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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 assign-
ments 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 a sequence of one or more commands separated
by | or |&. |& is shorthand for 2>&1 |. The standard out-
put 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 logical 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 successful
(returns a zero value). If two pipelines are separated by
||, the second is executed only if the first is unsuccessful
(returns a nonzero value). Both operators have equal pre-
cedence and are left associative.
A list is a sequence of zero or more sublists separated by,
and optionally terminated by, ;, &, &|, &! or a newline.
Normally the shell waits for each list to finish before exe-
cuting 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 parameters 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 expres-
sion, 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 patterns is the
same as that used for filename generation. 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 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 )
Execute list in a subshell. Traps set by the trap
builtin are reset to their default values while execut-
ing list.
{ list }
Execute list.
function word ... [ () ] [ term ] { list }
word ... () [ term ] { list }
word ... () [ term ] command
where term is one or more newline or ;. Define a func-
tion 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 func-
tion is the list between the { and }. See FUNCTIONS
below.
If the option SH_GLOB is set for compatibility with
other shells, then whitespace may appear between
between the left and right parentheses when there is a
single word; otherwise, the parentheses will be treated
as forming a globbing pattern in that case.
time [ pipeline ]
The pipeline is executed, and timing statistics are
reported on the standard error in the form specified 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 func-
tion 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 glo-
bal. 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.
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 sin-
gle 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. Substi-
tution occurs before word or digit is used except as noted
below. If the result of substitution on word produces 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 created.
>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; oth-
erwise, 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 created.
>>| 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 substitu-
tion, command substitution or filename generation is
performed on word. The resulting document, 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 descriptor
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 standard
input.
>&p The output to the coprocess is moved to the standard
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
redirections 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 asso-
ciated 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 specified out-
puts, 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), provided the MUL-
TIOS 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. However,
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
copies the contents of file to the standard output.
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 execu-
tion of a command contains the file descriptors of the
invoking shell as modified by input/output specifications.
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 FUNCTIONS. 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 operating
systems that do not handle this executable format in the
kernel.
FUNCTIONS
Shell functions are defined with the function reserved word
or the special syntax "funcname()". The function reserved
word is used to define shell functions. