ZSHPARAM(1)

NAME
zshparam - zsh parameters

DESCRIPTION
A parameter has a name, a value, and a number of attributes. A name may be any sequence of alphanumeric characters and underscores, or the single characters `*', `@', `#', `?', `-', `$', or `!'. The value may be a scalar (a string), an integer, an array (indexed numerically), or an associative array (an unordered set of name-value pairs, indexed by name). To assign a scalar or integer value to a parameter, use the typeset builtin. To assign an array value, use `set -A name value ...'. The value of a parameter may also be assigned by writing:

    name=value

If the integer attribute, -i, is set for name, the value is subject to arithmetic evaluation. See the section `Array Parameters' for additional forms of assignment.

In the parameter lists that follow, the mark `<S>' indicates that the parameter is special. Special parameters cannot have their type changed, and they stay special even if unset. `<Z>' indicates that the parameter does not exist when the shell initializes in sh or ksh emulation mode.

ARRAY PARAMETERS
The value of an array parameter may be assigned by writing:

    name=(value ...)

If no parameter name exists, an ordinary array parameter is created. Associative arrays must be declared first, by `typeset -A name'. When name refers to an associative array, the parenthesized list is interpreted as alternating keys and values:

    name=(key value ...)

Every key must have a value in this case. To create an empty array or associative array, use:

    name=()

Individual elements of an array may be selected using a subscript. A subscript of the form `[exp]' selects the single element exp, where exp is an arithmetic expression which will be subject to arithmetic expansion as if it were surrounded by `$((...))'. The elements are numbered beginning with 1 unless the KSH_ARRAYS option is set when they are numbered from zero.

The same subscripting syntax is used for associative arrays, except that no arithmetic expansion is applied to exp.

A subscript of the form `[*]' or `[@]' evaluates to all elements of an array; there is no difference between the two except when they appear within double quotes. `"$foo[*]"' evaluates to `"$foo[1] $foo[2] ..."', while `"$foo[@]"' evaluates to `"$foo[1]" "$foo[2]"', etc.

A subscript of the form `[exp1,exp2]' selects all elements in the range exp1 to exp2, inclusive. (Associative arrays are unordered, and so do not support ranges.) If one of the subscripts evaluates to a negative number, say -n, then the nth element from the end of the array is used. Thus `$foo[-3]' is the third element from the end of the array foo, and `$foo[1,-1]' is the same as `$foo[*]'.

Subscripting may also be performed on non-array values, in which case the subscripts specify a substring to be extracted. For example, if FOO is set to `foobar', then `echo $FOO[2,5]' prints `ooba'.

Subscripts may be used inside braces used to delimit a parameter name, thus `${foo[2]}' is equivalent to `$foo[2]'. If the KSH_ARRAYS option is set, the braced form is the only one that will work, the subscript otherwise not being treated specially.

If a subscript is used on the left side of an assignment the selected element or range is replaced by the expression on the right side. An array (but not an associative array) may be created by assignment to a range or element. Arrays do not nest, so assigning a parenthesized list of values to an element or range changes the number of elements in the array, shifting the other elements to accommodate the new values. (This is not supported for associative arrays.)

To delete an element of an ordinary array, assign `()' to that element. To delete an element of an associative array, use the unset command.

If the opening bracket or the comma is directly followed by an opening parentheses the string up to the matching closing one is considered to be a list of flags. The flags currently understood are:

w   If the parameter subscripted is a scalar than this flag makes subscripting work on words instead of characters. The default word separator is whitespace.

s:string:
    This gives the string that separates words (for use with the w flag).

p   Recognize the same escape sequences as the print builtin in the string argument of a subsequent `s' flag.

f   If the parameter subscripted is a scalar than this flag makes subscripting work on lines instead of characters, i.e. with elements separated by newlines. This is a shorthand for `pws:\n:'.

r   Reverse subscripting: if this flag is given, the exp is taken as a pattern and the result is the first matching array element, substring or word (if the parameter is an array, if it is a scalar, or if it is a scalar and the `w' flag is given, respectively). The subscript used is the number of the matching element, so that pairs of subscripts such as `$foo[(r)??,3]' and `$foo[(r)??,(r)f*]' are possible. If the parameter is an associative array, only the value part of each pair is compared to the pattern.

