| ZSHBUILTINS(1) | General Commands Manual | ZSHBUILTINS(1) |
zshbuiltins - zsh built-in commands
Some shell builtin commands take options as described in individual entries; these are often referred to in the list below as `flags' to avoid confusion with shell options, which may also have an effect on the behaviour of builtin commands. In this introductory section, `option' always has the meaning of an option to a command that should be familiar to most command line users.
Typically, options are single letters preceded by a hyphen (-). Options that take an argument accept it either immediately following the option letter or after white space, for example `print -C3 {1..9}' or `print -C 3 {1..9}' are equivalent. Arguments to options are not the same as arguments to the command; the documentation indicates which is which. Options that do not take an argument may be combined in a single word, for example `print -rca -- *' and `print -r -c -a -- *' are equivalent.
Some shell builtin commands also take options that begin with `+' instead of `-'. The list below makes clear which commands these are.
Options (together with their individual arguments, if any) must appear in a group before any non-option arguments; once the first non-option argument has been found, option processing is terminated.
All builtin commands other than `echo' and precommand modifiers, even those that have no options, can be given the argument `--' to terminate option processing. This indicates that the following words are non-option arguments, but is otherwise ignored. This is useful in cases where arguments to the command may begin with `-'. For historical reasons, most builtin commands (including `echo') also recognize a single `-' in a separate word for this purpose; note that this is less standard and use of `--' is recommended.
If file does not contain a slash, or if PATH_DIRS is set, the shell looks in the components of $path to find the directory containing file. Files in the current directory are not read unless `.' appears somewhere in $path. If a file named `file.zwc' is found, is newer than file, and is the compiled form (created with the zcompile builtin) of file, then commands are read from that file instead of file.
If any arguments arg are given, they become the positional parameters; the old positional parameters are restored when the file is done executing. However, if no arguments are given, the positional parameters remain those of the calling context, and no restoring is done.
If file was not found the return status is 127; if file was found but contained a syntax error the return status is 126; else the return status is the exit status of the last command executed.
% perldoc --help 2>&1 | grep 'built-in functions'
-f Search Perl built-in functions
% alias -g HG='--help 2>&1 | grep'
% perldoc HG 'built-in functions'
-f Search Perl built-in functions
If the -s flag is present, define a suffix alias: if the command word on a command line is in the form `text.name', where text is any non-empty string, it is replaced by the text `value text.name'. Note that name is treated as a literal string, not a pattern. A trailing space in value is not special in this case. For example,
alias -s ps='gv --'
will cause the command `*.ps' to be expanded to `gv -- *.ps'. As alias expansion is carried out earlier than globbing, the `*.ps' will then be expanded. Suffix aliases constitute a different name space from other aliases (so in the above example it is still possible to create an alias for the command ps) and the two sets are never listed together.
For each name with no value, print the value of name, if any. With no arguments, print all currently defined aliases other than suffix aliases. If the -m flag is given the arguments are taken as patterns (they should be quoted to preserve them from being interpreted as glob patterns), and the aliases matching these patterns are printed. When printing aliases and one of the -g, -r or -s flags is present, restrict the printing to global, regular or suffix aliases, respectively; a regular alias is one which is neither a global nor a suffix alias. Using `+' instead of `-', or ending the option list with a single `+', prevents the values of the aliases from being printed.
If the -L flag is present, then print each alias in a manner suitable for putting in a startup script. The exit status is nonzero if a name (with no value) is given for which no alias has been defined.
For more on aliases, include common problems, see the section ALIASING in zshmisc(1).
If name consists of an absolute path, the function is defined to load from the file given (searching as usual for dump files in the given location). The name of the function is the basename (non-directory part) of the file. It is normally an error if the function is not found in the given location; however, if the option -d is given, searching for the function defaults to $fpath. If a function is loaded by absolute path, any functions loaded from it that are marked for autoload without an absolute path have the load path of the parent function temporarily prepended to $fpath.
If the option -r or -R is given, the function is searched for immediately and the location is recorded internally for use when the function is executed; a relative path is expanded using the value of $PWD. This protects against a change to $fpath after the call to autoload. With -r, if the function is not found, it is silently left unresolved until execution; with -R, an error message is printed and command processing aborted immediately the search fails, i.e. at the autoload command rather than at function execution..
The flag -X may be used only inside a shell function. It causes the calling function to be marked for autoloading and then immediately loaded and executed, with the current array of positional parameters as arguments. This replaces the previous definition of the function. If no function definition is found, an error is printed and the function remains undefined and marked for autoloading. If an argument is given, it is used as a directory (i.e. it does not include the name of the function) in which the function is to be found; this may be combined with the -d option to allow the function search to default to $fpath if it is not in the given location.
The flag +X attempts to load each name as an autoloaded function, but does not execute it. The exit status is zero (success) if the function was not previously defined and a definition for it was found. This does not replace any existing definition of the function. The exit status is nonzero (failure) if the function was already defined or when no definition was found. In the latter case the function remains undefined and marked for autoloading. If ksh-style autoloading is enabled, the function created will contain the contents of the file plus a call to the function itself appended to it, thus giving normal ksh autoloading behaviour on the first call to the function. If the -m flag is also given each name is treated as a pattern and all functions already marked for autoload that match the pattern are loaded.
With the -t flag, turn on execution tracing; with -T, turn on execution tracing only for the current function, turning it off on entry to any called functions that do not also have tracing enabled.
With the -U flag, alias expansion is suppressed when the function is loaded.
With the -w flag, the names are taken as names of files compiled with the zcompile builtin, and all functions defined in them are marked for autoloading.
The flags -z and -k mark the function to be autoloaded using the zsh or ksh style, as if the option KSH_AUTOLOAD were unset or were set, respectively. The flags override the setting of the option at the time the function is loaded.
Note that the autoload command makes no attempt to ensure the shell options set during the loading or execution of the file have any particular value. For this, the emulate command can be used:
emulate zsh -c 'autoload -Uz func'
arranges that when func is loaded the shell is in native zsh emulation, and this emulation is also applied when func is run.
Some of the functions of autoload are also provided by functions -u or functions -U, but autoload is a more comprehensive interface.
Otherwise, if arg begins with a slash, attempt to change to the directory given by arg.
