ZSHMISC(1)
NAME
zshmisc - Everything and then some
SYNOPSIS
Everything I haven't put somewhere else
SHELL GRAMMAR
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 com-
mand is its exit status, or 128 plus the signal number if
terminated by a signal.
A pipeline is a sequence of one or more commands separated
by | or |&. |& is shorthand for 2>>&1 |. The standard
output of each command is connected to the standard input
of the next command in the pipeline. 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. The value of a
pipeline is the value of the last command. If a pipeline
is preceded by a !, the value of that pipeline is the log-
ical NOT of the value of the last command.
A sublist is a sequence of one or more pipelines separated
by && or ||. If two pipelines are separated by &&, the
second pipeline is executed only if the first is success-
ful (returns a zero value). If two pipelines are sepa-
rated by ||, the second is executed only if the first is
unsuccessful (returns a nonzero value). Both operators
have equal precedence and are left associative.
A list is a sequence of zero or more sublists separated
by, and optionally terminated by, ;, &, &|, &! or a new-
line. Normally the shell waits for each list to finish
before executing the next one. If a list is terminated by
&, &| or &!, the shell executes it in the background, and
does not wait for it to finish.
PRECOMMAND MODIFIERS
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.
- The command is executed with a - prepended to its
argv[0] string.
noglob Filename generation (globbing) is not performed on
any of the words.
nocorrect
Spelling correction is not done on any of the
words.
exec The command is executed in the parent shell without
forking.
command
The command word is taken to be the name of an
external command, rather than a shell function or
builtin.
COMPLEX COMMANDS
A complex command in zsh is one of the following:
if list then list [ elif list then list ] ... [ else list
] fi
The 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
where term is one ore more newline or ;. 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 parame-
ters instead of the words.
while list do list done
Execute the do list as long as the while list
returns a zero exit status.
until list do list done
Execute the do list as long as until list returns a
nonzero exit status.
repeat word do list done
word is expanded and treated as an arithmetic
expression, which must evaluate to a number n.
list is then executed n times.
case word in [ [(] pattern [ | pattern ] ... ) list ;; ]
... esac
Execute the list associated with the first pattern
that matches word, if any. The form of the pat-
terns is the same as that used for filename genera-
tion. See Filename Generation below.
select name [ in word ... term ] do list done
where term is one ore more newline or ;. 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 parame-
ter 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 selec-
tion until a break or end-of-file is encountered.
( list )
Execute list in a subshell. Traps set by the trap
builtin are reset to their default values while
executing list.
{ list }
Execute list.
function word ... [ () ] [ term ] { list }
word ... () [ term ] { list }
word ... () [ term ] command
where term is one ore more newline or ;. 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 FUNCTIONS below.
time [ pipeline ]
The pipeline is executed, and timing statistics are
reported on the standard error in the form speci-
fied by the TIMEFMT parameter. If pipeline is
omitted, print statistics about the shell process
and its children.
[[ exp ]]
Evaluates the conditional expression exp and return
a zero exit status if it is true. See Conditional
Expressions below for a description of exp.
ALTERNATE FORMS FOR COMPLEX COMMANDS
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 NO_SHORT_LOOPS option is
not set.
if list { list } [ elif list { list } ] ... [ else { list
} ]
An alternate form of if.
if list sublist
A short form of previous one.
for name ( word ... ) sublist
A short form of for.
for name [ in word ... term ] sublist
where term is one ore more newline or ;. Another
short form of for.
foreach name ( word ... ) list end
Another form of for.
while list { list }
An alternative form of while.
until list { list }
An alternative form of until.
repeat word sublist
This is a short form of repeat.
case word { [ [(] pattern [ | pattern ] ... ) list ;; ]
... }
An alternative form of case.
select name [ in word term ] sublist
where term is one ore more newline or ;. A short
form of select.
RESERVED WORDS
The following words are recognized as reserved words when
used as the first word of a command unless quoted or dis-
abled 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.
COMMENTS
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.
ALIASING
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. There-
fore, if an alias is defined for the word foo, alias sub-
stitution 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.
