set(1)
NAME
set, unset, setenv, unsetenv, export − shell built-in functions to determine the characteristics for environmental variables of the current 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 [ ±aefhkmnopstuvx ] [ ±o option ]... [ ±A name ] [ arg ... ]
unset [ −f ] name ...
†† export [ name[=value] ] ...
DESCRIPTION
sh
The set built-in command has the following options:
−a Mark variables which are modified or created for export.
−e Exit immediately if a command exits with a non-zero exit status.
−f Disable file name generation.
−h Locate and remember function commands as functions are defined (function commands are normally located when the function is executed).
−k All keyword arguments are placed in the environment for a command, not just those that precede the command name.
−n Read commands but do not execute them.
−t Exit after reading and executing one command.
−u Treat unset variables as an error when substituting.
−v Print shell input lines as they are read.
−x Print commands and their arguments as they are executed.
−− Do not change any of the flags; useful in setting $1 to −.
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 may be found in $−.
The remaining arguments are positional parameters and are assigned, in order, to $1, $2, .... If no arguments are given 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 IFS cannot be unset.
With the export built-in, the given names are marked for automatic export to the environment of subsequently executed commands. If no arguments are given, variable names that have been marked for export during the current shell’s execution are listed. (Variable names exported from a parent shell are listed only if they have been exported again during the current shell’s execution.) Function names are not exported.
csh
With no arguments, set displays the values of all shell variables. Multiword values are displayed as a parenthesized list. With the var argument 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) pattern. All variables are removed by ‘unset ∗’; this has noticeably distasteful side effects.
With no arguments, setenv displays all environment variables. With the VAR argument, setenv sets the environment variable VAR to have an empty (null) value. (By convention, environment variables are normally given upper-case names.) With both VAR and word arguments, setenv sets the environment variable NAME to the value word, which must be either a single word or a quoted string. The most commonly used environment variables, USER, TERM, and PATH, are automatically imported to and exported from the csh variables user, term, and path; there is no need to use setenv for these. 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.
If any of the LC_∗ variables ( LC_CTYPE, LC_MESSAGES, LC_TIME, LC_COLLATE, LC_NUMERIC, and LC_MONETARY ) (see environ(5)) are not set in the environment, the operational behavior of csh for each corresponding locale category is determined by the value of the LANG environment variable. If LC_ALL is set, its contents are used to override both the LANG and the other LC_∗ variables. If none of the above variables is set in the environment, the "C" (U.S. style) locale determines how csh behaves.
LC_CTYPE
Determines how csh handles characters. When LC_CTYPE is set to a valid value, csh can display and handle text and filenames containing valid characters for that locale. csh can display and handle Extended Unix Code (EUC) characters where any individual character can be 1, 2, or 3 bytes wide. csh can also handle EUC characters of 1, 2, or more column widths. In the "C" locale, only characters from ISO 8859-1 are valid.
LC_MESSAGES
Determines how diagnostic and informative messages are presented. This includes the language and style of the messages and the correct form of affirmative and negative responses. In the "C" locale, the messages are presented in the default form found in the program itself (in most cases, U.S./English).
LC_NUMERIC
Determines the value of the radix character (decimal point (".") in the "C" locale) and thousand separator (empty string ("") in the "C" locale).
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. Unset the variable name and assign 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 automatically exported.
−e If a command has a non-zero exit status, execute the ERR trap, if set, and exit. This mode is disabled while reading profiles.
−f Disables file name generation.
−h Each command becomes a tracked alias when first encountered.
−k All variable 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 Read commands and check them for syntax errors, but do not execute them. Ignored for interactive shells.
−o The following 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 priority. 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 will 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 > from truncating existing files. Require >│ to truncate a file when turned on.
noexec Same as −n.
noglob Same as −f.
nolog Do not save function definitions in history file.
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 Sort the positional parameters lexicographically.
−t Exit after reading and executing one command.
−u Treat unset parameters as an error when substituting.
−v Print shell input lines as they are read.
−x Print commands and their arguments as they are executed.
− Turns off −x and −v flags and stops examining arguments for flags.
−− Do not change any of the flags; useful in setting $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 may 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 then the names and values of all variables are printed on the standard output.
The variables given 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.
When using unset, the variables given 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 given names are marked for automatic export to the environment of subsequently-executed commands.
On this man page, ksh(1) commands that are preceded by one or two † (daggers) 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 substitution is performed after the = sign and word splitting and file name generation are not performed.
SEE ALSO
csh(1), ksh(1), read(1), sh(1), typeset(1)
SunOS 5.5/SPARC — Last change: 15 Apr 1994