used to list or edit a portion of this file. The
portion of the file to be edited or listed can be selected by number or by
giving the first character or characters of the command. A single command
or range of commands can be specified. If you do not specify an editor
program as an argument to fc, then the value of the FCEDIT parameter is
used. If FCEDIT is not defined, then /usr/bin/ed is used. The edited com-
mands are printed and reexecuted upon leaving the editor. The editor name
- (dash) is used to skip the editing phase and to reexecute the command.
In this case, a substitution parameter of the form old=new can be used to
modify the command before execution. For example, if r is aliased to 'fc
-e -', then typing `r bad=good c' reexecutes the most recent command, which
starts with the letter c, replacing the first occurrence of the string bad
with the string good.
Inline Editing Options
Normally, each command line entered from a terminal device is simply typed
followed by a newline ( or linefeed). If the emacs, gmacs, or vi
option is active, you can edit the command line. To be in any of these
edit modes, set the corresponding option. An editing option is automati-
cally selected each time the VISUAL or EDITOR variable is assigned a value
ending in either of these option names.
The editing features require that the terminal accept as
carriage-return without linefeed and that a space must overwrite the
current character on the screen. ADM terminal users should set the space-
advance switch to Space. Hewlett-Packard series 2621 terminal users should
set the straps to bcGHxZ etX.
The editing modes create the impression that the user is looking through a
window at the current line. The window width is the value of COLUMNS if it
is defined, otherwise it is 80 bytes. If the line is longer than the win-
dow width minus 2, a mark is displayed at the end of the window to notify
the user. As the cursor moves and reaches the window boundaries, the win-
dow is centered about the cursor. The mark is a > (right angle bracket) if
the line extends on the right side of the window, a < (left angle bracket)
if the line extends on the left side of the window, and an * (asterisk) if
the line extends on both sides of the window.
The search commands in each edit mode provide access to the history file.
Only strings are matched, not patterns, although if the leading character
in the string is a ^ (circumflex), the match is restricted to begin at the
first character in the line.
The emacs Editing Mode
This mode is entered by enabling either the emacs or gmacs option. The
only difference between these two modes is the way they handle .
To edit, the user moves the cursor to the point needing correction and then
inserts or deletes characters or words as needed. All the editing commands
are control characters or escape sequences. The notation for control char-
acters is ^ (circumflex) followed by the character. For example, ^F is the
notation for . This is entered by pressing f while holding down
. is not depressed. (The notation ^? indicates .)
The notation for escape sequences is M- followed by a character. For exam-
ple, M-f (pronounced Meta f) is entered by pressing (ASCII 033) fol-
lowed by f. (M-F would be the notation for followed by (cap-
ital) F.)
All edit commands operate from any place on the line (not just at the
beginning). Do not press or linefeed after edit commands except
when noted.
or or right arrow key
Moves the cursor forward (right) one character.
Moves the cursor forward one word. (The emacs editor's definition of a
word is a string of characters, consisting of only letters, digits, and
underscores, and delimited with spaces or tabs.)
or or left arrow key
Moves the cursor backward (left) one character.
Moves the cursor backward one word.
Moves the cursor to the start of the line.
Moves the cursor to the end of the line.
character
Moves the cursor forward on the current line to the character indicated
by the character argument.
character
Moves the cursor backward on the current line to the character indi-
cated by the character argument.
Ctrl-x>
Interchanges the cursor and mark.
Erase
Deletes the previous character. (User-defined Erase character as
defined by the stty command, often or #.)
Deletes the current character.
Deletes the current word.
Deletes the previous word.
Deletes the previous word.
Deletes the previous word (if your Interrupt character is ,
this command does not work).
Transposes the current character with next character in emacs mode.
Transposes two previous characters in gmacs mode.
Capitalizes the current character.
Capitalizes the current word.
Changes the current word to lowercase.
Deletes from the cursor to the end of the line. If preceded by a
numerical parameter whose value is less than the current cursor posi-
tion, deletes from given position up to the cursor. If preceded by a
numerical parameter whose value is greater than the current cursor
position, deletes from the cursor up to given cursor position.
Deletes from the cursor to the mark.
Pushes the region from the cursor to the mark on the stack.