QUOTING
A character may be quoted (that is, made to stand for
itself) by preceding it with a \. \ followed by a newline
is ignored. All characters enclosed between a pair of
single quotes ('') are quoted. A single quote cannot
appear within single quotes. Inside double quotes (""),
parameter and command substitution occurs, and \ quotes
the characters \, `, ", and $.
REDIRECTION
Before a command is executed, its input and output may be
redirected. The following may appear anywhere in a simple
command or may precede or follow a complex command. Sub-
stitution occurs before word or digit is used except as
noted below. If the result of substitution on word pro-
duces more than one filename, redirection occurs for each
separate filename in turn.
<<word Open file word as standard input.
<<>>word Open file word for reading and writing as standard
input. If the file does not exist then it is cre-
ated.
>>word Open file word as standard output. If the file
does not exist then it is created. If the file
exists, and the CLOBBER option is unset, this
causes an error; otherwise, it is truncated to zero
length.
>>| word
>>! word
Same as >>, except that the file is truncated to
zero length if it exists, even if CLOBBER is unset.
>>>>word Open file word as standard output. If the file
exists then output is appended to it. If the file
does not exist, and the CLOBBER option is unset,
this causes an error; otherwise, the file is cre-
ated.
>>>>| word
>>>>! word
Same as >>>>, except that the file is created if it
does not exist, even if CLOBBER is unset.
<<<<[-] word
The shell input is read up to a line that is the
same as word, or to an end-of-file. No parameter
substitution, command substitution or filename gen-
eration is performed on word. The resulting docu-
ment, called a here-document, becomes the standard
input. If any character of word is quoted with
single or double quotes or a \, no interpretation
is placed upon the characters of the document.
Otherwise, parameter and command substitution
occurs, \ followed by a newline is removed, and \
must be used to quote the characters \, $, `, and
the first character of word. If <<- is used, then
all leading tabs are stripped from word and from
the document.
<<<<<<word
Perform shell expansion on word and pass the result
to standard input.
<<&digit
The standard input is duplicated from file descrip-
tor digit (see dup(2)). Similarly for standard
output using >>&digit.
>>&word Same as >>word 2>>&1.
>>>>&word
Same as >>>>word 2>>&1.
<<&- Close the standard input.
>>&- Close the standard output.
<<&p The input from the coprocess is moved to the stan-
dard input.
>>&p The output to the coprocess is moved to the stan-
dard output.
If one of the above is preceded by a digit, then the file
descriptor referred to is that specified by the digit
(instead of the default 0 or 1). The order in which redi-
rections are specified is significant. The shell evalu-
ates each redirection in terms of the (file descriptor,
file) association at the time of evaluation. For example:
... 1>fname 2>&1
first associates file descriptor 1 with file fname. It
then associates file descriptor 2 with the file associated
with file descriptor 1 (that is, fname). If the order of
redirections were reversed, file descriptor 2 would be
associated with the terminal (assuming file descriptor 1
had been) and then file descriptor 1 would be associated
with file fname.
If the user tries to open a file descriptor for writing
more than once, the shell opens the file descriptor as a
pipe to a process that copies its input to all the speci-
fied outputs, similar to tee(1), provided the MULTIOS
option is set. Thus:
date >>foo >>bar
writes the date to two files, named "foo" and "bar". Note
that a pipe is an implicit indirection; thus
date >>foo | cat
writes the date to the file "foo", and also pipes it to
cat.
If the MULTIOS option is set, the word after a redirection
operator is also subjected to filename generation (glob-
bing). Thus
: >> *
will truncate all files in the current directory, assuming
there's at least one. (Without the MULTIOS option, it
would create an empty file called "*".)
If the user tries to open a file descriptor for reading
more than once, the shell opens the file descriptor as a
pipe to a process that copies all the specified inputs to
its output in the order specified, similar to cat(1), pro-
vided the MULTIOS option is set. Thus
sort <<foo <<fubar
or even
sort <<f{oo,ubar}
is equivalent to "cat foo fubar | sort". Similarly, you
can do
echo exit 0 >>>> *.sh
Note that a pipe is in implicit indirection; thus
cat bar | sort <<foo
is equivalent to "cat bar foo | sort" (note the order of
the inputs).
If the MULTIOS option is unset, each redirection replaces
the previous redirection for that file descriptor. How-
ever, all files redirected to are actually opened, so
echo foo >> bar >> baz
when MULTIOS is unset will truncate bar, and write "foo"
into baz.
If a simple command consists of one or more redirection
operators and zero or more parameter assignments, but no
command name, the command cat is assumed. Thus
<< file
prints the contents of file.
If a command is followed by & and job control is not
active, then the default standard input for the command is
the empty file /dev/null. Otherwise, the environment for
the execution of a command contains the file descriptors
of the invoking shell as modified by input/output specifi-
cations.
COMMAND EXECUTION
If a command name contains no slashes, the shell attempts
to locate it. If there exists a shell function by that
name, the function is invoked as described below in FUNC-
TIONS. If there exists a shell builtin by that name, the
builtin is invoked.
Otherwise, the shell searches each element of path for a
directory containing an executable file by that name. If
the search is unsuccessful, the shell prints an error mes-
sage and returns a nonzero exit status.
If execution fails because the file is not in executable
format, and the file is not a directory, it is assumed to
be a shell script. /bin/sh is spawned to execute it. If
the program is a file beginning with #!, the remainder of
the first line specifies an interpreter for the program.
The shell will execute the specified interpreter on oper-
ating systems that do not handle this executable format in
the kernel.
FUNCTIONS
The function reserved word is used to define shell func-
tions. Shell functions are read in and stored internally.
Alias names are resolved when the function is read. Func-
tions are executed like commands with the arguments passed
as positional parameters. (See Execution below).
Functions execute in the same process as the caller and
share all files and present working directory with the
caller. A trap on EXIT set inside a function is executed
after the function completes in the environment of the
caller.
The return builtin is used to return from function calls.
Function identifiers can be listed with the functions
builtin. Functions can be undefined with the unfunction
builtin.
The following functions, if defined, have special meaning
to the shell:
chpwd Executed whenever the current working directory is
changed.
precmd Executed before each prompt.
periodic
If the parameter PERIOD is set, this function is
executed every PERIOD seconds, just before a
prompt.
TRAPxxx
If defined and non-null, this function will be exe-
cuted whenever the shell catches a signal SIGxxx,
where xxx is a signal name as specified for the
kill builtin (see below). The signal number will
be passed as the first parameter to the function.
In addition, TRAPZERR is executed whenever a com-
mand has a non-zero exit status, TRAPDEBUG is exe-
cuted after each command, and TRAPEXIT is executed
when the shell exits, or when the current function
exits if defined inside a function. If a function
of this form is defined and null, the shell and
processes spawned by it will ignore SIGxxx.
JOBS
If the MONITOR option is set, an interactive shell associ-
ates a job with each pipeline. It keeps a table of cur-
rent jobs, printed by the jobs command, and assigns them
small integer numbers. When a job is started asyn-
chronously with &, the shell prints a line which looks
like:
[1] 1234
indicating that the job which was started asynchronously
was job number 1 and had one (top-level) process, whose
process id was 1234.
If a job is started with &| or &!, then that job is imme-
diately disowned. After startup, it does not have a place
in the job table, and is not subject to the job control
features described here.
If you are running a job and wish to do something else you
may hit the key ^Z (control-Z) which sends a TSTP signal
to the current job. The shell will then normally indicate
that the job has been `suspended', and print another
prompt. You can then manipulate the state of this job,
putting it in the background with the bg command, or run
some other commands and then eventually bring the job back
into the foreground with the foreground command fg. A ^Z
takes effect immediately and is like an interrupt in that
pending output and unread input are discarded when it is
typed.
A job being run in the background will suspend if it tries
to read from the terminal. Background jobs are normally
allowed to produce output, but this can be disabled by
giving the command ``stty tostop''. If you set this tty
option, then background jobs will suspend when they try to
produce output like they do when they try to read input.
There are several ways to refer to jobs in the shell. A
job can be referred to by the process id of any process of
the job or by one of the following:
%number
The job with the given number.
%string
Any job whose command line begins with string.
%?string
Any job whose command line contains string.
%% Current job.
%+ Equivalent to %%.
%- Previous job.
The shell learns immediately whenever a process changes
state. It normally informs you whenever a job becomes
blocked so that no further progress is possible. If
notify is not set, it waits until just before it prints a
prompt before it informs you.
When the monitor mode is on, each background job that com-
pletes triggers any trap set for CHLD.
When you try to leave the shell while jobs are running or
suspended, you will be warned that `You have suspended
(running) jobs.' You may use the jobs command to see what
they are. If you do this or immediately try to exit
again, the shell will not warn you a second time; the sus-
pended jobs will be terminated, and the running jobs will
be sent a SIGHUP signal. To avoid having the shell termi-
nate the running jobs, either use the nohup(1) command or
the disown builtin (see below).
SIGNALS
The INT and QUIT signals for an invoked command are
ignored if the command is followed by & and the job
MONITOR option is not active. Otherwise, signals have the
values inherited by the shell from its parent (but see the
TRAPxxx special function above).
ARITHMETIC EVALUATION
An ability to perform integer arithmetic is provided with
the builtin let. Evaluations are performed using long
arithmetic. A leading 0x or 0X denotes hexadecimal. Oth-
erwise, numbers are of the form [base#]n where base is a
decimal number between two and thirty-six representing the
arithmetic base and n is a number in that base (for exam-
ple, `16#ff' is 255 in hexadecimal). If base is omitted
then base 10 is used. For backwards compatibility the
form `[16]ff' is also accepted.
An arithmetic expression uses nearly the same syntax,
precedence, and associativity of expressions in C. The
following operators are supported (listed in decreasing
order of precedence):
+ - ! ~ ++ --
unary plus/minus, logical NOT, complement,
{pre,post}{in,de}crement
<<<< >>>> bitwise shift left, right
& bitwise AND
^ bitwise XOR
| bitwise OR
** exponentiation
* / % multiplication, division, modulus (remain-
der)
+ - addition, subtraction
<< >> <<= >>=
comparison
== != equality and inequality
&& logical AND
|| ^^ logical OR, XOR
? : ternary operator
= += -= *= /= %= &= ^= |= <<<<= >>>>= &&= ||= ^^= **=
assignment
, comma operator
The operators &&, ||, &&=, and ||= are short-circuiting,
and only one of the latter two expressions in a ternary
operator is evaluated. Note the precedence of the bitwise
AND, OR, and XOR operators.
An expression of the form #\x where x is any character
gives the ascii value of this character and an expression
of the form #foo gives the ascii value of the first char-
acter of the value of the parameter foo.
Named parameters and subscripted arrays can be referenced
by name within an arithmetic expression without using the
parameter substitution syntax.
An internal integer representation of a named parameter
can be specified with the integer builtin. Arithmetic
evaluation is performed on the value of each assignment to
a named parameter declared integer in this manner.
Since many of the arithmetic operators require quoting, an
alternative form of the let command is provided. For any
command which begins with a ((, all the characters until a
matching )) are treated as a quoted expression. More pre-
cisely, ((...)) is equivalent to let "...".
CONDITIONAL EXPRESSIONS
A conditional expression is used with the [[ compound com-
mand to test attributes of files and to compare strings.
Each expression can be constructed from one or more of the
following unary or binary expressions:
-a file
true if file exists.
-b file
true if file exists and is a block special file.
-c file
true if file exists and is a character special
file.
-d file
true if file exists and is a directory.
-e file
true if file exists.
-f file
true if file exists and is an ordinary file.
-g file
true if file exists and has its setgid bit set.
-h file
true if file exists and is a symbolic link.
-k file
true if file exists and has its sticky bit set.
-n string
true if length of string is non-zero.