If arg does not begin with a slash, the behaviour depends on whether the current directory `.' occurs in the list of directories contained in the shell parameter cdpath. If it does not, first attempt to change to the directory arg under the current directory, and if that fails but cdpath is set and contains at least one element attempt to change to the directory arg under each component of cdpath in turn until successful. If `.' occurs in cdpath, then cdpath is searched strictly in order so that `.' is only tried at the appropriate point.
The order of testing cdpath is modified if the option POSIX_CD is set, as described in the documentation for the option.
If no directory is found, the option CDABLE_VARS is set, and a parameter named arg exists whose value begins with a slash, treat its value as the directory. In that case, the parameter is added to the named directory hash table.
The second form of cd substitutes the string new for the string old in the name of the current directory, and tries to change to this new directory.
The third form of cd extracts an entry from the directory stack, and changes to that directory. An argument of the form `+n' identifies a stack entry by counting from the left of the list shown by the dirs command, starting with zero. An argument of the form `-n' counts from the right. If the PUSHD_MINUS option is set, the meanings of `+' and `-' in this context are swapped. If the POSIX_CD option is set, this form of cd is not recognised and will be interpreted as the first form.
If the -q (quiet) option is specified, the hook function chpwd and the functions in the array chpwd_functions are not called. This is useful for calls to cd that do not change the environment seen by an interactive user.
If the -s option is specified, cd refuses to change the current directory if the given pathname contains symlinks. If the -P option is given or the CHASE_LINKS option is set, symbolic links are resolved to their true values. If the -L option is given symbolic links are retained in the directory (and not resolved) regardless of the state of the CHASE_LINKS option.
See also the section `Precommand Modifiers' in zshmisc(1).
With the option -p, name ... refer to elements of the shell's pattern syntax as described in the section `Filename Generation'. Certain elements can be disabled separately, as given below.
Note that patterns not allowed by the current settings for the options EXTENDED_GLOB, KSH_GLOB and SH_GLOB are never enabled, regardless of the setting here. For example, if EXTENDED_GLOB is not active, the pattern ^ is ineffective even if `disable -p "^"' has not been issued. The list below indicates any option settings that restrict the use of the pattern. It should be noted that setting SH_GLOB has a wider effect than merely disabling patterns as certain expressions, in particular those involving parentheses, are parsed differently.
The following patterns may be disabled; all the strings need quoting on the command line to prevent them from being interpreted immediately as patterns and the patterns are shown below in single quotes as a reminder.
If the jobs are currently stopped and the AUTO_CONTINUE option is not set, a warning is printed containing information about how to make them running after they have been disowned. If one of the latter two forms is used, the jobs will automatically be made running, independent of the setting of the AUTO_CONTINUE option.
The -E flag, or the BSD_ECHO option, can be used to disable these escape sequences. In the latter case, -e flag can be used to enable them.
Note that for standards compliance a double dash does not terminate option processing; instead, it is printed directly. However, a single dash does terminate option processing, so the first dash, possibly following options, is not printed, but everything following it is printed as an argument. The single dash behaviour is different from other shells. For a more portable way of printing text, see printf, and for a more controllable way of printing text within zsh, see print.
With single argument set up zsh options to emulate the specified shell as much as possible. csh will never be fully emulated. If the argument is not one of the shells listed above, zsh will be used as a default; more precisely, the tests performed on the argument are the same as those used to determine the emulation at startup based on the shell name, see the section COMPATIBILITY in zsh(1) . In addition to setting shell options, the command also restores the pristine state of pattern enables, as if all patterns had been enabled using enable -p.
If the emulate command occurs inside a function that has been marked for execution tracing with functions -t then the xtrace option will be turned on regardless of emulation mode or other options. Note that code executed inside the function by the ., source, or eval commands is not considered to be running directly from the function, hence does not provoke this behaviour.
If the -R switch is given, all settable options are reset to their default value corresponding to the specified emulation mode, except for certain options describing the interactive environment; otherwise, only those options likely to cause portability problems in scripts and functions are altered. If the -L switch is given, the options LOCAL_OPTIONS, LOCAL_PATTERNS and LOCAL_TRAPS will be set as well, causing the effects of the emulate command and any setopt, disable -p or enable -p, and trap commands to be local to the immediately surrounding shell function, if any; normally these options are turned off in all emulation modes except ksh. The -L switch is mutually exclusive with the use of -c in flags.
If there is a single argument and the -l switch is given, the options that would be set or unset (the latter indicated with the prefix `no') are listed. -l can be combined with -L or -R and the list will be modified in the appropriate way. Note the list does not depend on the current setting of options, i.e. it includes all options that may in principle change, not just those that would actually change.
The flags may be any of the invocation-time flags described in the section INVOCATION in zsh(1), except that `-o EMACS' and `-o VI' may not be used. Flags such as `+r'/`+o RESTRICTED' may be prohibited in some circumstances.
If -c arg appears in flags, arg is evaluated while the requested emulation is temporarily in effect. In this case the emulation mode and all options are restored to their previous values before emulate returns. The -R switch may precede the name of the shell to emulate; note this has a meaning distinct from including -R in flags.
Use of -c enables `sticky' emulation mode for functions defined within the evaluated expression: the emulation mode is associated thereafter with the function so that whenever the function is executed the emulation (respecting the -R switch, if present) and all options are set (and pattern disables cleared) before entry to the function, and the state is restored after exit. If the function is called when the sticky emulation is already in effect, either within an `emulate shell -c' expression or within another function with the same sticky emulation, entry and exit from the function do not cause options to be altered (except due to standard processing such as the LOCAL_OPTIONS option). This also applies to functions marked for autoload within the sticky emulation; the appropriate set of options will be applied at the point the function is loaded as well as when it is run.
For example:
emulate sh -c 'fni() { setopt cshnullglob; }
fno() { fni; }'
fno
The two functions fni and fno are defined with sticky sh emulation. fno is then executed, causing options associated with emulations to be set to their values in sh. fno then calls fni; because fni is also marked for sticky sh emulation, no option changes take place on entry to or exit from it. Hence the option cshnullglob, turned off by sh emulation, will be turned on within fni and remain on return to fno. On exit from fno, the emulation mode and all options will be restored to the state they were in before entry to the temporary emulation.