R   Like `r', but gives the last match. For associative arrays, gives all possible matches.

k   If used in a subscript on a parameter that is not an associative array, this behaves like `r', but if used on an association, it makes the keys be interpreted as patterns and returns the first value whose key matches the exp.

K   On an association this is like `k' but returns all values whose keys match the exp. On other types of parameters this has the same effect as `R'.

i   like `r', but gives the index of the match instead; this may not be combined with a second argument. For associative arrays, the key part of each pair is compared to the pattern, and the first matching key found is used.

I   like `i', but gives the index of the last match, or all possible matching keys in an associative array.

n:expr:
    if combined with `r', `R', `i' or `I', makes them give the nth or nth last match (if expr evaluates to n). This flag is ignored when the array is associative.

b:expr:
    if combined with `r', `R', `i' or `I', makes them begin at the nth or nth last element, word, or character (if expr evaluates to n). This flag is ignored when the array is associative.

e   This option has no effect and retained for backward compatibility only.

POSITIONAL PARAMETERS
The positional parameters provide access to the command-line arguments of a shell function, shell script, or the shell itself; see the section `Invocation', and also the section `Functions'. The parameter n, where n is a number, is the nth positional parameter. The parameters *, @ and argv are arrays containing all the positional parameters; thus `$argv[n]', etc., is equivalent to simply `$n'.

Positional parameters may be changed after the shell or function starts by using the set builtin, by assigning to the argv array, or by direct assignment of the form `n=value' where n is the number of the positional parameter to be changed. This also creates (with empty values) any of the positions from 1 to n that do not already have values. Note that, because the positional parameters form an array, an array assignment of the form `n=(value ...)' is allowed, and has the effect of shifting all the values at positions greater than n by as many positions as necessary to accommodate the new values.

LOCAL PARAMETERS
Shell function executions delimit scopes for shell parameters. (Parameters are dynamically scoped.) The typeset builtin, and its alternative forms declare, integer, local and readonly (but not export), can be used to declare a parameter as being local to the innermost scope.

When a parameter is read or assigned to, the innermost existing parameter of that name is used. (That is, the local parameter hides any less-local parameter.) However, assigning to a non-existent parameter, or declaring a new parameter with export, causes it to be created in the outermost scope.

Local parameters disappear when their scope ends. unset can be used to delete a parameter while it is still in scope; any outer parameter of the same name remains hidden.

Special parameters may also be made local; they retain their special attributes unless either the existing or the newly-created parameter has the -h (hide) attribute. This may have unexpected effects: there is no default value, so if there is no assignment at the point the variable is made local, it will be set to an empty value (or zero in the case of integers). The following:

    typeset PATH=/new/directory:$PATH

is valid for temporarily allowing the shell or programmes called from it to find the programs in /new/directory inside a function.

Note that the restriction in older versions of zsh that local parameters were never exported has been removed.

PARAMETERS SET BY THE SHELL
The following parameters are automatically set by the shell:

! <S>
    The process ID of the last background command invoked.

# <S>
    The number of positional parameters in decimal.

ARGC <S> <Z>
    Same as #.

$ <S>
    The process ID of this shell.

- <S>
    Flags supplied to the shell on invocation or by the set or setopt commands.

* <S>
    An array containing the positional parameters.

argv <S> <Z>
    Same as *. Assigning to argv changes the local positional parameters, but argv is not itself a local parameter. Deleting argv with unset in any function deletes it everywhere, although only the innermost positional parameter array is deleted (so * and @ in other scopes are not affected).

@ <S>
    Same as argv[@], even when argv is not set.

? <S>
    The exit value returned by the last command.