Kill
Kills the entire current line. If two Kill characters are entered in
succession, all Kill characters from then on cause a linefeed (useful
when using paper terminals). (User-defined Kill character as defined
by the stty command, often or @.)
Restores the last item removed from the line. (Yanks the item back to
the line.)
Performs a linefeed and prints the current line.
(Null character.) Sets the mark.
space>
Sets the mark.
Executes the current line (newline).
Executes the current line (enter).
EOF The End-of-File character is processed as an End-of-File only if the
current line is null.
Fetches the previous command. Each time is entered, the pre-
vious command back in time is accessed. Moves back one line when not
on the first line of a multiline command.
or or down arrow key
Fetches the least recent (oldest) history line.
> or or up arrow key
Fetches the most recent (youngest) history line.
Fetches the next command line. Each time is entered, the next
command line forward in time is accessed.
string
Reverses the search history for a previous command line containing
string. If an argument of 0 (zero) is given, the search is forward.
The string command is terminated by a or newline character.
If string is preceded by a ^ (circumflex), the matched line must begin
with string. If string is omitted, then the next command line contain-
ing the most recent string is accessed. In this case, an argument of 0
(zero) reverses the direction of the search.
Executes the current line and fetches the next line relative to current
line from the history file. (Operate)
digits
Defines the numeric parameter (escape). The digits are taken as an
argument to the next command. The commands that accept a parameter are
, , , , , , ,
, , , , , _>, ,
, , , , and .
letter
Your alias list is searched for an alias by the name _letter and if an
alias of this name is defined, its value is inserted on the input
queue. letter must not be one of the preceding metafunctions. (Soft-
key)
letter
Your alias list is searched for an alias by the name __letter and if an
alias of this name is defined, its value is inserted on the input queue
(Soft-key). This can be used to program functions keys on many sys-
tems.
letter
Same as letter.
The last word of the previous command is inserted on the line. If pre-
ceded by a numeric parameter, the value of this parameter determines
which word to insert, rather than the last word.
_>
Same as the combination.
Attempts filename generation on the current word. An * (asterisk) is
appended if the word does not match any file or contain any special
pattern characters.
Filename completion. Replaces the current word with the longest common
prefix of all filenames matching the current word with an asterisk
appended. If the match is unique, a / (slash) is appended if the file
is a directory, and a space is appended if the file is not a directory.
Lists the files matching current word pattern if an * (asterisk) were
appended.
Multiplies the argument of the next command by 4.
\ Escapes the next character. Editing characters, the user's Erase,
Kill, and Interrupt (normally by using ) characters can be
entered in a command line or in a search string if preceded by a \
(backslash). The backslash removes the next character's editing
features (if any).
Displays the version of the shell.
Inserts a # (number sign) at the beginning of the line and executes it.
This causes a comment to be inserted in the history file.
The vi Editing Mode
There are two typing modes. Initially, when you enter a command you are in
the input mode. To edit, the user enters control mode by typing
(ASCII 033) and moves the cursor to the place needing correction and then
inserts or deletes characters or words as needed. Most control commands
accept an optional repeat count prior to the command. When in vi mode on
most systems, canonical processing is initially enabled and the command is
echoed again if the speed is 1200 baud or greater, if it contains any con-
trol characters, or if less than 1 second has elapsed since the prompt was
printed. The Escape character terminates canonical processing for the
remainder of the command and the user can then modify the command line.
This scheme has the advantages of canonical processing with the type-ahead
echoing of raw mode. If the option viraw is also set, the terminal always
has canonical processing disabled. This mode is implicit for systems that
do not support two alternate End-of-Line delimiters, and can be helpful for
certain terminals.
Input Edit Commands
By default the editor is in input mode.
Erase
(User-defined Erase character as defined by the stty command, often
or #.) Deletes the previous character.
Deletes the previous space-separated word.
Terminates the shell.
Escapes the next character. Editing characters and the user's Erase or
Kill characters can be entered in a command line or in a search string
if preceded by a . removes the next character's edit-
ing features (if any).
\ Escapes the next Erase or Kill character.
Motion Edit Commands
These commands move the cursor:
[count]l
Cursor forward (right) one character.
[count]w
Cursor forward one word. A word is a string of characters delimited by
spaces or tabs.
[count]W
Cursor to the beginning of the next word that follows a space.
[count]e
Cursor to the end of the word.