The documentation above is typically sufficient for the intended purpose of executing code designed for other shells in a suitable environment. More detailed rules follow.
enable -p reenables patterns disabled with disable -p. Note that it does not override globbing options; for example, `enable -p "~"' does not cause the pattern character ~ to be active unless the EXTENDED_GLOB option is also set. To enable all possible patterns (so that they may be individually disabled with disable -p), use `setopt EXTENDED_GLOB KSH_GLOB NO_SH_GLOB'.
With -c clear the environment; with -l prepend - to the argv[0] string of the command executed (to simulate a login shell); with -a argv0 set the argv[0] string of the command executed. See the section `Precommand Modifiers' in zshmisc(1).
If the option POSIX_BUILTINS is set, command is never interpreted as a shell builtin command or shell function. This means further precommand modifiers such as builtin and noglob are also not interpreted within the shell. Hence command is always found by searching the command path.
If command is omitted but any redirections are specified, then the redirections will take effect in the current shell.
See notes at the end of the section JOBS in zshmisc(1) for some possibly unexpected interactions of the exit command with jobs.
The first two forms of this command select a range of events from first to last from the history list. The arguments first and last may be specified as a number or as a string. A negative number is used as an offset to the current history event number. A string specifies the most recent event beginning with the given string. All substitutions old=new, if any, are then performed on the text of the events.
The range of events selected by numbers can be narrowed further by the following flags.
If first is not specified, it will be set to -1 (the most recent event), or to -16 if the -l flag is given. If last is not specified, it will be set to first, or to -1 if the -l flag is given. However, if the current event has added entries to the history with `print -s' or `fc -R', then the default last for -l includes all new history entries since the current event began.
When the -l flag is given, the resulting events are listed on standard output. Otherwise the editor program specified by -e ename is invoked on a file containing these history events. If -e is not given, the value of the parameter FCEDIT is used; if that is not set the value of the parameter EDITOR is used; if that is not set a builtin default, usually `vi' is used. If ename is `-', no editor is invoked. When editing is complete, the edited command is executed.
The flag `-s' is equivalent to `-e -'. The flag -r reverses the order of the events and the flag -n suppresses event numbers when listing.
Also when listing,
`fc -p' pushes the current history list onto a stack and switches to a new history list. If the -a option is also specified, this history list will be automatically popped when the current function scope is exited, which is a much better solution than creating a trap function to call `fc -P' manually. If no arguments are specified, the history list is left empty, $HISTFILE is unset, and $HISTSIZE & $SAVEHIST are set to their default values. If one argument is given, $HISTFILE is set to that filename, $HISTSIZE & $SAVEHIST are left unchanged, and the history file is read in (if it exists) to initialize the new list. If a second argument is specified, $HISTSIZE & $SAVEHIST are instead set to the single specified numeric value. Finally, if a third argument is specified, $SAVEHIST is set to a separate value from $HISTSIZE. You are free to change these environment values for the new history list however you desire in order to manipulate the new history list.
`fc -P' pops the history list back to an older list saved by `fc -p'. The current list is saved to its $HISTFILE before it is destroyed (assuming that $HISTFILE and $SAVEHIST are set appropriately, of course). The values of $HISTFILE, $HISTSIZE, and $SAVEHIST are restored to the values they had when `fc -p' was called. Note that this restoration can conflict with making these variables "local", so your best bet is to avoid local declarations for these variables in functions that use `fc -p'. The one other guaranteed-safe combination is declaring these variables to be local at the top of your function and using the automatic option (-a) with `fc -p'. Finally, note that it is legal to manually pop a push marked for automatic popping if you need to do so before the function exits.
`fc -R' reads the history from the given file, `fc -W' writes the history out to the given file, and `fc -A' appends the history out to the given file. If no filename is specified, the $HISTFILE is assumed. If the -I option is added to -R, only those events that are not already contained within the internal history list are added. If the -I option is added to -A or -W, only those events that are new since last incremental append/write to the history file are appended/written. In any case, the created file will have no more than $SAVEHIST entries.
The -x option indicates that any functions output will have each leading tab for indentation, added by the shell to show syntactic structure, expanded to the given number num of spaces. num can also be 0 to suppress all indentation.
The -W option turns on the option WARN_NESTED_VAR for the named function or functions only. The option is turned off at the start of nested functions (apart from anonoymous functions) unless the called function also has the -W attribute.
The -c option causes oldfn to be copied to newfn. The copy is efficiently handled internally by reference counting. If oldfn was marked for autoload it is first loaded and if this fails the copy fails. Either function may subsequently be redefined without affecting the other. A typical idiom is that oldfn is the name of a library shell function which is then redefined to call newfn, thereby installing a modified version of the function.
The -M and +M flags
Use of the -M option may not be combined with any of the options handled by typeset -f.
functions -M mathfn defines mathfn as the name of a mathematical function recognised in all forms of arithmetical expressions; see the section `Arithmetic Evaluation' in zshmisc(1). By default mathfn may take any number of comma-separated arguments. If min is given, it must have exactly min args; if min and max are both given, it must have at least min and at most max args. max may be -1 to indicate that there is no upper limit.
By default the function is implemented by a shell function of the same name; if shellfn is specified it gives the name of the corresponding shell function while mathfn remains the name used in arithmetical expressions. The name of the function in $0 is mathfn (not shellfn as would usually be the case), provided the option FUNCTION_ARGZERO is in effect. The positional parameters in the shell function correspond to the arguments of the mathematical function call.
The result of the last arithmetical expression evaluated inside the shell function gives the result of the mathematical function. This is not limited to arithmetic substitutions of the form $((...)), but also includes arithmetical expressions evaluated in any other way, including by the let builtin, by ((...)) statements, and even by the return builtin and by array subscripts. Therefore, care must be taken not to use syntactical constructs that perform arithmetic evaluation after evaluating what is to be the result of the function. For example:
# WRONG
zmath_cube() {
(( $1 * $1 * $1 ))
return 0
}
functions -M cube 1 1 zmath_cube
print $(( cube(3) ))
This will print `0' because of the return.