0 <S>
    The name used to invoke the current shell. If the FUNCTION_ARGZERO option is set, this is set temporarily within a shell function to the name of the function, and within a sourced script to the name of the script.

status <S> <Z>
    Same as ?.

pipestatus <S> <Z>
    An array containing the exit values returned by all commands in the last pipeline.

_ <S>
    The last argument of the previous command. Also, this parameter is set in the environment of every command executed to the full pathname of the command.

CPUTYPE
    The machine type (microprocessor class or machine model), as determined at run time.

EGID <S>
    The effective group ID of the shell process. If you have sufficient privileges, you may change the effective group ID of the shell process by assigning to this parameter. Also (assuming sufficient privileges), you may start a single command with a different effective group ID by `(EGID=gid; command)'

EUID <S>
    The effective user ID of the shell process. If you have sufficient privileges, you may change the effective user ID of the shell process by assigning to this parameter. Also (assuming sufficient privileges), you may start a single command with a different effective user ID by `(EUID=uid; command)'

ERRNO <S>
    The value of errno (see errno(3)) as set by the most recently failed system call. This value is system dependent and is intended for debugging purposes.

GID <S>
    The real group ID of the shell process. If you have sufficient privileges, you may change the group ID of the shell process by assigning to this parameter. Also (assuming sufficient privileges), you may start a single command under a different group ID by `(GID=gid; command)'

HOST
    The current hostname.

LINENO <S>
    The line number of the current line within the current script, sourced file, or shell function being executed, whichever was started most recently. Note that in the case of shell functions the line number refers to the function as it appeared in the original definition, not necessarily as displayed by the functions builtin.

LOGNAME
    If the corresponding variable is not set in the environment of the shell, it is initialized to the login name corresponding to the current login session. This parameter is exported by default but this can be disabled using the typeset builtin.

MACHTYPE
    The machine type (microprocessor class or machine model), as determined at compile time.

OLDPWD
    The previous working directory. This is set when the shell initializes and whenever the directory changes.

OPTARG <S>
    The value of the last option argument processed by the getopts command.

OPTIND <S>
    The index of the last option argument processed by the getopts command.

OSTYPE
    The operating system, as determined at compile time.

PPID <S>
    The process ID of the parent of the shell.

PWD The present working directory. This is set when the shell initializes and whenever the directory changes.

RANDOM <S>
    A random integer from 0 to 32767, newly generated each time this parameter is referenced. The random number generator can be seeded by assigning a numeric value to RANDOM.

SECONDS <S>
    The number of seconds since shell invocation. If this parameter is assigned a value, then the value returned upon reference will be the value that was assigned plus the number of seconds since the assignment.

SHLVL <S>
    Incremented by one each time a new shell is started.

signals
    An array containing the names of the signals.

TTY The name of the tty associated with the shell, if any.

TTYIDLE <S>
    The idle time of the tty associated with the shell in seconds or -1 if there is no such tty.

UID <S>
    The real user ID of the shell process. If you have sufficient privileges, you may change the user ID of the shell by assigning to this parameter. Also (assuming sufficient privileges), you may start a single command under a different user ID by `(UID=uid; command)'

USERNAME <S>
    The username corresponding to the real user ID of the shell process. If you have sufficient privileges, you may change the username (and also the user ID and group ID) of the shell by assigning to this parameter. Also (assuming sufficient privileges), you may start a single command under a different username (and user ID and group ID) by `(USERNAME=username; command)'

VENDOR
    The vendor, as determined at compile time.

ZSH_NAME
    Expands to the basename of the command used to invoke this instance of zsh.

ZSH_VERSION
    The version number of this zsh.

PARAMETERS USED BY THE SHELL
The following parameters are used by the shell:

ARGV0
    If exported, its value is used as the argv[0] of external commands. Usually used in constructs like `ARGV0=emacs nethack'.