[count]E
Cursor to end of the current space-delimited word.
[count]h
Cursor backward (left) one character.
[count]b
Cursor backward one word.
[count]B
Cursor to the preceding space-delimited word.
[count]|
Cursor to the column count.
[<
[<
[<
Equivalent to f followed by h.
[<
Equivalent to F followed by l.
[count];
Repeats count times, the last single character find command: f, F, t,
or T.
[count],
Reverses the last single character find command count times.
0 Cursor to the start of the line.
^ Cursor to the first nonspace character in the line.
$ Cursor to the end of the line.
Search Edit Commands
These commands access your command history.
[count]k
Fetches the previous command. Each time k is entered, the previous
command back in time is accessed.
[count]-
Equivalent to k.
[count]j
Fetches the next command. Each time j is entered, the next command
forward in time is accessed.
[count]+
Equivalent to j.
[count]G
Fetches the command number count. The default is the least recent his-
tory command.
/string
Searches backward through history for a previous command containing the
specified string. string is terminated by or a newline char-
acter. If the specified string is preceded by a ^ (circumflex), the
matched line must begin with string. If string is null, the previous
string is used.
?string
Same as / (slash) except that the search is in the forward direction.
n Searches for next match of the last pattern to the / or ? commands.
N Searches for next match of the last pattern to the / or ? commands, but
in reverse direction. Searches the command history for the string
entered by the previous / command.
Text Modification Edit Commands
These commands modify the line.
a Enters input mode and enters text after the current character.
A Appends text to the end of the line. Equivalent to $a.
[count]cmotion
c[count]motion
Deletes the current character through the character to which motion
would move the cursor, and enters input mode. If motion is c, the
entire line is deleted and input mode is entered.
C Deletes the current character through the end of line, and enters input
mode. Equivalent to c$.
S Equivalent to cc.
D Deletes the current character through the end of line. Equivalent to
d$.
[count]dmotion
d[count]motion
Deletes the current character through the character to which motion
would move. If motion is d, the entire line is deleted.
i Enters input mode and inserts text before the current character.
I Inserts text before the beginning of the line. Equivalent to 0i.
[count]P
Places the previous text modification before the cursor.
[count]p
Places the previous text modification after the cursor.
R Enters input mode and replaces characters on the screen with the char-
acters you type, overlay fashion.
[<
Replaces the count characters, starting at the current cursor position
[count]x
Deletes the current character.
[count]X
Deletes the preceding character.
[count].
Repeats the previous text modification command.
[count]~
Inverts the case of the count characters, starting at the current cur-
sor position and advancing the cursor.
[count]_
Causes the count word of the previous command to be appended and input
mode entered. The last word is used if count is omitted.
* Causes an * (asterisk) to be appended to the current word and filename
generation to be attempted. If no match is found, it rings the bell.
Otherwise, the word is replaced by the matching pattern and input mode
is entered.
\ Filename completion. Replaces the current word with the longest common
prefix of all filenames matching the current word with an * (asterisk)
appended. If the match is unique, a / (slash) is appended if the file
is a directory; a space is appended if the file is not a directory.
Miscellaneous vi Commands
[count]ymotion
y[count]motion
Yanks the current character through the character to which motion would
move the cursor and puts the characters into the delete buffer. The
text and cursor are unchanged.
Y Yanks from current position to the end of line. Equivalent to y$.
u Undoes the last text-modifying command.
U Undoes all the text-modifying commands performed on the line.
[count]v
Returns the command fc -e ${VISUAL:-${EDITOR:-vi}} count in the input
buffer. If count is omitted, the current line is used.
Performs a linefeed and prints the current line. Effective only in
control mode.
Executes the current line, regardless of mode (newline).
Executes the current line, regardless of mode (enter).
# Sends the line after inserting a # (number sign) in front of the line.
Useful for causing the current line to be inserted in the history
without being executed.
= Lists the filenames that match the current word if an * (asterisk) is
appended to it.
@letter
Searches the alias list for an alias by the name _letter . If an alias
of this name is defined, its value is inserted in the input queue for
processing.
Special ksh Commands
The following simple commands are executed in the shell process.
Input/output redirection is permitted. Unless otherwise indicated, the
output is written on file descriptor 1 and the exit status, when there is
no syntax error, is 0 (zero).