Commenting the return out would lead to a different problem: the ((...)) statement would become the last statement in the function, so the return status ($?) of the function would be non-zero (indicating failure) whenever the arithmetic result of the function would happen to be zero (numerically):
# WRONG
zmath_cube() {
(( $1 * $1 * $1 ))
}
functions -M cube 1 1 zmath_cube
print $(( cube(0) ))
Instead, the true builtin can be used:
# RIGHT
zmath_cube() {
(( $1 * $1 * $1 ))
true
}
functions -M cube 1 1 zmath_cube
print $(( cube(3) ))
If the additional option -s is given to functions -M, the argument to the function is a single string: anything between the opening and matching closing parenthesis is passed to the function as a single argument, even if it includes commas or white space. The minimum and maximum argument specifiers must therefore be 1 if given. An empty argument list is passed as a zero-length string. Thus, the following string function takes a single argument, including the commas, and prints 11:
stringfn() { (( $#1 )); true }
functions -Ms stringfn
print $(( stringfn(foo,bar,rod) ))
functions -M with no arguments lists all such user-defined functions in the same form as a definition. With the additional option -m and a list of arguments, all functions whose mathfn matches one of the pattern arguments are listed.
function +M removes the list of mathematical functions; with the additional option -m the arguments are treated as patterns and all functions whose mathfn matches the pattern are removed. Note that the shell function implementing the behaviour is not removed (regardless of whether its name coincides with mathfn).
Each time it is invoked, getopts places the option letter it finds in the shell parameter name, prepended with a `+' when arg begins with a `+'. The index of the next arg is stored in OPTIND. The option argument, if any, is stored in OPTARG.
The first option to be examined may be changed by explicitly assigning to OPTIND. OPTIND has an initial value of 1, and is normally set to 1 upon entry to a shell function and restored upon exit. (The POSIX_BUILTINS option disables this, and also changes the way the value is calculated to match other shells.) OPTARG is not reset and retains its value from the most recent call to getopts. If either of OPTIND or OPTARG is explicitly unset, it remains unset, and the index or option argument is not stored. The option itself is still stored in name in this case.
A leading `:' in optstring causes getopts to store the letter of any invalid option in OPTARG, and to set name to `?' for an unknown option and to `:' when a required argument is missing. Otherwise, getopts sets name to `?' and prints an error message when an option is invalid. The exit status is nonzero when there are no more options.
A command name starting with a / is never hashed, whether by explicit use of the hash command or otherwise. Such a command is always found by direct look up in the file system.
Given no arguments, and neither the -r or -f options, the selected hash table will be listed in full.
The -r option causes the selected hash table to be emptied. It will be subsequently rebuilt in the normal fashion. The -f option causes the selected hash table to be fully rebuilt immediately. For the command hash table this hashes all the absolute directories in the PATH, and for the named directory hash table this adds all users' home directories. These two options cannot be used with any arguments.
The -m option causes the arguments to be taken as patterns (which should be quoted) and the elements of the hash table matching those patterns are printed. This is the only way to display a limited selection of hash table elements.
For each name with a corresponding value, put `name' in the selected hash table, associating it with the pathname `value'. In the command hash table, this means that whenever `name' is used as a command argument, the shell will try to execute the file given by `value'. In the named directory hash table, this means that `value' may be referred to as `~name'.
For each name with no corresponding value, attempt to add name to the hash table, checking what the appropriate value is in the normal manner for that hash table. If an appropriate value can't be found, then the hash table will be unchanged.
The -v option causes hash table entries to be listed as they are added by explicit specification. If has no effect if used with -f.
If the -L flag is present, then each hash table entry is printed in the form of a call to hash.
The -Z option replaces the shell's argument and environment space with the given string, truncated if necessary to fit. This will normally be visible in ps (ps(1)) listings. This feature is typically used by daemons, to indicate their state.
Full job control is only available in the top-level interactive shell, not in commands run in the left hand side of pipelines or within the (...) construct. However, a snapshot of the job state at that point is taken, so it is still possible to use the jobs builtin, or any parameter providing job information. This gives information about the state of jobs at the point the subshell was created. If background processes are created within the subshell, then instead information about those processes is provided.
For example,
sleep 10 & # Job in background ( # Shell forks jobs # Shows information about "sleep 10 &" sleep 5 & # Process in background (no job control) jobs # Shows information about "sleep 5 &" )
On some systems, alternative signal names are allowed for a few signals. Typical examples are SIGCHLD and SIGCLD or SIGPOLL and SIGIO, assuming they correspond to the same signal number. kill -l will only list the preferred form, however kill -l alt will show if the alternative form corresponds to a signal number. For example, under Linux kill -l IO and kill -l POLL both output 29, hence kill -IO and kill -POLL have the same effect.
Many systems will allow process IDs to be negative to kill a process group or zero to kill the current process group.
If limit is not specified, print the current limit placed on resource, otherwise set the limit to the specified value. If the -h flag is given, use hard limits instead of soft limits. If no resource is given, print all limits.
When looping over multiple resources, the shell will abort immediately if it detects a badly formed argument. However, if it fails to set a limit for some other reason it will continue trying to set the remaining limits.
resource can be one of:
Which of these resource limits are available depends on the system. resource can be abbreviated to any unambiguous prefix. It can also be an integer, which corresponds to the integer defined for the resource by the operating system.
If argument corresponds to a number which is out of the range of the resources configured into the shell, the shell will try to read or write the limit anyway, and will report an error if this fails. As the shell does not store such resources internally, an attempt to set the limit will fail unless the -s option is present.
limit is a number, with an optional scaling factor, as follows:
The limit command is not made available by default when the shell starts in a mode emulating another shell. It can be made available with the command `zmodload -F zsh/rlimits b:limit'.
If the -q (quiet) option is specified, the hook function chpwd and the functions in the array $chpwd_functions are not called, and the new directory stack is not printed. This is useful for calls to popd that do not change the environment seen by an interactive user.
The start of the output of each print command is assumed to be aligned with a tab stop. Widths of multibyte characters are handled if the option MULTIBYTE is in effect. This option is ignored if other formatting options are in effect, namely column alignment or printf style, or if output is to a special location such as shell history or the command line editor.
If any of `-m', `-o' or `-O' are used in combination with `-f' and there are no arguments (after the removal process in the case of `-m') then nothing is printed.
Normally, conversion specifications are applied to each argument in order but they can explicitly specify the nth argument is to be used by replacing `%' by `%n$' and `*' by `*n$'. It is recommended that you do not mix references of this explicit style with the normal style and the handling of such mixed styles may be subject to future change.
If arguments remain unused after formatting, the format string is reused until all arguments have been consumed. With the print builtin, this can be suppressed by using the -r option. If more arguments are required by the format than have been specified, the behaviour is as if zero or an empty string had been specified as the argument.
