A simple command is a sequence of optional parameter assignments followed by blank-separated words, with optional redirections interspersed. The first word is the command to be executed, and the remaining words, if any, are arguments to the command. If a command name is given, the parameter assignments modify the environment of the command when it is executed. The value of a simple command is its exit status, or 128 plus the signal number if terminated by a signal.
A pipeline is either a simple command, or a sequence of two or more
simple commands where each command is separated from the next by `|'
or `|&'. Where commands are separated by `|', the standard
output of the first command is connected to the
standard input of the next. `|&' is shorthand for `2>&1 |', which
connects both the standard output and the standard error of the
command to the standard input of the next. The value of a pipeline
is the value of the last command, unless the pipeline is preceded by
`!' in which case the value is the logical inverse of the value of the
last command.
If a pipeline is preceded by `coproc', it is executed as a coprocess;
a two-way pipe is established between it and the parent shell. The
shell can read from or write to the coprocess by means of the `>&p'
and `<&p' redirection operators or with `print -p' and `read -p'.
A pipeline cannot be preceded by both `coproc' and `!'.
A sublist is either a single pipeline, or a sequence of two or more
pipelines separated by `&&' or `||'. If two pipelines are separated
by `&&', the second pipeline is executed only if the first succeeds
(returns a zero value). If two pipelines are separated by `||', the
second is executed only if the first fails (returns a nonzero value).
Both operators have equal precedence and are left associative.
The value of the sublist is the value of the last pipeline executed.
A list is a sequence of zero or more sublists, in which each sublist
is terminated by `;', `&', `&|', `&!', or a newline.
This terminator
may optionally be omitted from the last sublist in the list when the
list appears as a complex command inside `(...)'
or `{...}'. When a
sublist is terminated by `;' or newline, the shell waits for it to
finish before executing the next sublist. If a sublist is terminated
by a `&', `&|', or `&!',
the shell executes it in the background, and
does not wait for it to finish.
A backgrounded sublist returns a status of zero.
A simple command may be preceded by a precommand modifier,
which will alter how the command is interpreted. These modifiers are
shell builtin commands with the exception of nocorrect which is
a reserved word.
-
-' prepended to its
argv[0] string.
noglob
nocorrect
exec
command
builtin
A complex command in zsh is one of the following:
if list then list [ elif list then list ] ... [ else list ] fi
if list is executed, and if it returns a zero exit status,
the then list is executed.
Otherwise, the elif list is executed and if its value is zero,
the then list is executed.
If each elif list returns nonzero, the else list is executed.
for name [ in word ... term ] do list done
;.
Expand the list of words, and set the parameter
name to each of them in turn, executing
list each time. If the in word is omitted,
use the positional parameters instead of the words.
for (( [expr1] ; [expr2] ; [expr3] )) do list done
while list do list done
do list as long as the while list
returns a zero exit status.
until list do list done
do list as long as until list
returns a nonzero exit status.
repeat word do list done
case word in [ [(] pattern [ | pattern ] ... ) list (;;|;&) ] ... esac
;& rather than
;;, the following list is also executed. This continues until either
a list is terminated with ;; or the esac is reached.
select name [ in word ... term ] do list done
;.
Print the set of words, each preceded by a number.
If the in word is omitted, use the positional parameters.
The PROMPT3 prompt is printed and a line is read from standard
input. If this line consists of the number of one of the listed
words, then the parameter name
is set to the word corresponding to this number.
If this line is empty, the selection list is printed again.
Otherwise, the value of the parameter name is set to null.
The contents of the line read from standard input is saved
in the parameter REPLY. list is executed
for each selection until a break or end-of-file is encountered.
( list )
trap builtin
are reset to their default values while executing list.
{ list }
function word ... [ () ] [ term ] { list }
() [ term ] { list }
() [ term ] command
;.
Define a function which is referenced by any one of word.
Normally, only one word is provided; multiple words
are usually only useful for setting traps.
The body of the function is the list between
the { and }. See section Functions.
time [ pipeline ]
TIMEFMT parameter.
If pipeline is omitted, print statistics about the
shell process and its children.
[[ exp ]]
Many of zsh's complex commands have alternate forms. These particular
versions of complex commands should be considered deprecated and may be
removed in the future. The versions in the previous section should be
preferred instead. The short versions below only work if sublist
is of the form `{ list }' or if the SHORT_LOOPS
option is set.
if list { list } [ elif list { list } ] ... [ else { list } ]
if.
if list sublist
for name ( word ... ) sublist
for.
for name [ in word ... term ] sublist
;.
Another short form of for.
for (( [expr1] ; [expr2] ; [expr3] )) sublist
for command.
foreach name ( word ... ) list end
for.
while list { list }
while.
until list { list }
until.
repeat word sublist
repeat.
case word { [ [(] pattern [ | pattern ] ... ) list (;;|;&) ] ... }
case.
select name [ in word term ] sublist
;.
A short form of select.
The following words are recognized as reserved words when used as the first
word of a command unless quoted or disabled using disable -r:
do done esac then elif else fi for case
if while function repeat time until
select coproc nocorrect foreach end ! [[ { }
Additionally, `}' is recognized in any position if the IGNORE_BRACES option
is not set.
In noninteractive shells, or in interactive shells with the
INTERACTIVE_COMMENTS option set, a word beginning
with the third character of the histchars parameter
(`#' by default) causes that word and all the following
characters up to a newline to be ignored.
Every token in the shell input is checked to see if there
is an alias defined for it.
If so, it is replaced by the text of the alias if it is in command
position (if it could be the first word of a simple command),
or if the alias is global.
If the text ends with a space, the next word in the shell input
is treated as though it were in command position for purposes of alias
expansion.
An alias is defined using the alias builtin; global aliases
may be defined using the -g option to that builtin.
Alias substitution is done on the shell input before any
other substitution except history substitution. Therefore,
if an alias is defined for the word foo, alias substitution
may be avoided by quoting part of the word, e.g. \foo.
But there is nothing to prevent an alias being defined
for \foo as well.
A character may be quoted (that is, made
to stand for itself) by preceding it with a `\'.
`\' followed by a newline is ignored.
A string enclosed between `$'' and `'' is
processed the same way as the string arguments of the
print builtin, and the resulting string is considered to be
entirely quoted. A literal `'' character can be included in the
string by using the `\'' escape.
All characters enclosed between a pair of single quotes ('') that
is not preceded by a `$' are quoted. A single quote cannot appear
within single quotes.
Inside double quotes (""), parameter and
command substitution occurs, and `\' quotes the characters
`\', ``', `"', and `$'.
Go to the first, previous, next, last section, table of contents.