Commands that are indicated as command1 or command2 are treated specially
in the following ways:
++ Parameter assignment lists that precede the command remain in effect
when the command completes.
++ I/O redirections are processed after parameter assignments.
++ Errors cause a script that contains the commands so marked to abort.
++ Words, following a command specified as command2 that are in the for-
mat of a parameter assignment, are expanded with the same rules as a
parameter assignment. This means that ~ (tilde) substitution is per-
formed after the = (equal sign). Word splitting and filename genera-
tion are not performed.
:[argument ...]1
The command only expands arguments.
. file [argument ...]1
Reads the complete file and executes the commands. The commands are
executed in the current shell environment. The search path specified
by PATH is used to find the directory containing file. If any argu-
ments are specified, they become the positional parameters. Otherwise,
the positional parameters are unchanged. The exit status is the exit
status of the last command executed.
alias [-tx] [name[=value ...]]2
The alias command with no arguments prints the list of aliases in the
form name=value on standard output. An alias is defined for each name
whose value is given. A trailing space in value causes the next word
to be checked for alias substitution. The -t flag is used to set and
list tracked aliases. The value of a tracked alias is the full path-
name corresponding to the given name. The value becomes undefined when
the value of PATH is reset but the aliases remained tracked. Without
the -t flag, for each name in the argument list for which no value is
given, the name and value of the alias is printed. The -x flag is used
to set or print exported aliases. An exported alias is defined for
scripts invoked by name. The exit status is nonzero if a name is given
without a value, and no alias was defined.
bg [job ...]
Puts each specified job into the background. The current job is put
into the background if job is not specified. (See Jobs for a descrip-
tion of the format of job.)
for, while, until, or select loop, if any. If
n is specified, breaks n levels.
for, while, until, or
select loop. If n is specified, resumes at the nth enclosing loop.
cd [argument]
argument. If argument is a - (dash),
the directory is changed to the previous directory. The HOME shell
parameter is the default argument. The PWD parameter is set to the
current directory. The CDPATH shell parameter defines the search path
for the directory containing argument. Alternative directory names are
separated by a : (colon). The default path is a null string, specify-
ing the current directory. Note that the current directory is
specified by a null pathname, which can appear immediately after the =
(equal sign) or between the colon delimiters anywhere else in the path
list.
If argument begins with a / (slash), the search path is not used. Oth-
erwise, each directory in the path is searched for argument. The
second form of cd substitutes the string new for the string old in the
current directory name PWD and tries to change to this new directory.
The cd command cannot be executed by rsh.
echo [argument ...]
Writes arguments to standard output.
eval [argument ...]1
The arguments are read as input to the shell and the resulting commands
are executed.
exec [argument ...]1
If argument is given, the command specified by the arguments is exe-
cuted in place of this shell without creating a new process.
Input/output arguments can appear and affect the current process. If
no arguments are given, the effect of this command is to modify file
descriptors as prescribed by the input/output redirection list. In
this case, any file descriptor numbers greater than 2 that are opened
with this mechanism are closed when invoking another program.
n. If n is
omitted, the exit status is that of the last command executed. An
End-of-File also causes the shell to exit, except for a shell which has
the ignoreeof option (see set) turned on.
export [name[=value ...]]2
export -p
The given names are marked for automatic export to the environment of
and values of all exported variables, one per line, in the format
export variable=value
fc [-r] [-e editor] [first [last]]
fc -l [-nr] [first [last]]
fc -s [old=new] [command ]
In the first two forms, a range of commands from first to last is
selected from the last HISTSIZE commands that were entered at the ter-
minal. The arguments first and last can be specified as a number or as
a string. A string is used to locate the most recent command that
starts with the given string. A negative number is used as an offset
to the current command number.
In the first form the editor program editor is invoked on a file con-
taining these keyboard commands. In the second form, the commands are
listed on standard output and no editor is invoked.
In the first form, if editor is not supplied, the value of the parame-
ter FCEDIT (default /usr/bin/ed) is used as the editor. When editing
is complete, the edited commands are executed. If last is not speci-
fied, then it is set to first. If first is not specified, the default
is the previous command for editing and -16 for listing. The -r flag
reverses the order of the commands and the -n flag suppresses command
numbers when listing. In the third form, command is reexecuted,
without invoking the editor, after the optional substitution old=new is
performed.
fg [job ...]