The -v option causes the output to be stored as the value of the parameter name, instead of printed. If name is an array and the format string is reused when consuming arguments then one array element will be used for each use of the format string.
The third form of pushd changes directory by rotating the directory list. An argument of the form `+n' identifies a stack entry by counting from the left of the list shown by the dirs command, starting with zero. An argument of the form `-n' counts from the right. If the PUSHD_MINUS option is set, the meanings of `+' and `-' in this context are swapped.
If the -q (quiet) option is specified, the hook function chpwd and the functions in the array $chpwd_functions are not called, and the new directory stack is not printed. This is useful for calls to pushd that do not change the environment seen by an interactive user.
If the option -q is not specified and the shell option PUSHD_SILENT is not set, the directory stack will be printed after a pushd is performed.
The options -s, -L and -P have the same meanings as for the cd builtin.
Note that despite the mnemonic `key' this option does read full characters, which may consist of multiple bytes if the option MULTIBYTE is set.
This option is not available when reading from the editor buffer with -z, when called from within completion with -c or -l, with -q which clears the input queue before reading, or within zle where other mechanisms should be used to test for input.
Note that read does not attempt to alter the input processing mode. The default mode is canonical input, in which an entire line is read at a time, so usually `read -t' will not read anything until an entire line has been typed. However, when reading from the terminal with -k input is processed one key at a time; in this case, only availability of the first character is tested, so that e.g. `read -t -k 2' can still block on the second character. Use two instances of `read -t -k' if this is not what is wanted.
If the first argument contains a `?', the remainder of this word is used as a prompt on standard error when the shell is interactive.
The value (exit status) of read is 1 when an end-of-file is encountered, or when -c or -l is present and the command is not called from a compctl function, or as described for -q. Otherwise the value is 0.
The behavior of some combinations of the -k, -p, -q, -u and -z flags is undefined. Presently -q cancels all the others, -p cancels -u, -k cancels -z, and otherwise -z cancels both -p and -u.
The -c or -l flags cancel any and all of -kpquz.
() { integer foo=40; return "foo + 2" }
echo $?
If n is omitted, the return status is that of the last command executed.
If return was executed from a trap in a TRAPNAL function, the effect is different for zero and non-zero return status. With zero status (or after an implicit return at the end of the trap), the shell will return to whatever it was previously processing; with a non-zero status, the shell will behave as interrupted except that the return status of the trap is retained. Note that the numeric value of the signal which caused the trap is passed as the first argument, so the statement `return "128+$1"' will return the same status as if the signal had not been trapped.
If the -A flag is specified, name is set to an array containing the given args; if no name is specified, all arrays are printed together with their values.
If +A is used and name is an array, the given arguments will replace the initial elements of that array; if no name is specified, all arrays are printed without their values.
The behaviour of arguments after -A name or +A name depends on whether the option KSH_ARRAYS is set. If it is not set, all arguments following name are treated as values for the array, regardless of their form. If the option is set, normal option processing continues at that point; only regular arguments are treated as values for the array. This means that
set -A array -x -- foo
sets array to `-x -- foo' if KSH_ARRAYS is not set, but sets the array to foo and turns on the option `-x' if it is set.
If the -A flag is not present, but there are arguments beyond the options, the positional parameters are set. If the option list (if any) is terminated by `--', and there are no further arguments, the positional parameters will be unset.
If no arguments and no `--' are given, then the names and values of all parameters are printed on the standard output. If the only argument is `+', the names of all parameters are printed.
For historical reasons, `set -' is treated as `set +xv' and `set - args' as `set +xv -- args' when in any other emulation mode than zsh's native mode.
If no arguments are supplied, the names of all options currently set are printed. The form is chosen so as to minimize the differences from the default options for the current emulation (the default emulation being native zsh, shown as <Z> in zshoptions(1)). Options that are on by default for the emulation are shown with the prefix no only if they are off, while other options are shown without the prefix no and only if they are on. In addition to options changed from the default state by the user, any options activated automatically by the shell (for example, SHIN_STDIN or INTERACTIVE) will be shown in the list. The format is further modified by the option KSH_OPTION_PRINT, however the rationale for choosing options with or without the no prefix remains the same in this case.
If the -m flag is given the arguments are taken as patterns (which should be quoted to protect them from filename expansion), and all options with names matching these patterns are set.
Note that a bad option name does not cause execution of subsequent shell code to be aborted; this is behaviour is different from that of `set -o'. This is because set is regarded as a special builtin by the POSIX standard, but setopt is not.
If the option -p is given arguments are instead removed (popped) from the end rather than the start of the array.
The command attempts to implement POSIX and its extensions where these are specified. Unfortunately there are intrinsic ambiguities in the syntax; in particular there is no distinction between test operators and strings that resemble them. The standard attempts to resolve these for small numbers of arguments (up to four); for five or more arguments compatibility cannot be relied on. Users are urged wherever possible to use the `[[' test syntax which does not have these ambiguities.
If arg is `-', then the specified signals are reset to their defaults, or, if no sig args are present, all traps are reset.
If arg is an empty string, then the specified signals are ignored by the shell (and by the commands it invokes).
If arg is omitted but one or more sig args are provided (i.e. the first argument is a valid signal number or name), the effect is the same as if arg had been specified as `-'.
The trap command with no arguments prints a list of commands associated with each signal.
If sig is ZERR then arg will be executed after each command with a nonzero exit status. ERR is an alias for ZERR on systems that have no SIGERR signal (this is the usual case).
If sig is DEBUG then arg will be executed before each command if the option DEBUG_BEFORE_CMD is set (as it is by default), else after each command. Here, a `command' is what is described as a `sublist' in the shell grammar, see the section SIMPLE COMMANDS & PIPELINES in zshmisc(1). If DEBUG_BEFORE_CMD is set various additional features are available. First, it is possible to skip the next command by setting the option ERR_EXIT; see the description of the ERR_EXIT option in zshoptions(1). Also, the shell parameter ZSH_DEBUG_CMD is set to the string corresponding to the command to be executed following the trap. Note that this string is reconstructed from the internal format and may not be formatted the same way as the original text. The parameter is unset after the trap is executed.