BAUD
    The baud rate of the current connection. Used by the line editor update mechanism to compensate for a slow terminal by delaying updates until necessary. This may be profitably set to a lower value in some circumstances, e.g. for slow modems dialing into a communications server which is connected to a host via a fast link; in this case, this variable would be set by default to the speed of the fast link, and not the modem. This parameter should be set to the baud rate of the slowest part of the link for best performance. The compensation mechanism can be turned off by setting the variable to zero.

cdpath <S> <Z> (CDPATH <S>)
    An array (colon-separated list) of directories specifying the search path for the cd command.

COLUMNS <S>
    The number of columns for this terminal session. Used for printing select lists and for the line editor.

DIRSTACKSIZE
    The maximum size of the directory stack. If the stack gets larger than this, it will be truncated automatically. This is useful with the AUTO_PUSHD option.

FCEDIT
    The default editor for the fc builtin.

fignore <S> <Z> (FIGNORE <S>)
    An array (colon separated list) containing the suffixes of files to be ignored during filename completion. However, if the completion generates only files which would match if this variable would be ignored, than these files are completed anyway.

fpath <S> <Z> (FPATH <S>)
    An array (colon separated list) of directories specifying the search path for function definitions. This path is searched when a function with the -u attribute is referenced. If an executable file is found, then it is read and executed in the current environment.

histchars <S>
    Three characters used by the shell's history and lexical analysis mechanism. The first character signals the start of a history expansion (default `!'). The second character signals the start of a quick history substitution (default `^'). The third character is the comment character (default `#').

HISTCHARS <S> <Z>
    Same as histchars. (Deprecated.)

HISTFILE
    The file to save the history in when an interactive shell exits. If unset, the history is not saved.

HISTSIZE <S>
    The maximum number of events stored in the internal history list. If you use the HIST_EXPIRE_DUPS_FIRST option, setting this value larger than the SAVEHIST size will give you the difference as a cushion for saving duplicated history events.

HOME <S>
    The default argument for the cd command.

IFS <S>
    Internal field separators (by default space, tab, newline and NUL), that are used to separate words which result from command or parameter expansion and words read by the read builtin. Any characters from the set space, tab and newline that appear in the IFS are called IFS white space. One or more IFS white space characters or one non-IFS white space character together with any adjacent IFS white space character delimit a field. If an IFS white space character appears twice consecutively in the IFS, this character is treated as if it were not an IFS white space character.

KEYTIMEOUT
    The time the shell waits, in hundredths of seconds, for another key to be pressed when reading bound multi-character sequences.

LANG <S>
    This variable determines the locale category for any category not specifically selected via a variable starting with `LC_'.

LC_ALL <S>
    This variable overrides the value of the `LANG' variable and the value of any of the other variables starting with `LC_'.

LC_COLLATE <S>
    This variable determines the locale category for character collation information within ranges in glob brackets and for sorting.

LC_CTYPE <S>
    This variable determines the locale category for character handling functions.

LC_MESSAGES <S>
    This variable determines the language in which messages should be written. Note that zsh does not use message catalogs.

LC_NUMERIC <S>
    This variable affects the decimal point character and thousands separator character for the formatted input/output functions and string conversion functions. Note that zsh ignores this setting when parsing floating point mathematical expressions.

LC_TIME <S>
    This variable determines the locale category for date and time formatting in prompt escape sequences.

LINES <S>
    The number of lines for this terminal session. Used for printing select lists and for the line editor.

LISTMAX
    In the line editor, the number of matches to list without asking first. If the value is negative, the list will be shown if it spans at most as many lines as given by the absolute value. If set to zero, the shell asks only if the top of the listing would scroll off the screen.

LOGCHECK
    The interval in seconds between checks for login/logout activity using the watch parameter.

MAIL
    If this parameter is set and mailpath is not set, the shell looks for mail in the specified file.