Each job specified is brought to the foreground. Otherwise, the
current job is brought into the foreground. (See Jobs for a descrip-
tion of the format of job.)
getopts optstring name [argument ...]
Checks argument for legal options. If argument is omitted, the posi-
tional parameters are used. An option argument begins with a + (plus
sign) or a - (dash). An option not beginning with + or - or the argu-
ment -- ends the options. The optstring special command contains the
letters that getopts recognizes. If a letter is followed by a :
(colon), that option is expected to have an argument. The options can
be separated from the argument by spaces. The getopts special command
places the next option letter it finds inside variable name each time
it is invoked with a + prepended when argument begins with a +. The
index of the next argument is stored in OPTIND.
The option argument, if any, gets stored in OPTARG. A leading : in
optstring causes getopts to store the letter of an invalid option in
OPTARG, and to set name to a ? (question mark) for an unknown option
and to : when a required option is missing. Otherwise, getopts prints
an error message. The exit status is nonzero when there are no more
options.
hash [-r]
Without the flag, equivalent to alias -t. The -r flag empties the list
of tracked aliases.
inlib library_name
This command is no longer supported. See the loader(5) reference page
for information on using shared libraries.
jobs [-lnp] [job ...]
Lists information about each given job; or all active jobs if job is
omitted. The -l flag lists process IDs in addition to the normal
information. The -n flag only displays jobs that have stopped or
exited since last notified. The -p flag causes only the process group
to be listed. (See Jobs for a description of the format of job.)
kill [-signal] job ...
kill -l
Sends either the TERM signal or the specified signal to the specified
jobs or processes. Signals are either given by number or by names (as
given in /usr/include/signal.h, stripped of the prefix SIG). If the
signal being sent is TERM (terminate) or HUP (hangup), the job or pro-
cess is sent a CONT (continue) signal if it is stopped. The argument
job can be the process ID of a process that is not a member of one of
the active jobs. (See Jobs for a description of the format of job.) In
the second form, kill -l, the signal numbers and names are listed.
let argument ...
Each argument is a separate arithmetic expression to be evaluated.
(See Arithmetic Evaluation for a description of arithmetic expression
evaluation.) The exit status is 0 (zero) if the value of the last
expression is nonzero, and 1 otherwise.
newgrp [-] [group]
Changes the primary group identification of the current shell process
to group. If you specify a - (dash), newgrp changes the login environ-
ment to the login environment of the new group. If you do not specify
a group, newgrp changes the group identification to that specified for
the current user in the /etc/passwd file. The newgrp command recog-
nizes group names only; it does not recognize group ID numbers.
Only a user with superuser authority can change the primary group of
the shell to one to which that user does not belong.
Any active user-generated shell is terminated when the newgrp command
is used.
print [-Rnprsu[n]] [argument ...]
The shell output mechanism. With no flags or with flag - or --, the
arguments are printed on standard output as described by echo. In raw
mode, -R or -r, the escape conventions of echo are ignored. The -R
option prints all subsequent arguments and options other than -n.
The -p option causes the arguments to be written onto the pipe of the
process spawned with |& instead of standard output. The -s option
causes the arguments to be written onto the history file instead of
standard output. The -u flag can be used to specify a 1-digit file
1. If the -n flag is used, no newline is added to the output.
pwd Equivalent to print -r - $PWD.
read [-prsu[n]] [name?prompt] [name ...]
The shell input mechanism. One line is read and is broken up into
fields using the characters in IFS as separators. In raw mode, a \
(backslash) at the end of a line does not signify line continuation.
The first field is assigned to the first name, the second field to the
second name, and so on, with leftover fields assigned to the last name.
The -p flag causes the input line to be taken from the input pipe of a
process spawned by the shell using |&. If the -s flag is present, the
input is saved as a command in the history file. The -u flag can be
used to specify a 1-digit file descriptor unit to read from. The file
descriptor can be opened with the exec special command. The default
value of n is 0 (zero). If name is omitted, REPLY is used as the
default name. The exit status is 0 (zero) unless an End-of-File is
encountered. An End-of-File with the -p flag causes cleanup for this
process so that another can be spawned. If the first argument contains
a ? (question mark), the remainder of this word is used as a prompt on
standard error when the shell is interactive. The exit status is 0
(zero) unless an End-of-File is encountered.
readonly [name[=value ...]]2
readonly -p
The variables whose names are given are marked read-only. These vari-
ables can not be unset or changed by subsequent assignment. The -p flag
outputs the names and values of all readonly variables, one per line,
in the format
readonly variable=value
n. If n is omitted, the return status is
that of the last command executed. If return is invoked while not in a
function or a . (dot) script, it is the same as an exit.
rmlib library_name
This command is no longer supported. See the loader(5) reference page
for information on using shared libraries.
set [+ | -abCefhkmnopstuvx] [+ | -o option ...] \
[+ | -A name] [argument ...]
Using + rather than - causes these flags to be turned off. These flags
can also be used upon invocation of the shell. The flags for the set
command have the following meanings:
-A name
Array assignment. Unsets the variable name and assign values
sequentially from the list argument. If +A is used, the variable
name is not unset first.
-a Automatically exports subsequent parameters that are defined.
-b Causes the shell to notify the user asynchronously of background
job completions.
-C Prevent existing files from being overwritten by the shell's >
redirection operator; the >| redirection operator overrides this
noclobber option for an individual file.
-e If a command has a nonzero exit status, executes the ERR trap, if
set, and exits. This mode is disabled while reading profiles.
-f Disables filename generation.
-h Each command becomes a tracked alias when first encountered.
-k All parameter assignment arguments are placed in the environment
for a command, not just those that precede the command name.
-m Background jobs will run in a separate process group and a line
will print upon completion. The exit status of background jobs is
reported in a completion message. On systems with job control,
this flag is turned on automatically for interactive shells.
-n Reads commands and checks them for syntax errors, but does not exe-
cute them. Ignored for interactive shells.
-o The argument can be one of the following option names:
allexport
Same as a.
errexit
Same as e.
bgnice
Runs all background jobs at a lower priority. This is the
default mode.
emacs
Invokes an emacs style inline editor for command entry.
gmacs
Invokes a gmacs-style inline editor for command entry.
ignoreeof
The shell does not exit on End-of-File. The exit command must
be used.
keyword
Same as k.
markdirs
All directory names resulting from filename generation have a
trailing / (slash) appended.
monitor
Same as m.
noclobber
Prevents redirection > from truncating existing files.
Requires >| to truncate a file when turned on.
noexec
Same as n.
noglob
Same as f.
nolog
Does not save function definitions in history file.
nounset
Same as u.
privileged
Same as p.
verbose
Same as v.
trackall
Same as h.
vi Invokes, in insert mode, a vi-style inline editor until you
press Escape (ASCII 033). This changes to move mode. A return
sends the line.
viraw
Each character is processed as it is entered in vi mode.
xtrace
Same as x.
If no option name is supplied, then the current option settings
are printed.
-p Disables processing of the $HOME/.profile file and uses the
/etc/suid_profile file instead of the ENV file. This mode is on
whenever the effective user ID or group ID is not equal to the real
user ID or group ID. Turning this off causes the effective user ID
and group ID to be set to the real user ID and group ID.
-s Sorts the positional parameters.
-t Exits after reading and executing one command.
-u Treats unset parameters as an error when substituting.
-v Prints shell input lines as they are read.
-x Prints commands and their arguments as they are executed.
- Unsets x and v flags and stops examining arguments for flags.
-- Does not change any of the flags; useful in setting $1 to a value
beginning with -. If no arguments follow this flag, the positional
parameters are unset.
These flags can also be used upon invocation of the shell. The
current set of flags can be found in $-. Unless -A is specified,
the remaining arguments are positional parameters and are assigned,
in order, to $1 $2 .... If no arguments are given, the names and
values of all named parameters are printed on the standard output.
If the only argument is +, the names of all named parameters are
printed.
$n+1 ... are renamed $1 ...; the
default n is 1. The argument n can be any arithmetic expression that
evaluates to a nonnegative number less than or equal to $#.
times1
Prints the accumulated user and system times for the shell and for
processes run from the shell.
trap [argument] [signal ...]1
The argument variable specifies a command to be read and executed when
the shell receives the specified signals. (Note that argument is
scanned once when the trap is set and once when the trap is taken.)
Each signal can be given as a number or as the name of the signal.
Trap commands are executed in order of signal number. Any attempt to
set a trap on a signal that was ignored on entry to the current shell
is ineffective.
If argument is omitted or is -, all traps signal are reset to their
original values. If argument is the null string, this signal is
ignored by the shell and by the commands it invokes. If signal is ERR,
argument is executed whenever a command has a nonzero exit status. If
signal is DEBUG, argument is executed after each command. If signal is
0 or EXIT and the trap statement is executed inside the body of a func-
tion, the command argument is executed after the function completes.
If signal is 0 (zero) or EXIT for a trap set outside any function, the
command argument is executed on exit from the shell. The trap command
with no arguments prints a list of commands associated with each signal
number.
typeset [+ | -HLRZfilrtux[n]] [name[=value ...]]2
Sets attributes and values for shell parameters. When invoked inside a
function, a new instance of the parameter name is created. The parame-
ter value and type are restored when the function completes. The fol-
lowing list of attributes can be specified:
-f The names refer to function names rather than parameter names. No
assignments can be made and the only other valid flags are -t, -u,
and -x. The -t flag turns on execution tracing for this function.
The -u flag causes this function to be marked undefined. The FPATH
variable is searched to find the function definition when the func-
tion is referenced. The -x flag allows the function definition to
remain in effect across shell procedures invoked by name.
-H Provides system-to-hostname file mapping on machines that restrict
the set of characters in filenames.
nonzero, it defines the output arithmetic base; otherwise, the
first assignment determines the output base.
-l All uppercase characters are converted to lowercase. The uppercase
-u flag is turned off.
nonzero, it defines the width of the field; otherwise, it is deter-
mined by the width of the value of first assignment. When the
parameter is assigned, it is filled on the right with spaces or
truncated, if necessary, to fit into the field. Leading zeros are
removed if the -Z flag is also set. The -R flag is turned off.
-r The given names are marked read-only and these names cannot be
changed by subsequent assignment.
defines the width of the field; otherwise, it is determined by the
width of the value of first assignment. The field is left-filled
with spaces or truncated from the end if the parameter is reas-
signed. The L flag is turned off.
-t Tags the named parameters. Tags are user definable and have no
special meaning to the shell.
-u All lowercase characters are converted to uppercase characters.
The lowercase -l flag is turned off.
-x The given names are marked for export.
-Z Right justifies and fills with leading zeros if the first nonspace
c
it defines the width of the field; otherwise, it is determined by
the width of the value of first assignment.
Using + (plus sign) rather than - (dash) causes these flags to be
turned off. If no name arguments are given but flags are specified, a
list of names (and optionally the values) of the parameters that have
these flags set is printed. (Using + rather than - keeps the values
from being printed.) If no names and flags are given, the names and
attributes of all parameters are printed.
ulimit [-HSacdfmnstvw] [limit]
Sets or displays a resource limit. Available resources limits follow.
Many systems do not contain one or more of these limits. The limit for
a specified resource is set when limit is specified. The value of
limit can be a number in the unit specified with each resource, or the
value unlimited.
The H and S flags specify whether the hard limit or the soft limit for
the given resource is set. A hard limit cannot be increased once it is
set. A soft limit can be increased up to the value of the hard limit.
If neither H nor S is specified, the limit applies to both. The
current resource limit is printed when limit is omitted. In this case,
the soft limit is printed unless H is specified. When more than one
resource is specified, the limit name and unit are printed before the
value.
-a Lists all of the current resource limits.
-c The number of 512-byte blocks on the size of core dumps.
-d The number of Kilobytes on the size of the data area.
-f The number of 512-byte blocks on files written by child processes
(files of any size can be read).
-m The number of Kilobytes on the size of physical memory.
-n The number of file descriptors.
-s The number of Kilobytes on the size of the stack area.
-t The number of seconds to be used by each process.
-v The number of Kilobytes for virtual memory. Note: This option is
supported only if RLIMIT_VMEM has been defined in
/usr/include/sys/resource.h.
-w The number of Kilobytes for the swap area. Note: This option is
supported only if RLIMIT_SWAP has been defined in
/usr/include/sys/resource.h.
If no option is given, -f is assumed.
umask [-S] [mask]
The user file-creation mask is set to mask (See umask.) mask can
either be an octal number or a symbolic value as described in chmod.