If sig is 0 or EXIT and the trap statement is executed inside the body of a function, then the command arg is executed after the function completes. The value of $? at the start of execution is the exit status of the shell or the return status of the function exiting. If sig is 0 or EXIT and the trap statement is not executed inside the body of a function, then the command arg is executed when the shell terminates; the trap runs before any zshexit hook functions.
ZERR, DEBUG, and EXIT traps are not executed inside other traps. ZERR and DEBUG traps are kept within subshells, while other traps are reset.
Note that traps defined with the trap builtin are slightly different from those defined as `TRAPNAL () { ... }', as the latter have their own function environment (line numbers, local variables, etc.) while the former use the environment of the command in which they were called. For example,
trap 'print $LINENO' DEBUG
will print the line number of a command executed after it has run, while
TRAPDEBUG() { print $LINENO; }
will always print the number zero.
Alternative signal names are allowed as described under kill above. Defining a trap under either name causes any trap under an alternative name to be removed. However, it is recommended that for consistency users stick exclusively to one name or another.
Without options it reports whether the terminal is frozen or not.
Note that, regardless of whether the tty is frozen or not, the shell needs to change the settings when the line editor starts, so unfreezing the tty does not guarantee settings made on the command line are preserved. Strings of commands run between editing the command line will see a consistent tty state. See also the shell variable STTY for a means of initialising the tty before running external commands and/or freezing the tty around a single command.
Except as noted below for control flags that change the behavior, a parameter is created for each name that does not already refer to one. When inside a function, a new parameter is created for every name (even those that already exist), and is unset again when the function completes. See `Local Parameters' in zshparam(1). The same rules apply to special shell parameters, which retain their special attributes when made local.
For each name=value assignment, the parameter name is set to value. If the assignment is omitted and name does not refer to an existing parameter, a new parameter is intialized to empty string, zero, or empty array (as appropriate), unless the shell option TYPESET_TO_UNSET is set. When that option is set, the parameter attributes are recorded but the parameter remains unset.
If the shell option TYPESET_SILENT is not set, for each remaining name that refers to a parameter that is already set, the name and value of the parameter are printed in the form of an assignment. Nothing is printed for newly-created parameters, or when any attribute flags listed below are given along with the name. Using `+' instead of minus to introduce an attribute turns it off.
If no name is present, the names and values of all parameters are printed. In this case the attribute flags restrict the display to only those parameters that have the specified attributes, and using `+' rather than `-' to introduce the flag suppresses printing of the values of parameters when there is no parameter name.
All forms of the command handle scalar assignment. Array assignment is possible if any of the reserved words declare, export, float, integer, local, readonly or typeset is matched when the line is parsed (N.B. not when it is executed). In this case the arguments are parsed as assignments, except that the `+=' syntax and the GLOB_ASSIGN option are not supported, and scalar values after = are not split further into words, even if expanded (regardless of the setting of the KSH_TYPESET option; this option is obsolete).
Examples of the differences between command and reserved word parsing:
# Reserved word parsing typeset svar=$(echo one word) avar=(several words)
The above creates a scalar parameter svar and an array parameter avar as if the assignments had been
svar="one word" avar=(several words)
On the other hand:
# Normal builtin interface builtin typeset svar=$(echo two words)
The builtin keyword causes the above to use the standard builtin interface to typeset in which argument parsing is performed in the same way as for other commands. This example creates a scalar svar containing the value two and another scalar parameter words with no value. An array value in this case would either cause an error or be treated as an obscure set of glob qualifiers.
Arbitrary arguments are allowed if they take the form of assignments after command line expansion; however, these only perform scalar assignment:
var='svar=val' typeset $var
The above sets the scalar parameter svar to the value val. Parentheses around the value within var would not cause array assignment as they will be treated as ordinary characters when $var is substituted. Any non-trivial expansion in the name part of the assignment causes the argument to be treated in this fashion:
typeset {var1,var2,var3}=name
The above syntax is valid, and has the expected effect of setting the three parameters to the same value, but the command line is parsed as a set of three normal command line arguments to typeset after expansion. Hence it is not possible to assign to multiple arrays by this means.
Note that each interface to any of the commands may be disabled separately. For example, `disable -r typeset' disables the reserved word interface to typeset, exposing the builtin interface, while `disable typeset' disables the builtin. Note that disabling the reserved word interface for typeset may cause problems with the output of `typeset -p', which assumes the reserved word interface is available in order to restore array and associative array values.
Unlike parameter assignment statements, typeset's exit status on an assignment that involves a command substitution does not reflect the exit status of the command substitution. Therefore, to test for an error in a command substitution, separate the declaration of the parameter from its initialization:
# WRONG typeset var1=$(exit 1) || echo "Trouble with var1" # RIGHT typeset var1 && var1=$(exit 1) || echo "Trouble with var1"
To initialize a parameter param to a command output and mark it readonly, use typeset -r param or readonly param after the parameter assignment statement.
If no attribute flags are given, and either no name arguments are present or the flag +m is used, then each parameter name printed is preceded by a list of the attributes of that parameter (array, association, exported, float, integer, readonly, or undefined for autoloaded parameters not yet loaded). If +m is used with attribute flags, and all those flags are introduced with +, the matching parameter names are printed but their values are not.
The following control flags change the behavior of typeset:
If the +g flag is combined with -m, a new local parameter is created for every matching parameter that is not already local. Otherwise -m applies all other flags or assignments to the existing parameters.
Except when assignments are made with name=value, using +m forces the matching parameters and their attributes to be printed, even inside a function. Note that -m is ignored if no patterns are given, so `typeset -m' displays attributes but `typeset -a +m' does not.
-p may be followed by an optional integer argument. Currently only the value 1 is supported. In this case arrays and associative arrays are printed with newlines between indented elements for readability.
Only one of the scalar and array parameters may be assigned an initial value (the restrictions on assignment forms described above also apply).
Both the scalar and the array may be manipulated as normal. If one is unset, the other will automatically be unset too. There is no way of untying the variables without unsetting them, nor of converting the type of one of them with another typeset command; +T does not work, assigning an array to scalar is an error, and assigning a scalar to array sets it to be a single-element array.
Note that both `typeset -xT ...' and `export -T ...' work, but only the scalar will be marked for export. Setting the value using the scalar version causes a split on all separators (which cannot be quoted). It is possible to apply -T to two previously tied variables but with a different separator character, in which case the variables remain joined as before but the separator is changed.
