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 `!'. 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 `${name}'. See
Parameter Expansion in zshexpn(1) for complete details. That section
also explains the effect of the difference between scalar and array
assignment on parameter expansion.
ARRAY PARAMETERS
To assign an array value, write one of:
set -A name value ...
name=(value ...)
If no parameter name exists, an ordinary array parameter is created.
If the parameter name exists and is a scalar, it is replaced by a new
array. To append to an array without changing the existing values, use
the syntax:
name+=(value ...)
Within the parentheses on the right hand side of either form of the
assignment, newlines and semicolons are treated the same as white
space, separating individual values. Any consecutive sequence of such
characters has the same effect.
Ordinary array parameters may also be explicitly declared with:
typeset -a name
Associative arrays must be declared before assignment, by using:
typeset -A name
When name refers to an associative array, the list in an assignment is
interpreted as alternating keys and values:
set -A name key value ...
name=(key value ...)
Every key must have a value in this case. Note that this assigns to
the entire array, deleting any elements that do not appear in the list.
The append syntax may also be used with an associative array:
name+=(key value ...)
This adds a new key/value pair if the key is not already present, and
replaces the value for the existing key if it is.
To create an empty array (including associative arrays), use one of:
set -A name
name=()
Array Subscripts
Individual elements of an array may be selected using a subscript. A
subscript of the form `[exp]' selects the single element exp, where exp
is an arithmetic expression which will be subject to arithmetic
expansion as if it were surrounded by `$((...))'. 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. Note that with
the standard zsh numbering of array indices, where the first
element has index 1, the signals are offset by 1 from the signal
number used by the operating system. For example, on typical
Unix-like systems HUP is signal number 1, but is referred to as
$signals[2]. This is because of EXIT at position 1 in the
array, which is used internally by zsh but is not known to the
operating system.
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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