zshparam - Online in the Cloud

PROGRAM:

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 `!'. A parameter whose name begins with an alphanumeric or underscore is
also referred to as a variable.

The attributes of a parameter determine the type of its value, often referred to as the
parameter type or variable type, and also control other processing that may be applied to
the value when it is referenced. The value type may be a scalar (a string, an integer, or
a floating point number), an array (indexed numerically), or an associative array (an
unordered set of name-value pairs, indexed by name, also referred to as a hash).

Named scalar parameters may have the exported, -x, attribute, to copy them into the
process environment, which is then passed from the shell to any new processes that it
starts. Exported parameters are called environment variables. The shell also imports
environment variables at startup time and automatically marks the corresponding parameters
as exported. Some environment variables are not imported for reasons of security or
because they would interfere with the correct operation of other shell features.

Parameters may also be special, that is, they have a predetermined meaning to the shell.
Special parameters cannot have their type changed or their readonly attribute turned off,
and if a special parameter is unset, then later recreated, the special properties will be
retained.

To declare the type of a parameter, or to assign a string or numeric value to a scalar
parameter, use the typeset builtin.

The value of a scalar parameter may also be assigned by writing:

name=value

In scalar assignment, value is expanded as a single string, in which the elements of
arrays are joined together; filename expansion is not performed unless the option
GLOB_ASSIGN is set.

When the integer attribute, -i, or a floating point attribute, -E or -F, is set for name,
the value is subject to arithmetic evaluation. Furthermore, by replacing `=' with `+=', a
parameter can be incremented or appended to. See the section `Array Parameters' and
Arithmetic Evaluation (in zshmisc(1)) for additional forms of assignment.

Note that assignment may implicitly change the attributes of a parameter. For example,
assigning a number to a variable in arithmetic evaluation may change its type to integer
or float, and with GLOB_ASSIGN assigning a pattern to a variable may change its type to an
array.

To reference the value of a parameter, write `$name' or `${name}'. See Parameter
Expansion in zshexpn(1) for complete details. That section also explains the effect of
the difference between scalar and array assignment on parameter expansion.

ARRAY PARAMETERS

To assign an array value, write one of:

set -A name value ...
name=(value ...)

If no parameter name exists, an ordinary array parameter is created. If the parameter
name exists and is a scalar, it is replaced by a new array. To append to an array without
changing the existing values, use the syntax:

name+=(value ...)

Ordinary array parameters may also be explicitly declared with:

typeset -a name

Associative arrays must be declared before assignment, by using:

typeset -A name

When name refers to an associative array, the list in an assignment is interpreted as
alternating keys and values:

set -A name key value ...
name=(key value ...)

Every key must have a value in this case. Note that this assigns to the entire array,
deleting any elements that do not appear in the list. The append syntax may also be used
with an associative array:

name+=(key value ...)

This adds a new key/value pair if the key is not already present, and replaces the value
for the existing key if it is.

To create an empty array (including associative arrays), use one of:

set -A name
name=()

Array Subscripts
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 in which case
they are numbered from zero.

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 works, as bracketed expressions otherwise are not treated as subscripts.

If the KSH_ARRAYS option is not set, then by default accesses to an array element with a
subscript that evaluates to zero return an empty string, while an attempt to write such an
element is treated as an error. For backward compatibility the KSH_ZERO_SUBSCRIPT option
can be set to cause subscript values 0 and 1 to be equivalent; see the description of the
option in zshoptions(1).

The same subscripting syntax is used for associative arrays, except that no arithmetic
expansion is applied to exp. However, the parsing rules for arithmetic expressions still
apply, which affects the way that certain special characters must be protected from
interpretation. See Subscript Parsing below for details.