When an existing scalar is tied to a new array, the value of the scalar is preserved but no attribute other than export will be preserved.
Attribute flags that transform the final value (-L, -R, -Z, -l, -u) are only applied to the expanded value at the point of a parameter expansion expression using `$'. They are not applied when a parameter is retrieved internally by the shell for any purpose.
The following attribute flags may be specified:
The width is the count of characters, which may be multibyte characters if the MULTIBYTE option is in effect. Note that the screen width of the character is not taken into account; if this is required, use padding with parameter expansion flags ${(ml...)...} as described in `Parameter Expansion Flags' in zshexpn(1).
When the parameter is expanded, it is filled on the right with blanks or truncated if necessary to fit the field. Note truncation can lead to unexpected results with numeric parameters. Leading zeros are removed if the -Z flag is also set.
This flag has a different meaning when used with -f; see below.
Note that the builtin functions provides the same basic capabilities as typeset -f but gives access to a few extra options; autoload gives further additional options for the case typeset -fu and typeset -fU.
If the POSIX_BUILTINS option is set, the readonly attribute is more restrictive: unset variables can be marked readonly and cannot then be set; furthermore, the readonly attribute cannot be removed from any variable.
It is still possible to change other attributes of the variable though, some of which like -U or -Z would affect the value. More generally, the readonly attribute should not be relied on as a security mechanism.
Note that in zsh (like in pdksh but unlike most other shells) it is still possible to create a local variable of the same name as this is considered a different variable (though this variable, too, can be marked readonly). Special variables that have been made readonly retain their value and readonly attribute when made local.
By default, only soft limits are manipulated. If the -H flag is given use hard limits instead of soft limits. If the -S flag is given together with the -H flag set both hard and soft limits.
If no options are used, the file size limit (-f) is assumed.
If limit is omitted the current value of the specified resources are printed. When more than one resource value is printed, the limit name and unit is printed before each value.
When looping over multiple resources, the shell will abort immediately if it detects a badly formed argument. However, if it fails to set a limit for some other reason it will continue trying to set the remaining limits.
Not all the following resources are supported on all systems. Running ulimit -a will show which are supported.
A resource may also be specified by integer in the form `-N resource', where resource corresponds to the integer defined for the resource by the operating system. This may be used to set the limits for resources known to the shell which do not correspond to option letters. Such limits will be shown by number in the output of `ulimit -a'.
The number may alternatively be out of the range of limits compiled into the shell. The shell will try to read or write the limit anyway, and will report an error if this fails.
The unlimit command is not made available by default when the shell starts in a mode emulating another shell. It can be made available with the command `zmodload -F zsh/rlimits b:unlimit'.
Individual elements of associative array parameters may be unset by using subscript syntax on name, which should be quoted (or the entire command prefixed with noglob) to protect the subscript from filename generation.
If the -m flag is specified the arguments are taken as patterns (should be quoted) and all parameters with matching names are unset. Note that this cannot be used when unsetting associative array elements, as the subscript will be treated as part of the pattern.
The -v flag specifies that name refers to parameters. This is the default behaviour.
unset -f is equivalent to unfunction.
It is possible to wait for recent processes (specified by process ID, not by job) that were running in the background even if the process has exited. Typically the process ID will be recorded by capturing the value of the variable $! immediately after the process has been started. There is a limit on the number of process IDs remembered by the shell; this is given by the value of the system configuration parameter CHILD_MAX. When this limit is reached, older process IDs are discarded, least recently started processes first.
Note there is no protection against the process ID wrapping, i.e. if the wait is not executed soon enough there is a chance the process waited for is the wrong one. A conflict implies both process IDs have been generated by the shell, as other processes are not recorded, and that the user is potentially interested in both, so this problem is intrinsic to process IDs.
If name is not an alias, built-in command, external command, shell function, hashed command, or a reserved word, the exit status shall be non-zero, and -- if -v, -c, or -w was passed -- a message will be written to standard output. (This is different from other shells that write that message to standard error.)
whence is most useful when name is only the last path component of a command, i.e. does not include a `/'; in particular, pattern matching only succeeds if just the non-directory component of the command is passed.
The first form (without the -c, -a or -t options) creates a compiled file. If only the file argument is given, the output file has the name `file.zwc' and will be placed in the same directory as the file. The shell will load the compiled file instead of the normal function file when the function is autoloaded; see the section `Autoloading Functions' in zshmisc(1) for a description of how autoloaded functions are searched. The extension .zwc stands for `zsh word code'.
If there is at least one name argument, all the named files are compiled into the output file given as the first argument. If file does not end in .zwc, this extension is automatically appended. Files containing multiple compiled functions are called `digest' files, and are intended to be used as elements of the FPATH/fpath special array.
The second form, with the -c or -a options, writes the compiled definitions for all the named functions into file. For -c, the names must be functions currently defined in the shell, not those marked for autoloading. Undefined functions that are marked for autoloading may be written by using the -a option, in which case the fpath is searched and the contents of the definition files for those functions, if found, are compiled into file. If both -c and -a are given, names of both defined functions and functions marked for autoloading may be given. In either case, the functions in files written with the -c or -a option will be autoloaded as if the KSH_AUTOLOAD option were unset.
The reason for handling loaded and not-yet-loaded functions with different options is that some definition files for autoloading define multiple functions, including the function with the same name as the file, and, at the end, call that function. In such cases the output of `zcompile -c' does not include the additional functions defined in the file, and any other initialization code in the file is lost. Using `zcompile -a' captures all this extra information.
If the -m option is combined with -c or -a, the names are used as patterns and all functions whose names match one of these patterns will be written. If no name is given, the definitions of all functions currently defined or marked as autoloaded will be written.
Note the second form cannot be used for compiling functions that include redirections as part of the definition rather than within the body of the function; for example
fn1() { { ... } >~/logfile }
can be compiled but
fn1() { ... } >~/logfile
cannot. It is possible to use the first form of zcompile to compile autoloadable functions that include the full function definition instead of just the body of the function.
The third form, with the -t option, examines an existing compiled file. Without further arguments, the names of the original files compiled into it are listed. The first line of output shows the version of the shell which compiled the file and how the file will be used (i.e. by reading it directly or by mapping it into memory). With arguments, nothing is output and the return status is set to zero if definitions for all names were found in the compiled file, and non-zero if the definition for at least one name was not found.