If a symbolic value is given, the new umask value is the complement of
the result of applying mask to the complement of the previous umask
value. If mask is omitted, the current value of the mask is printed.
-S Produces Symbolic output
unalias name ...
unalias -a
The parameters given by the list of names are removed from the alias
list. The unalias -a command removes all aliases from the current
shell execution environment.
unset [-fv] name ...
The variables or functions given by the list of names are unassigned,
that is, their values and attributes are erased. Read-only variables
cannot be unset. If the -f flag is specified, the names refer to func-
tion names. If no flags or the -v flag is specified, the names refer
to variables. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND, RAN-
are subsequently assigned.
wait [job]
Waits for the specified job and reports its termination status. If job
is not given, all currently active child processes are waited for. The
exit status from this command is that of the process waited for. (See
Jobs for a description of the format of job.)
whence [-pv] name ...
For each name, indicates how it would be interpreted if used as a com-
mand name. The -v flag produces a more verbose report. The -p flag
does a path search for name even if name is an alias, a function, or a
reserved word.
Invocation
If the shell is invoked by exec, and the first character of argument zero
($0) is - (dash), the shell is assumed to be a login shell and commands are
read from /etc/profile and then from either .profile in the current direc-
tory or $HOME/.profile, if either file exists. Next, commands are read
from the file named by performing parameter substitution on the value of
the ENV environment variable, if the file exists. If the -s flag is not
present and argument is present, a path search is performed on the first
argument to determine the name of the script to execute. The script argu-
ment must have read permission and any setuid and getgid settings are
ignored. Commands are then read, as described in the following text.
See the FLAGS section for a complete description of flags that can be
interpreted by the shell when it is invoked.
FLAGS
-c command_string
Causes ksh to read commands from command_string.
-i Causes ksh to run as an interactive shell. The SIGTERM signal is thus
ignored, and the SIGINT signal is caught, causing the current command
to be terminated and a new prompt to be output.
-r Causes ksh to run as a restricted shell.
-s Causes ksh to read commands from standard input. If you do not specify
the -c flag or do not specify any arguments to ksh other than flags,
ksh automatically invokes the -s flag. The -c flag overrides the -s
flag, however.
The rest of the flags that can be used with ksh are described under the set
subcommand in the subsection Special ksh Commands.
NOTES
1. If a command is executed, and a command with the same name is
installed in a directory in the search path before the directory where
the original command was found, the shell will execute the original
command. Use the hash command to correct this situation.
2. When the shell encounters the >> characters, it does not open the file
in append mode; instead, the shell opens the file for writing and
seeks to the end.
3. Failure (nonzero exit status) of a special command preceding a || sym-
bol prevents the list following || from executing.
4. If a command that is a tracked alias is executed, and then a command
with the same name is installed in a directory in the search path
before the directory where the original command was found, the shell
continues to exec the original command. Use the -t flag of the alias
command to correct this situation.
5. Using the fc built-in command within a compound command causes the
whole command to disappear from the history file.
6. The built-in .file command reads the whole file before any commands
are executed. Therefore, the alias and unalias commands in the file
do not apply to any functions defined in the file.
7. Traps are not processed while a job is waiting for a foreground pro-
cess. Thus, a trap on CHLD is not executed until the foreground job
terminates.
RETURN VALUES
Errors detected by the shell, such as syntax errors, cause the shell to
return a nonzero exit status. Otherwise, the shell returns the exit status
of the last command executed. (See also the exit command, described previ-
ously.) If the shell is being used noninteractively, execution of the
shell file is abandoned. Run-time errors detected by the shell are
reported by printing the command or function name and the error condition.
If the line number that the error occurred on is greater than 1, the line
number is also printed in [ ] (brackets) after the command or function
name.
FILES
/etc/profile
System profile.
$HOME/.profile
User profile.
/etc/passwd
Contains user information.
RELATED INFORMATION
Commands: cat(1), cd(1), chmod(1), csh(1), echo(1), env(1)/printenv(1),
sh(1), stty(1), test(1), vi(1)/vedit(1)/view(1).
Functions: exec(2), fcntl(2), fork(2), ioctl(2), lseek(2), pipe(2), sigac-
tion(2), umask(2), wait(2).
Routines: rand(3), ulimit(3).
Files: null(7).
Miscellaneous: loader(5)
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