set(1) User Commands set(1)NAME
set, unset, setenv, unsetenv, export - shell built-in functions to
determine the characteristics for environmental variables of the cur‐
rent shell and its descendents
SYNOPSIS
sh
set [--aefhkntuvx [argument]]...
unset [name]...
export [name]...
csh
set [var [= value]]
set var [n] = word
unset pattern
setenv [VAR [word]]
unsetenv variable
ksh
set [±abCefhkmnopstuvx] [±o option]... [±A name]
[arg]...
unset [-f] name...
**export [name [=value]]...
**export [-p]
ksh93
+set [±abCefGhkmnoprstuvx] [±o option]... [±A vname]
[arg]...
+unset [-fnv] vname...
++export [-p] [name[=value]]...
DESCRIPTION
sh
The set built-in command has the following options:
-- Does not change any of the flags. This option is useful in set‐
ting $1 to −.
-a Marks variables which are modified or created for export.
-e Exits immediately if a command exits with a non-zero exit status.
-f Disables file name generation.
-h Locates and remembers function commands as functions are defined.
Function commands are normally located when the function is exe‐
cuted.
-k All keyword arguments are placed in the environment for a com‐
mand, not just those that precede the command name.
-n Reads commands but does not execute them.
-t Exits after reading and executing one command.
-u Treats unset variables as an error when substituting.
-v Prints shell input lines as they are read.
-x Prints commands and their arguments as they are executed.
Using + rather than − causes these flags to be turned off. These flags
can also be used upon invocation of the shell. The current set of flags
can be found in $−. The remaining arguments are positional parameters
and are assigned, in order, to $1, $2, .... If no arguments are speci‐
fied the values of all names are printed.
For each name, unset removes the corresponding variable or function
value. The variables PATH, PS1, PS2, MAILCHECK, and IF cannot be unset.
With the export built-in, the specified names are marked for automatic
export to the environment of subsequently executed commands. If no
arguments are specified, variable names that have been marked for
export during the current shell's execution are listed. Function names
are not exported.
csh
With no arguments, set displays the values of all shell variables. Mul‐
tiword values are displayed as a parenthesized list. With the var argu‐
ment alone, set assigns an empty (null) value to the variable var. With
arguments of the form var = value set assigns value to var, where value
is one of:
word A single word (or quoted string).
(wordlist) A space-separated list of words enclosed in parentheses.
Values are command and filename expanded before being assigned. The
form set var[n]=word replaces the n'th word in a multiword value with
word.
unset removes variables whose names match (filename substitution) pat‐
tern. All variables are removed by `unset *'.
With no arguments, setenv displays all environment variables. With the
VAR argument, setenv sets the environment variable VAR to an empty
(null) value. (By convention, environment variables are normally speci‐
fied upper-case names.) With both VAR and word arguments specified,
setenv sets VAR to word, which must be either a single word or a quoted
string. The PATH variable can take multiple word arguments, separated
by colons (see EXAMPLES). The most commonly used environment variables,
USER, TERM, and PATH, are automatically imported to and exported from
the csh variables user, term, and path. Use setenv if you need to
change these variables. In addition, the shell sets the PWD environment
variable from the csh variable cwd whenever the latter changes.
The environment variables LC_CTYPE, LC_MESSAGES, LC_TIME, LC_COLLATE,
LC_NUMERIC, and LC_MONETARY take immediate effect when changed within
the C shell. See environ(5) for descriptions of these environment vari‐
ables.
unsetenv removes variable from the environment. As with unset, pattern
matching is not performed.
ksh
The flags for the set built-in have meaning as follows:
-A Array assignment. Unsets the variable name and assigns
values sequentially from the list arg. If +A is used, the
variable name is not unset first.
-a All subsequent variables that are defined are automati‐
cally exported.
-b Causes the shell to notify the user asynchronously of
background job completions.
-C Prevents existing files from being overwritten by the
shell's > redirection operator. The >| redirection opera‐
tor overrides this noclobber option for an individual
file.
-e If a command has a non-zero exit status, executes the ERR
trap, if set, and exits. This mode is disabled while read‐
ing profiles.
-f Disables file name generation.
-h Each command becomes a tracked alias when first encoun‐
tered.
-k All variable assignment arguments are placed in the envi‐
ronment for a command, not just those that precede the
command name.
-m Background jobs run in a separate process group and a line
prints 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 interac‐
tive shells.
-n Reads commands and checks them for syntax errors, but does
not execute them. Ignored for interactive shells.
+o Writes the current option stettings to standard output in
a format that is suitable for reinput to the shell as com‐
mands that achieve the same option settings.