Other options:
When compiling scripts instead of autoloadable functions, it is often desirable to use this option; otherwise the whole file, including the code to define functions which have already been defined, will remain mapped, consequently wasting memory.
These options may also appear as many times as necessary between the listed names to specify the loading style of all following functions, up to the next -k or -z.
The created file always contains two versions of the compiled format, one for big-endian machines and one for small-endian machines. The upshot of this is that the compiled file is machine independent and if it is read or mapped, only one half of the file is actually used (and mapped).
Without arguments the names of all currently loaded binary modules are printed. The -L option causes this list to be in the form of a series of zmodload commands. Forms with arguments are:
The named module is searched for in the same way a command is, using $module_path instead of $path. However, the path search is performed even when the module name contains a `/', which it usually does. There is no way to prevent the path search.
If the module supports features (see below), zmodload tries to enable all features when loading a module. If the module was successfully loaded but not all features could be enabled, zmodload returns status 2.
If the option -s is given, no error is printed if the module was not available (though other errors indicating a problem with the module are printed). The return status indicates if the module was loaded. This is appropriate if the caller considers the module optional.
With -u, zmodload unloads modules. The same name must be given that was given when the module was loaded, but it is not necessary for the module to exist in the file system. The -i option suppresses the error if the module is already unloaded (or was never loaded).
Each module has a boot and a cleanup function. The module will not be loaded if its boot function fails. Similarly a module can only be unloaded if its cleanup function runs successfully.
The standard features are builtins, conditions, parameters and math functions; these are indicated by the prefix `b:', `c:' (`C:' for an infix condition), `p:' and `f:', respectively, followed by the name that the corresponding feature would have in the shell. For example, `b:strftime' indicates a builtin named strftime and p:EPOCHSECONDS indicates a parameter named EPOCHSECONDS. The module may provide other (`abstract') features of its own as indicated by its documentation; these have no prefix.
With -l or -L, features provided by the module are listed. With -l alone, a list of features together with their states is shown, one feature per line. With -L alone, a zmodload -F command that would cause enabled features of the module to be turned on is shown. With -lL, a zmodload -F command that would cause all the features to be set to their current state is shown. If one of these combinations is given with the option -P param then the parameter param is set to an array of features, either features together with their state or (if -L alone is given) enabled features.
With the option -L the module name may be omitted; then a list of all enabled features for all modules providing features is printed in the form of zmodload -F commands. If -l is also given, the state of both enabled and disabled features is output in that form.
A set of features may be provided together with -l or -L and a module name; in that case only the state of those features is considered. Each feature may be preceded by + or - but the character has no effect. If no set of features is provided, all features are considered.
With -e, the command first tests that the module is loaded; if it is not, status 1 is returned. If the module is loaded, the list of features given as an argument is examined. Any feature given with no prefix is simply tested to see if the module provides it; any feature given with a prefix + or - is tested to see if is provided and in the given state. If the tests on all features in the list succeed, status 0 is returned, else status 1.
With -m, each entry in the given list of features is taken as a pattern to be matched against the list of features provided by the module. An initial + or - must be given explicitly. This may not be combined with the -a option as autoloads must be specified explicitly.
With -a, the given list of features is marked for autoload from the specified module, which may not yet be loaded. An optional + may appear before the feature name. If the feature is prefixed with -, any existing autoload is removed. The options -l and -L may be used to list autoloads. Autoloading is specific to individual features; when the module is loaded only the requested feature is enabled. Autoload requests are preserved if the module is subsequently unloaded until an explicit `zmodload -Fa module -feature' is issued. It is not an error to request an autoload for a feature of a module that is already loaded.
When the module is loaded each autoload is checked against the features actually provided by the module; if the feature is not provided the autoload request is deleted. A warning message is output; if the module is being loaded to provide a different feature, and that autoload is successful, there is no effect on the status of the current command. If the module is already loaded at the time when zmodload -Fa is run, an error message is printed and status 1 returned.
zmodload -Fa can be used with the -l, -L, -e and -P options for listing and testing the existence of autoloadable features. In this case -l is ignored if -L is specified. zmodload -FaL with no module name lists autoloads for all modules.
Note that only standard features as described above can be autoloaded; other features require the module to be loaded before enabling.
With -d and one argument, all dependencies for that module are listed. With -d and no arguments, all module dependencies are listed. This listing is by default in a Makefile-like format. The -L option changes this format to a list of zmodload -d commands.
If -d and -u are both used, dependencies are removed. If only one argument is given, all dependencies for that module are removed.
With -ab and no arguments, all autoloaded builtins are listed, with the module name (if different) shown in parentheses after the builtin name. The -L option changes this format to a list of zmodload -a commands.
If -b is used together with the -u option, it removes builtins previously defined with -ab. This is only possible if the builtin is not yet loaded. -i suppresses the error if the builtin is already removed (or never existed).
Autoload requests are retained if the module is subsequently unloaded until an explicit `zmodload -ub builtin' is issued.
If given no condition names, all defined names are listed (as a series of zmodload commands if the -L option is given).
The -uc option removes definitions for autoloaded conditions.
The existence of aliases for modules is completely independent of whether the name resolved is actually loaded as a module: while the alias exists, loading and unloading the module under any alias has exactly the same effect as using the resolved name, and does not affect the connection between the alias and the resolved name which can be removed either by zmodload -R or by redefining the alias. Chains of aliases (i.e. where the first resolved name is itself an alias) are valid so long as these are not circular. As the aliases take the same format as module names, they may include path separators: in this case, there is no requirement for any part of the path named to exist as the alias will be resolved first. For example, `any/old/alias' is always a valid alias.
Dependencies added to aliased modules are actually added to the resolved module; these remain if the alias is removed. It is valid to create an alias whose name is one of the standard shell modules and which resolves to a different module. However, if a module has dependencies, it will not be possible to use the module name as an alias as the module will already be marked as a loadable module in its own right.
Apart from the above, aliases can be used in the zmodload command anywhere module names are required. However, aliases will not be shown in lists of loaded modules with a bare `zmodload'.
Note that zsh makes no distinction between modules that were linked into the shell and modules that are loaded dynamically. In both cases this builtin command has to be used to make available the builtins and other things defined by modules (unless the module is autoloaded on these definitions). This is true even for systems that don't support dynamic loading of modules.
| May 14, 2022 | zsh 5.9 |