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] $foo[2] ..."', whereas `"$foo[@]"' evaluates to `"$foo[1]"
"$foo[2]" ...'. For associative arrays, `[*]' or `[@]' evaluate to all the values, in no
particular order. Note that this does not substitute the keys; see the documentation for
the `k' flag under Parameter Expansion Flags in zshexpn(1) for complete details. When an
array parameter is referenced as `$name' (with no subscript) it evaluates to `$name[*]',
unless the KSH_ARRAYS option is set in which case it evaluates to `${name[0]}' (for an
associative array, this means the value of the key `0', which may not exist even if there
are values for other keys).

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'. Note that some forms of subscripting described below perform
pattern matching, and in that case the substring extends from the start of the match of
the first subscript to the end of the match of the second subscript. For example,

string="abcdefghijklm"
print ${string[(r)d?,(r)h?]}

prints `defghi'. This is an obvious generalisation of the rule for single-character
matches. For a single subscript, only a single character is referenced (not the range of
characters covered by the match).

Note that in substring operations the second subscript is handled differently by the r and
R subscript flags: the former takes the shortest match as the length and the latter the
longest match. Hence in the former case a * at the end is redundant while in the latter
case it matches the whole remainder of the string. This does not affect the result of the
single subscript case as here the length of the match is irrelevant.

Array Element Assignment
A subscript may be used on the left side of an assignment like so:

name[exp]=value

In this form of assignment the element or range specified by exp 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.)

This syntax also works as an argument to the typeset command:

typeset "name[exp]"=value

The value may not be a parenthesized list in this case; only single-element assignments
may be made with typeset. Note that quotes are necessary in this case to prevent the
brackets from being interpreted as filename generation operators. The noglob precommand
modifier could be used instead.

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

unset "name[exp]"

Subscript Flags
If the opening bracket, or the comma in a range, in any subscript expression is directly
followed by an opening parenthesis, the string up to the matching closing one is
considered to be a list of flags, as in `name[(flags)exp]'.

The flags s, n and b take an argument; the delimiter is shown below as `:', but any
character, or the matching pairs `(...)', `{...}', `[...]', or `<...>', may be used, but
note that `<...>' can only be used if the subscript is inside a double quoted expression
or a parameter substitution enclosed in braces as otherwise the expression is interpreted
as a redirection.

The flags currently understood are:

w If the parameter subscripted is a scalar then this flag makes subscripting work on
words instead of characters. The default word separator is whitespace. This flag
may not be used with the i or I flag.

s:string:
This gives the string that separates words (for use with the w flag). The
delimiter character : is arbitrary; see above.

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 then 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 not an associative array. If the parameter is an associative
array, only the value part of each pair is compared to the pattern, and the result
is that value.

If a search through an ordinary array failed, the search sets the subscript to one
past the end of the array, and hence ${array[(r)pattern]} will substitute the empty
string. Thus the success of a search can be tested by using the (i) flag, for
example (assuming the option KSH_ARRAYS is not in effect):

[[ ${array[(i)pattern]} -le ${#array} ]]

If KSH_ARRAYS is in effect, the -le should be replaced by -lt.

R Like `r', but gives the last match. For associative arrays, gives all possible
matches. May be used for assigning to ordinary array elements, but not for
assigning to associative arrays. On failure, for normal arrays this has the effect
of returning the element corresponding to subscript 0; this is empty unless one of
the options KSH_ARRAYS or KSH_ZERO_SUBSCRIPT is in effect.

Note that in subscripts with both `r' and `R' pattern characters are active even if
they were substituted for a parameter (regardless of the setting of GLOB_SUBST
which controls this feature in normal pattern matching). The flag `e' can be added
to inhibit pattern matching. As this flag does not inhibit other forms of
substitution, care is still required; using a parameter to hold the key has the
desired effect:

key2='original key'
print ${array[(Re)$key2]}

i Like `r', but gives the index of the match instead; this may not be combined with a
second argument. On the left side of an assignment, behaves like `r'. For
associative arrays, the key part of each pair is compared to the pattern, and the
first matching key found is the result. On failure substitutes the length of the
array plus one, as discussed under the description of `r', or the empty string for
an associative array.