-o option The option argument can be one of the following option
names:
allexport Same as -a.
errexit Same as -e.
bgnice All background jobs are run at a lower pri‐
ority. This is the default mode. emacs Puts
you in an emacs style in-line editor for
command entry.
gmacs Puts you in a gmacs style in-line editor for
command entry.
ignoreeof The shell does not exit on end-of-file. The
command exit must be used.
keyword Same as -k.
markdirs All directory names resulting from file name
generation have a trailing / appended.
monitor Same as -m.
noclobber Prevents redirection operator > from trun‐
cating existing files. Requires the >| oper‐
ator to truncate a file when turned on. Same
as -C.
noexec Same as -n.
noglob Same as -f.
nolog Does not save function definitions in his‐
tory file.
notify Same as -b.
nounset Same as -u.
privileged Same as -p.
verbose Same as -v.
trackall Same as -h.
vi Puts you in insert mode of a vi style in-
line editor until you hit escape character
033. This puts you in control mode. A return
sends the line.
viraw Each character is processed as it is typed
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
file /etc/suid_profile instead of the ENV file. This mode is on
whenever the effective uid is not equal to the real uid, or
when the effective gid is not equal to the real gid. Turning
this off causes the effective uid and gid to be set to the real
uid and gid.
-s Sorts the positional parameters lexicographically.
-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.
− Turns off -x and -v flags and stops examining arguments for
flags.
- Does not change any of the flags. This option is useful in set‐
ting $1 to a value beginning with −. If no arguments follow
this flag then the positional parameters are unset.
Using + rather than − causes these flags to be turned off. 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 specified then the names and values of all variables are
printed on the standard output.
The variables specified by the list of names are unassigned, that is,
their values and attributes are erased. readonly variables cannot be
unset. If the -f flag is set, then the names refer to function names.
Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS,
TMOUT, and _ removes their special meaning even if they are subse‐
quently assigned.
When using unset, the variables specified by the list of names are
unassigned, i.e., their values and attributes are erased. readonly
variables cannot be unset. If the -f, flag is set, then the names refer
to function names. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND,
RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if
they are subsequently assigned.
With the export built-in, the specified names are marked for automatic
export to the environment of subsequently-executed commands.
When -p is specified, export writes to the standard output the names
and values of all exported variables in the following format:
"export %s=%s\n", name, value
if name is set, and:
"export %s\n", name
if name is unset.
The shell formats the output, including the proper use of quoting, so
that it is suitable for reinput to the shell as commands that achieve
the same exporting results, except for the following:
1. Read-only variables with values cannot be reset.
2. Variables that were unset at the time they were output are
not reset to the unset state if a value is assigned to the
variable between the time the state was saved and the time
at which the saved output is reinput to the shell.
On this manual page, ksh(1) commands that are preceded by one or two *
(asterisks) are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in
effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. Words, following a command preceded by ** that are in the
format of a variable assignment, are expanded with the same
rules as a variable assignment. This means that tilde sub‐
stitution is performed after the = sign and word splitting
and file name generation are not performed.
ksh93
set sets or unsets options and positional parameters. Options that are
specified with a - cause the options to be set. Options that are speci‐
fied with a + cause the option to be unset.
set without any options or arguments displays the names and values of
all shell variables in the order of the collation sequence in the cur‐
rent locale. The values are quoted so that they are suitable for input
again to the shell.
If no arguments are specified, not even the end of options argument --,
the positional parameters are unchanged. Otherwise, unless the -A
option has been specified, the positional parameters are replaced by
the list of arguments. A first argument of -- is ignored when setting
positional parameters.
For backwards compatibility, a set command without any options speci‐
fied, whose first argument is - turns off the -v and -x options. If any
additional arguments are specified, they replace the positional parame‐
ters.
The options for set in ksh93 are:
-a Set the export attribute for each variable whose name
does not contain a . that you assign a value in the cur‐
rent shell environment.
-A name Assign the arguments sequentially to the array named by
name starting at subscript 0 rather than to the posi‐
tional parameters.
-b The shell writes a message to standard error as soon it
detects that a background job completes rather than
waiting until the next prompt.
-B Enable {...} group expansion. On by default.
-C Prevents existing regular files from being overwritten
using the > redirection operator. The >| redirection
overrides this noclobber option.
-e A simple command that has a non-zero exit status causes
the shell to exit unless the simple command is:
o contained in an && or || list
o the command immediately following if, while,
or until
o contained in the pipeline following !
-f Pathname expansion is disabled.
-G Causes ** by itself to also match all sub-directories
during pathname expansion.
-h Obsolete. Causes each command whose name has the syntax
of an alias to become a tracked alias when it is first
encountered.
-H Enable !-style history expansion similar to csh.
-k This is obsolete. All arguments of the form name=value
are removed and placed in the variable assignment list
for the command. Ordinarily, variable assignments must
precede command arguments.
-m When enabled, the shell runs background jobs in a sepa‐
rate process group and displays a line upon completion.
This mode is enabled by default for interactive shells
on systems that support job control.