MAILCHECK
    The interval in seconds between checks for new mail.

mailpath <S> <Z> (MAILPATH <S>)
    An array (colon-separated list) of filenames to check for new mail. Each filename can be followed by a `?' and a message that will be printed. The message will undergo parameter expansion, command substitution and arithmetic expansion with the variable $_ defined as the name of the file that has changed. The default message is `You have new mail'. If an element is a directory instead of a file the shell will recursively check every file in every subdirectory of the element.

manpath <S> <Z> (MANPATH <S> <Z>)
    An array (colon-separated list) whose value is not used by the shell. The manpath array can be useful, however, since setting it also sets MANPATH, and vice versa.

module_path <S> <Z> (MODULE_PATH <S>)
    An array (colon-separated list) of directories that zmodload searches for dynamically loadable modules. This is initialized to a standard pathname, usually `/usr/local/lib/zsh/$ZSH_VERSION'. (The `/usr/local/lib' part varies from installation to installation.) For security reasons, any value set in the environment when the shell is started will be ignored.

    These parameters only exist if the installation supports dynamic module loading.

NULLCMD <S>
    The command name to assume if a redirection is specified with no command. Defaults to cat. For sh/ksh behavior, change this to :. For csh-like behavior, unset this parameter; the shell will print an error message if null commands are entered.

path <S> <Z> (PATH <S>)
    An array (colon-separated list) of directories to search for commands. When this parameter is set, each directory is scanned and all files found are put in a hash table.

POSTEDIT <S>
    This string is output whenever the line editor exits. It usually contains termcap strings to reset the terminal.

PS1 <S>
    The primary prompt string, printed before a command is read. the default is `%m%# '. It undergoes a special form of expansion before being displayed; see the section `Prompt Expansion'.

PS2 <S>
    The secondary prompt, printed when the shell needs more information to complete a command. It is expanded in the same way as PS1. The default is `%_> ', which displays any shell constructs or quotation marks which are currently being processed.

PS3 <S>
    Selection prompt used within a select loop. It is expanded in the same way as PS1. The default is `?# '.

PS4 <S>
    The execution trace prompt. Default is `+%N:%i> ', which displays the name of the current shell structure and the line number within it. In sh or ksh emulation, the default is `+ '.

PROMPT <S> <Z>
PROMPT2 <S> <Z>
PROMPT3 <S> <Z>
PROMPT4 <S> <Z>
    Same as PS1, PS2, PS3 and PS4, respectively.

psvar <S> <Z> (PSVAR <S>)
    An array (colon-separated list) whose first nine values can be used in PROMPT strings. Setting psvar also sets PSVAR, and vice versa.

prompt <S> <Z>
    Same as PS1.

READNULLCMD <S>
    The command name to assume if a single input redirection is specified with no command. Defaults to more.

REPORTTIME
    If nonnegative, commands whose combined user and system execution times (measured in seconds) are greater than this value have timing statistics printed for them.

RPROMPT <S>
RPS1 <S>
    This prompt is displayed on the right-hand side of the screen when the primary prompt is being displayed on the left. This does not work if the SINGLELINEZLE option is set. It is expanded in the same way as PS1.

SAVEHIST
    The maximum number of history events to save in the history file.

SPROMPT <S>
    The prompt used for spelling correction. The sequence `%R' expands to the string which presumably needs spelling correction, and `%r' expands to the proposed correction. All other prompt escapes are also allowed.

STTY
    If this parameter is set in a command's environment, the shell runs the stty command with the value of this parameter as arguments in order to set up the terminal before executing the command. The modes apply only to the command, and are reset when it finishes or is suspended. If the command is suspended and continued later with the fg or wait builtins it will see the modes specified by STTY, as if it were not suspended. This (intentionally) does not apply if the command is continued via `kill -CONT'. STTY is ignored if the command is run in the background, or if it is in the environment of the shell but not explicitly assigned to in the input line. This avoids running stty at every external command by accidentally exporting it. Also note that STTY should not be used for window size specifications; these will not be local to the command.

TERM <S>
    The type of terminal in use. This is used when looking up termcap sequences.