I Like `i', but gives the index of the last match, or all possible matching keys in
an associative array. On failure substitutes 0, or the empty string for an
associative array. This flag is best when testing for values or keys that do not
exist.

k If used in a subscript on an associative array, this flag causes the keys to be
interpreted as patterns, and returns the value for the first key found where exp is
matched by the key. Note this could be any such key as no ordering of associative
arrays is defined. This flag does not work on the left side of an assignment to an
associative array element. If used on another type of parameter, this behaves like
`r'.

K On an associative array this is like `k' but returns all values where exp is
matched by the keys. On other types of parameters this has the same effect as `R'.

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. The
delimiter character : is arbitrary; see above.

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. The delimiter character : is arbitrary; see above.

e This flag causes any pattern matching that would be performed on the subscript to
use plain string matching instead. Hence `${array[(re)*]}' matches only the array
element whose value is *. Note that other forms of substitution such as parameter
substitution are not inhibited.

This flag can also be used to force * or @ to be interpreted as a single key rather
than as a reference to all values. It may be used for either purpose on the left
side of an assignment.

See Parameter Expansion Flags (zshexpn(1)) for additional ways to manipulate the results
of array subscripting.

Subscript Parsing
This discussion applies mainly to associative array key strings and to patterns used for
reverse subscripting (the `r', `R', `i', etc. flags), but it may also affect parameter
substitutions that appear as part of an arithmetic expression in an ordinary subscript.

To avoid subscript parsing limitations in assignments to associative array elements, use
the append syntax:

aa+=('key with "*strange*" characters' 'value string')

The basic rule to remember when writing a subscript expression is that all text between
the opening `[' and the closing `]' is interpreted as if it were in double quotes (see
zshmisc(1)). However, unlike double quotes which normally cannot nest, subscript
expressions may appear inside double-quoted strings or inside other subscript expressions
(or both!), so the rules have two important differences.

The first difference is that brackets (`[' and `]') must appear as balanced pairs in a
subscript expression unless they are preceded by a backslash (`\'). Therefore, within a
subscript expression (and unlike true double-quoting) the sequence `\[' becomes `[', and
similarly `\]' becomes `]'. This applies even in cases where a backslash is not normally
required; for example, the pattern `[^[]' (to match any character other than an open
bracket) should be written `[^\[]' in a reverse-subscript pattern. However, note that
`\[^\[\]' and even `\[^[]' mean the same thing, because backslashes are always stripped
when they appear before brackets!

The same rule applies to parentheses (`(' and `)') and braces (`{' and `}'): they must
appear either in balanced pairs or preceded by a backslash, and backslashes that protect
parentheses or braces are removed during parsing. This is because parameter expansions
may be surrounded by balanced braces, and subscript flags are introduced by balanced
parentheses.

The second difference is that a double-quote (`"') may appear as part of a subscript
expression without being preceded by a backslash, and therefore that the two characters
`\"' remain as two characters in the subscript (in true double-quoting, `\"' becomes `"').
However, because of the standard shell quoting rules, any double-quotes that appear must
occur in balanced pairs unless preceded by a backslash. This makes it more difficult to
write a subscript expression that contains an odd number of double-quote characters, but
the reason for this difference is so that when a subscript expression appears inside true
double-quotes, one can still write `\"' (rather than `\\\"') for `"'.

To use an odd number of double quotes as a key in an assignment, use the typeset builtin
and an enclosing pair of double quotes; to refer to the value of that key, again use
double quotes:

typeset -A aa
typeset "aa[one\"two\"three\"quotes]"=QQQ
print "$aa[one\"two\"three\"quotes]"

It is important to note that the quoting rules do not change when a parameter expansion
with a subscript is nested inside another subscript expression. That is, it is not
necessary to use additional backslashes within the inner subscript expression; they are
removed only once, from the innermost subscript outwards. Parameters are also expanded
from the innermost subscript first, as each expansion is encountered left to right in the
outer expression.