-n The shell reads commands and checks for syntax errors,
but does not execute the command. Usually specified on
command invocation.
-o [option] If option is not specified, the list of options and
their current settings is written to standard output.
When invoked with a + the options are written in a for‐
mat that can be input again to the shell to restore the
settings. This option can be repeated to enable or dis‐
able multiple options.
The value of option must be one of the following:
allexport Same as -a.
bgnice All background jobs are run at lower pri‐
orities.
braceexpand Same as -B.
emacs Enables or disables emacs editing mode.
errexit Same as -e.
globstar Equivalent to -G.
gmacs Enables or disables gmacs. gmacs editing
mode is the same as emacs editing mode,
except for the handling of CTRL-T.
histexpand Same as -H.
ignoreeof The interactive shell does not exit on
end-of-file.
keyword Same as -k.
markdirs All directory names resulting from file
name generation have a trailing /
appended.
monitor Same as -m.
multiline Use multiple lines when editing lines
that are longer than the window width.
noclobber Same as -C.
noexec Same as -n.
noglob Same as -f.
nolog This has no effect. It is provided for
backward compatibility.
notify Same as -b.
nounset Same as -u.
pipefail A pipeline does not complete until all
components of the pipeline have com‐
pleted, and the exit status of the pipe‐
line is the value of the last command to
exit with non-zero exit status, or is
zero if all commands return zero exit
status.
privileged Same as -p.
showme Simple commands preceded by a ; are
traced as if -x were enabled but not exe‐
cuted.
trackall Same as -h.
verbose Same as -v.
vi Enables or disables vi editing mode.
viraw Does not use canonical input mode when
using vi edit mode
xtrace Same as -x.
-p Privileged mode. Disabling -p sets the effective user id
to the real user id, and the effective group id to the
real group id. Enabling -p restores the effective user
and group ids to their values when the shell was
invoked. The -p option is on whenever the real and
effective user id is not equal or the real and effective
group id is not equal. User profiles are not processed
when -p is enabled.
-r Restricted. Enables restricted shell. This option cannot
be unset once enabled.
-s Sort the positional parameters
-t Obsolete. The shell reads one command and then exits.
-u If enabled, the shell displays an error message when it
tries to expand a variable that is unset.
-v Verbose. The shell displays its input onto standard
error as it reads it.
-x Execution trace. The shell displays each command after
all expansion and before execution preceded by the
expanded value of the PS4 parameter.
The following exit values are returned by set in ksh93:
0 Successful completion.
>0 An error occurred.
For each name specified, unset unsets the variable, or function if -f
is specified, from the current shell execution environment. Read-only
variables cannot be unset.
The options for unset in ksh93 are:
-f Where name refers to a function name, the shell unsets the func‐
tion definition.
-n If name refers to variable that is a reference, the variable name
is unset rather than the variable it references. Otherwise, this
option is equivalent to the -v option.
-v Where name refers to a variable name, the shell unsets it and
removes it from the environment. This is the default behavior.
The following exit values are returned by unset in ksh93:
0 Successful completion. All names were successfully unset.
>0 An error occurred, or one or more name operands could not be
unset
export sets the export attribute on each of the variables specified by
name which causes them to be in the environment of subsequently exe‐
cuted commands. If =value is specified, the variable name is set to
value.
If no name is specified, the names and values of all exported variables
are written to standard output.
export is built-in to the shell as a declaration command so that field
splitting and pathname expansion are not performed on the arguments.
Tilde expansion occurs on value.
The options for export in ksh93 are:
-p Causes the output to be in the form of export commands that can
be used as input to the shell to recreate the current exports.
The following exit values are returned by export in ksh93:
0 Successful completion.
>0 An error occurred.
On this manual page, ksh93(1) commands that are preceded by one or two
+ are treated specially in the following ways:
1. Variable assignment lists preceding the command remain in
effect when the command completes.
2. I/O redirections are processed after variable assignments.
3. Errors cause a script that contains them to abort.
4. They are not valid function names.
5. Words, following a command preceded by ++ that are in the
format of a variable assignment, are expanded with the same
rules as a variable assignment. This means that tilde sub‐
stitution is performed after the = sign and field splitting
and file name generation are not performed.
EXAMPLES
csh
The following example sets the PATH variable to search for files in the
/bin, /usr/bin, /usr/sbin, and /usr/ucb/bin directories, in that order:
setenv PATH "/bin:/usr/bin:/usr/sbin:usr/ucb/bin"
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
┌─────────────────────────────┬─────────────────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├─────────────────────────────┼─────────────────────────────┤
│Availability │SUNWcs │
└─────────────────────────────┴─────────────────────────────┘
SEE ALSOcsh(1), ksh(1), ksh93(1), read(1), sh(1), typeset(1), attributes(5),
environ(5)SunOS 5.11 20 Nov 2007 set(1)