TIMEFMT
    The format of process time reports with the time keyword. The default is `%E real %U user %S system %P %J'. Recognizes the following escape sequences:

    %%  A `%'.
    %U  CPU seconds spent in user mode.
    %S  CPU seconds spent in kernel mode.
    %E  Elapsed time in seconds.
    %P  The CPU percentage, computed as (%U+%S)/%E.
    %J  The name of this job.

    A star may be inserted between the percent sign and flags printing time. This cause the time to be printed in `hh:mm:ss.ttt' format (hours and minutes are only printed if they are not zero).

TMOUT
    If this parameter is nonzero, the shell will receive an ALRM signal if a command is not entered within the specified number of seconds after issuing a prompt. If there is a trap on SIGALRM, it will be executed and a new alarm is scheduled using the value of the TMOUT parameter after executing the trap. If no trap is set, and the idle time of the terminal is not less than the value of the TMOUT parameter, zsh terminates. Otherwise a new alarm is scheduled to TMOUT seconds after the last keypress.

TMPPREFIX
    A pathname prefix which the shell will use for all temporary files. Note that this should include an initial part for the file name as well as any directory names. The default is `/tmp/zsh'.

watch <S> <Z> (WATCH <S>)
    An array (colon-separated list) of login/logout events to report. If it contains the single word `all', then all login/logout events are reported. If it contains the single word `notme', then all events are reported as with `all' except $USERNAME. An entry in this list may consist of a username, an `@' followed by a remote hostname, and a `%' followed by a line (tty). Any or all of these components may be present in an entry; if a login/logout event matches all of them, it is reported.

WATCHFMT
    The format of login/logout reports if the watch parameter is set. Default is `%n has %a %l from %m'. Recognizes the following escape sequences:

    %n  The name of the user that logged in/out.

    %a  The observed action, i.e. "logged on" or "logged off".

    %l  The line (tty) the user is logged in on.

    %M  The full hostname of the remote host.

    %m  The hostname up to the first `.'. If only the IP address is available or the utmp field contains the name of an X-windows display, the whole name is printed.

        NOTE: The `%m' and `%M' escapes will work only if there is a host name field in the utmp on your machine. Otherwise they are treated as ordinary strings.

    %S (%s)
        Start (stop) standout mode.

    %U (%u)
        Start (stop) underline mode.

    %B (%b)
        Start (stop) boldface mode.

    %t
    %@  The time, in 12-hour, am/pm format.

    %T  The time, in 24-hour format.

    %w  The date in `day-dd' format.

    %W  The date in `mm/dd/yy' format.

    %D  The date in `yy-mm-dd' format.

    %(x:true-text:false-text)
        Specifies a ternary expression. The character following the x is arbitrary; the same character is used to separate the text for the "true" result from that for the "false" result. Both the separator and the right parenthesis may be escaped with a backslash. Ternary expressions may be nested.

        The test character x may be any one of `l', `n', `m' or `M', which indicate a `true' result if the corresponding escape sequence would return a non-empty value; or it may be `a', which indicates a `true' result if the watched user has logged in, or `false' if he has logged out. Other characters evaluate to neither true nor false; the entire expression is omitted in this case.

        If the result is `true', then the true-text is formatted according to the rules above and printed, and the false-text is skipped. If `false', the true-text is skipped and the false-text is formatted and printed. Either or both of the branches may be empty, but both separators must be present in any case.

WORDCHARS <S>
    A list of non-alphanumeric characters considered part of a word by the line editor.

ZBEEP
    If set, this gives a string of characters, which can use all the same codes as the bindkey command as described in the zsh/zle module entry in zshmodules(1), that will be output to the terminal instead of beeping. This may have a visible instead of an audible effect; for example, the string `\e[?5h\e[?5l' on a vt100 or xterm will have the effect of flashing reverse video on and off (if you usually use reverse video, you should use the string `\e[?5l\e[?5h' instead). This takes precedence over the NOBEEP option.

ZDOTDIR
    The directory to search for shell startup files (.zshrc, etc), if not $HOME.