A further complication arises from a way in which subscript parsing is not different from
double quote parsing. As in true double-quoting, the sequences `\*', and `\@' remain as
two characters when they appear in a subscript expression. To use a literal `*' or `@' as
an associative array key, the `e' flag must be used:

typeset -A aa
aa[(e)*]=star
print $aa[(e)*]

A last detail must be considered when reverse subscripting is performed. Parameters
appearing in the subscript expression are first expanded and then the complete expression
is interpreted as a pattern. This has two effects: first, parameters behave as if
GLOB_SUBST were on (and it cannot be turned off); second, backslashes are interpreted
twice, once when parsing the array subscript and again when parsing the pattern. In a
reverse subscript, it's necessary to use four backslashes to cause a single backslash to
match literally in the pattern. For complex patterns, it is often easiest to assign the
desired pattern to a parameter and then refer to that parameter in the subscript, because
then the backslashes, brackets, parentheses, etc., are seen only when the complete
expression is converted to a pattern. To match the value of a parameter literally in a
reverse subscript, rather than as a pattern, use `${(q)name}' (see zshexpn(1)) to quote
the expanded value.

Note that the `k' and `K' flags are reverse subscripting for an ordinary array, but are
not reverse subscripting for an associative array! (For an associative array, the keys in
the array itself are interpreted as patterns by those flags; the subscript is a plain
string in that case.)

One final note, not directly related to subscripting: the numeric names of positional
parameters (described below) are parsed specially, so for example `$2foo' is equivalent to
`${2}foo'. Therefore, to use subscript syntax to extract a substring from a positional
parameter, the expansion must be surrounded by braces; for example, `${2[3,5]}' evaluates
to the third through fifth characters of the second positional parameter, but `$2[3,5]' is
the entire second parameter concatenated with the filename generation pattern `[3,5]'.

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 parameter `$0' is a special case, see the section `Parameters Set By The
Shell'.

The parameters *, @ and argv are arrays containing all the positional parameters; thus
`$argv[n]', etc., is equivalent to simply `$n'. Note that the options KSH_ARRAYS or
KSH_ZERO_SUBSCRIPT apply to these arrays as well, so with either of those options set,
`${argv[0]}' is equivalent to `$1' and so on.

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

In the parameter lists that follow, the mark `<S>' indicates that the parameter is
special. `<Z>' indicates that the parameter does not exist when the shell initializes in
sh or ksh emulation mode.

The following parameters are automatically set by the shell:

! <S> The process ID of the last command started in the background with &, or put into
the background with the bg builtin.

# <S> The number of positional parameters in decimal. Note that some confusion may occur
with the syntax $#param which substitutes the length of param. Use ${#} to resolve
ambiguities. In particular, the sequence `$#-...' in an arithmetic expression is
interpreted as the length of the parameter -, q.v.

ARGC <S> <Z>
Same as #.

$ <S> The process ID of this shell. Note that this indicates the original shell started
by invoking zsh; all processes forked from the shells without executing a new
program, such as subshells started by (...), substitute the same value.

- <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 status returned by the last command.

0 <S> The name used to invoke the current shell, or as set by the -c command line option
upon invocation. If the FUNCTION_ARGZERO option is set, $0 is set upon entry to a
shell function to the name of the function, and upon entry to a sourced script to
the name of the script, and reset to its previous value when the function or script
returns.

status <S> <Z>
Same as ?.

pipestatus <S> <Z>
An array containing the exit statuses 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)'

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

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)'

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

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. It is also
useful with the zsh/system module which allows the number to be turned into a name
or message.

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)'

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

HISTCMD
The current history event number in an interactive shell, in other words the event
number for the command that caused $HISTCMD to be read. If the current history
event modifies the history, HISTCMD changes to the new maximum history event
number.

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. The value is set to the string returned by the getlogin(3) system call if
that is available.

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. As for $$, the value indicates the
parent of the original shell and does not change in subshells.

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

RANDOM <S>
A pseudo-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.