-o option
true if option named option is on. option may be a
single character, in which case it is a single let-
ter option name. (See the SPECIFYING OPTIONS sec-
tion of the zshoptions(1) man page.)
-p file
true if file exists and is a fifo special file or a
pipe.
-r file
true if file exists and is readable by current pro-
cess.
-s file
true if file exists and has size greater than zero.
-t fd true if file descriptor number fd is open and asso-
ciated with a terminal device. (note: fd is not
optional)
-u file
true if file exists and has its setuid bit set.
-w file
true if file exists and is writable by current pro-
cess.
-x file
true if file exists and is executable by current
process. If file exists and is a directory, then
the current process has permission to search in the
directory.
-z string
true if length of string is zero.
-L file
true if file exists and is a symbolic link.
-O file
true if file exists and is owned by the effective
user id of this process.
-G file
true if file exists and its group matches the
effective group id of this process.
-S file
true if file exists and is a socket.
-N file
true if file exists and its access time is not
newer than its modification time.
file1 -nt file2
true if file1 exists and is newer than file2.
file1 -ot file2
true if file1 exists and is older than file2.
file1 -ef file2
true if file1 and file2 exist and refer to the same
file.
string == pattern
string = pattern
true if string matches pattern. The first form is
the preferred one. The other form is for backward
compatibility and should be considered obsolete.
string != pattern
true if string does not match pattern.
string1 << string2
true if string1 comes before string2 based on ASCII
value of their characters.
string1 >> string2
true if string1 comes after string2 based on ASCII
value of their characters.
exp1 -eq exp2
true if exp1 is equal to exp2.
exp1 -ne exp2
true if exp1 is not equal to exp2.
exp1 -lt exp2
true if exp1 is less than exp2.
exp1 -gt exp2
true if exp1 is greater than exp2.
exp1 -le exp2
true if exp1 is less than or equal to exp2.
exp1 -ge exp2
true if exp1 is greater than or equal to exp2.
( exp )
true if exp is true.
! exp true if exp is false.
exp1 && exp2
true if exp1 and exp2 are both true.
exp1 || exp2
true if either exp1 or exp2 is true.
In each of the above expressions, if file is of the form
/dev/fd/n, where n is an integer, then the test applied to
the open file whose descriptor number is n, even if the
underlying system does not support the /dev/fd directory.
COMPATIBILITY
Zsh tries to emulate sh or ksh when it is invoked as sh or
ksh respectively. In this mode the following parameters
are not special and not initialized by the shell: ARGC,
argv, cdpath, fignore, fpath, HISTCHARS, mailpath, MAN-
PATH, manpath, path, prompt, PROMPT, PROMPT2, PROMPT3,
PROMPT4, psvar, status, watch.
The usual zsh starup/shutdown scripts are not executed.
Login shells source /etc/profile followed by $HOME/.pro-
file. If the ENV environment variable is set on invoca-
tion, $ENV is sourced after the profile scripts. The
value of ENV is subjected to parameter expansion, command
substitution, and arithmetic expansion before being inter-
preted as a pathname. Note that the PRIVILEGED option
also affects the execution of startup files. See zshop-
tions(1) for more details.
The following options are set if the shell is invoked as
sh or ksh: NO_BAD_PATTERN, NO_BANG_HIST, NO_BG_NICE,
NO_EQUALS, NO_FUNCTION_ARGZERO, GLOB_SUBST, NO_HUP, INTER-
ACTIVE_COMMENTS, KSH_ARRAYS, NO_MULTIOS, NO_NOMATCH,
RM_STAR_SILENT, POSIX_BUILTINS, SH_FILE_EXPANSION,
SH_GLOB, SH_OPTION_LETTERS, SH_WORD_SPLIT. Additionally
the BSD_ECHO and the IGNORE_BRACES options are set if zsh
is invoked as sh and the KSH_OPTION_PRINT, LOCAL_OPTIONS,
PROMPT_SUBST and SINGLE_LINE_ZLE options are set if zsh is
invoked as ksh.