The values of RANDOM form an intentionally-repeatable pseudo-random sequence;
subshells that reference RANDOM will result in identical pseudo-random values
unless the value of RANDOM is referenced or seeded in the parent shell in between
subshell invocations.

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.

Unlike other special parameters, the type of the SECONDS parameter can be changed
using the typeset command. Only integer and one of the floating point types are
allowed. For example, `typeset -F SECONDS' causes the value to be reported as a
floating point number. The value is available to microsecond accuracy, although
the shell may show more or fewer digits depending on the use of typeset. See the
documentation for the builtin typeset in zshbuiltins(1) for more details.

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

signals
An array containing the names of the signals.

TRY_BLOCK_ERROR <S>
In an always block, indicates whether the preceding list of code caused an error.
The value is 1 to indicate an error, 0 otherwise. It may be reset, clearing the
error condition. See Complex Commands in zshmisc(1)

TRY_BLOCK_INTERRUPT <S>
This variable works in a similar way to TRY_BLOCK_ERROR, but represents the status
of an interrupt from the signal SIGINT, which typically comes from the keyboard
when the user types ^C. If set to 0, any such interrupt will be reset; otherwise,
the interrupt is propagated after the always block.

Note that it is possible that an interrupt arrives during the execution of the
always block; this interrupt is also propagated.

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)'

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

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_eval_context <S> <Z> (ZSH_EVAL_CONTEXT <S>)
An array (colon-separated list) indicating the context of shell code that is being
run. Each time a piece of shell code that is stored within the shell is executed a
string is temporarily appended to the array to indicate the type of operation that
is being performed. Read in order the array gives an indication of the stack of
operations being performed with the most immediate context last.

Note that the variable does not give information on syntactic context such as
pipelines or subshells. Use $ZSH_SUBSHELL to detect subshells.

The context is one of the following:
cmdarg Code specified by the -c option to the command line that invoked the shell.

cmdsubst
Command substitution using the `...` or $(...) construct.

equalsubst
File substitution using the =(...) construct.

eval Code executed by the eval builtin.

evalautofunc
Code executed with the KSH_AUTOLOAD mechanism in order to define an
autoloaded function.

fc Code from the shell history executed by the -e option to the fc builtin.

file Lines of code being read directly from a file, for example by the source
builtin.

filecode
Lines of code being read from a .zwc file instead of directly from the
source file.

globqual
Code executed by the e or + glob qualifier.

globsort
Code executed to order files by the o glob qualifier.

insubst
File substitution using the <(...) construct.

loadautofunc
Code read directly from a file to define an autoloaded function.

outsubst
File substitution using the >(...) construct.

sched Code executed by the sched builtin.

shfunc A shell function.

stty Code passed to stty by the STTY environment variable. Normally this is
passed directly to the system's stty command, so this value is unlikely to
be seen in practice.

style Code executed as part of a style retrieved by the zstyle builtin from the
zsh/zutil module.

toplevel
The highest execution level of a script or interactive shell.

trap Code executed as a trap defined by the trap builtin. Traps defined as
functions have the context shfunc. As traps are asynchronous they may have
a different hierarchy from other code.

zpty Code executed by the zpty builtin from the zsh/zpty module.

zregexparse-guard
Code executed as a guard by the zregexparse command from the zsh/zutil
module.

zregexparse-action
Code executed as an action by the zregexparse command from the zsh/zutil
module.

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

ZSH_PATCHLEVEL
The revision string for the version number of the ChangeLog file in the zsh
distribution. This is most useful in order to keep track of versions of the shell
during development between releases; hence most users should not use it and should
instead rely on $ZSH_VERSION.

zsh_scheduled_events
See the section `The zsh/sched Module' in zshmodules(1).

ZSH_SUBSHELL
Readonly integer. Initially zero, incremented each time the shell forks to create
a subshell for executing code. Hence `(print $ZSH_SUBSHELL)' and `print $(print
$ZSH_SUBSHELL)' output 1, while `( (print $ZSH_SUBSHELL) )' outputs 2.

ZSH_VERSION
The version number of the release of zsh.

PARAMETERS USED BY THE SHELL

The following parameters are used by the shell. Again, `<S>' indicates that the parameter
is special and `<Z>' indicates that the parameter does not exist when the shell
initializes in sh or ksh emulation mode.

In cases where there are two parameters with an upper- and lowercase form of the same
name, such as path and PATH, the lowercase form is an array and the uppercase form is a
scalar with the elements of the array joined together by colons. These are similar to
tied parameters created via `typeset -T'. The normal use for the colon-separated form is
for exporting to the environment, while the array form is easier to manipulate within the
shell. Note that unsetting either of the pair will unset the other; they retain their
special properties when recreated, and recreating one of the pair will recreate the other.

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

BAUD The rate in bits per second at which data reaches the terminal. The line editor
will use this value in order to compensate for a slow terminal by delaying updates
to the display until necessary. If the parameter is unset or the value is zero the
compensation mechanism is turned off. The parameter is not set by default.

This parameter may be profitably set in some circumstances, e.g. for slow modems
dialing into a communications server, or on a slow wide area network. It should be
set to the baud rate of the slowest part of the link for best performance.

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.

CORRECT_IGNORE
If set, is treated as a pattern during spelling correction. Any potential
correction that matches the pattern is ignored. For example, if the value is `_*'
then completion functions (which, by convention, have names beginning with `_')
will never be offered as spelling corrections. The pattern does not apply to the
correction of file names, as applied by the CORRECT_ALL option (so with the example
just given files beginning with `_' in the current directory would still be
completed).

CORRECT_IGNORE_FILE
If set, is treated as a pattern during spelling correction of file names. Any file
name that matches the pattern is never offered as a correction. For example, if
the value is `.*' then dot file names will never be offered as spelling
corrections. This is useful with the CORRECT_ALL option.

DIRSTACKSIZE
The maximum size of the directory stack, by default there is no limit. If the
stack gets larger than this, it will be truncated automatically. This is useful
with the AUTO_PUSHD option.

ENV If the ENV environment variable is set when zsh is invoked as sh or ksh, $ENV is
sourced after the profile scripts. The value of ENV is subjected to parameter
expansion, command substitution, and arithmetic expansion before being interpreted
as a pathname. Note that ENV is not used unless zsh is emulating sh or ksh.

FCEDIT The default editor for the fc builtin. If FCEDIT is not set, the parameter EDITOR
is used; if that is not set either, a builtin default, usually vi, is used.

fignore <S> <Z> (FIGNORE <S>)
An array (colon separated list) containing the suffixes of files to be ignored
during filename completion. However, if completion only generates files with
suffixes in this list, then 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 `#').

The characters must be in the ASCII character set; any attempt to set histchars to
characters with a locale-dependent meaning will be rejected with an error message.

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.

HISTORY_IGNORE
If set, is treated as a pattern at the time history files are written. Any
potential history entry that matches the pattern is skipped. For example, if the
value is `fc *' then commands that invoke the interactive history editor are never
written to the history file.

Note that HISTORY_IGNORE defines a single pattern: to specify alternatives use the
`(first|second|...)' syntax.

Compare the HIST_NO_STORE option or the zshaddhistory hook, either of which would
prevent such commands from being added to the interactive history at all. If you
wish to use HISTORY_IGNORE to stop history being added in the first place, you can
define the following hook:

zshaddhistory() {
emulate -L zsh
## uncomment if HISTORY_IGNORE
## should use EXTENDED_GLOB syntax
# setopt extendedglob
[[ $1 != ${~HISTORY_IGNORE} ]]
}

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.

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

HOME <S>
The default argument for the cd command. This is not set automatically by the
shell in sh, ksh or csh emulation, but it is typically present in the environment
anyway, and if it becomes set it has its usual special behaviour.

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.

If the parameter is unset, the default is used. Note this has a different effect
from setting the parameter to an empty string.

KEYBOARD_HACK
This variable defines a character to be removed from the end of the command line
before interpreting it (interactive shells only). It is intended to fix the problem
with keys placed annoyingly close to return and replaces the SUNKEYBOARDHACK option
which did this for backquotes only. Should the chosen character be one of
singlequote, doublequote or backquote, there must also be an odd number of them on
the command line for the last one to be removed.

For backward compatibility, if the SUNKEYBOARDHACK option is explicitly set, the
value of KEYBOARD_HACK reverts to backquote. If the option is explicitly unset,
this variable is set to empty.

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. If
the MULTIBYTE option is in effect this variable or LANG should contain a value that
reflects the character set in use, even if it is a single-byte character set,
unless only the 7-bit subset (ASCII) is used. For example, if the character set is
ISO-8859-1, a suitable value might be en_US.iso88591 (certain Linux distributions)
or en_US.ISO8859-1 (MacOS).

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.

match
mbegin
mend Arrays set by the shell when the b globbing flag is used in pattern matches. See
the subsection Globbing flags in the documentation for Filename Generation in
zshexpn(1).

MATCH
MBEGIN
MEND Set by the shell when the m globbing flag is used in pattern matches. See the
subsection Globbing flags in the documentation for Filename Generation in
zshexpn(1).

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.

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

prompt <S> <Z>
Same as PS1.

PROMPT_EOL_MARK
When the PROMPT_CR and PROMPT_SP options are set, the PROMPT_EOL_MARK parameter can
be used to customize how the end of partial lines are shown. This parameter
undergoes prompt expansion, with the PROMPT_PERCENT option set. If not set, the
default behavior is equivalent to the value `%B%S%#%s%b'.

PS1 <S>
The primary prompt string, printed before a command is read. It undergoes a
special form of expansion before being displayed; see EXPANSION OF PROMPT SEQUENCES
in zshmisc(1). The default is `%m%# '.

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 `+ '.

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

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.
Output is suppressed for commands executed within the line editor, including
completion; commands explicitly marked with the time keyword still cause the
summary to be printed in this case.

REPLY This parameter is reserved by convention to pass string values between shell
scripts and shell builtins in situations where a function call or redirection are
impossible or undesirable. The read builtin and the select complex command may set
REPLY, and filename generation both sets and examines its value when evaluating
certain expressions. Some modules also employ REPLY for similar purposes.

reply As REPLY, but for array values rather than strings.

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 SINGLE_LINE_ZLE
option is set. It is expanded in the same way as PS1.

RPROMPT2 <S>
RPS2 <S>
This prompt is displayed on the right-hand side of the screen when the secondary
prompt is being displayed on the left. This does not work if the SINGLE_LINE_ZLE
option is set. It is expanded in the same way as PS2.

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

If this is made local, it is not implicitly set to 0, but may be explicitly set
locally.

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. An
assignment to TERM causes zsh to re-initialize the terminal, even if the value does
not change (e.g., `TERM=$TERM'). It is necessary to make such an assignment upon
any change to the terminal definition database or terminal type in order for the
new settings to take effect.

TERMINFO <S>
A reference to a compiled description of the terminal, used by the `terminfo'
library when the system has it; see terminfo(5). If set, this causes the shell to
reinitialise the terminal, making the workaround `TERM=$TERM' unnecessary.

TIMEFMT
The format of process time reports with the time keyword. The default is `%J %U
user %S system %P cpu %*E total'. Recognizes the following escape sequences,
although not all may be available on all systems, and some that are available may
not be useful:

%% 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 100*(%U+%S)/%E.
%W Number of times the process was swapped.
%X The average amount in (shared) text space used in kilobytes.
%D The average amount in (unshared) data/stack space used in kilobytes.
%K The total space used (%X+%D) in kilobytes.
%M The maximum memory the process had in use at any time in megabytes.
%F The number of major page faults (page needed to be brought from disk).
%R The number of minor page faults.
%I The number of input operations.
%O The number of output operations.
%r The number of socket messages received.
%s The number of socket messages sent.
%k The number of signals received.
%w Number of voluntary context switches (waits).
%c Number of involuntary context switches.
%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 of these may be a pattern (be
sure to quote this during the assignment to watch so that it does not immediately
perform file generation); the setting of the EXTENDED_GLOB option is respected.
Any or all of these components may be present in an entry; if a login/logout event
matches all of them, it is reported.

For example, with the EXTENDED_GLOB option set, the following:

watch=('^(pws|barts)')

causes reports for activity assoicated with any user other than pws or barts.

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.

%D{string}
The date formatted as string using the strftime function, with zsh
extensions as described by EXPANSION OF PROMPT SEQUENCES in zshmisc(1).

%(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.

zle_bracketed_paste
Many terminal emulators have a feature that allows applications to identify when
text is pasted into the terminal rather than being typed normally. For ZLE, this
means that special characters such as tabs and newlines can be inserted instead of
invoking editor commands. Furthermore, pasted text forms a single undo event and
if the region is active, pasted text will replace the region.

This two-element array contains the terminal escape sequences for enabling and
disabling the feature. These escape sequences are used to enable bracketed paste
when ZLE is active and disable it at other times. Unsetting the parameter has the
effect of ensuring that bracketed paste remains disabled.

zle_highlight
An array describing contexts in which ZLE should highlight the input text. See
Character Highlighting in zshzle(1).

ZLE_LINE_ABORTED
This parameter is set by the line editor when an error occurs. It contains the
line that was being edited at the point of the error. `print -zr --
$ZLE_LINE_ABORTED' can be used to recover the line. Only the most recent line of
this kind is remembered.

ZLE_REMOVE_SUFFIX_CHARS
ZLE_SPACE_SUFFIX_CHARS
These parameters are used by the line editor. In certain circumstances suffixes
(typically space or slash) added by the completion system will be removed
automatically, either because the next editing command was not an insertable
character, or because the character was marked as requiring the suffix to be
removed.

These variables can contain the sets of characters that will cause the suffix to be
removed. If ZLE_REMOVE_SUFFIX_CHARS is set, those characters will cause the suffix
to be removed; if ZLE_SPACE_SUFFIX_CHARS is set, those characters will cause the
suffix to be removed and replaced by a space.

If ZLE_REMOVE_SUFFIX_CHARS is not set, the default behaviour is equivalent to:

ZLE_REMOVE_SUFFIX_CHARS=$' \t\n;&|'

If ZLE_REMOVE_SUFFIX_CHARS is set but is empty, no characters have this behaviour.
ZLE_SPACE_SUFFIX_CHARS takes precedence, so that the following:

ZLE_SPACE_SUFFIX_CHARS=$'&|'

causes the characters `&' and `|' to remove the suffix but to replace it with a
space.

To illustrate the difference, suppose that the option AUTO_REMOVE_SLASH is in
effect and the directory DIR has just been completed, with an appended /, following
which the user types `&'. The default result is `DIR&'. With
ZLE_REMOVE_SUFFIX_CHARS set but without including `&' the result is `DIR/&'. With
ZLE_SPACE_SUFFIX_CHARS set to include `&' the result is `DIR &'.

Note that certain completions may provide their own suffix removal or replacement
behaviour which overrides the values described here. See the completion system
documentation in zshcompsys(1).

ZLE_RPROMPT_INDENT <S>
If set, used to give the indentation between the right hand side of the right
prompt in the line editor as given by RPS1 or RPROMPT and the right hand side of
the screen. If not set, the value 1 is used.

Typically this will be used to set the value to 0 so that the prompt appears flush
with the right hand side of the screen. This is not the default as many terminals
do not handle this correctly, in particular when the prompt appears at the extreme
bottom right of the screen. Recent virtual terminals are more likely to handle
this case correctly. Some experimentation is necessary.

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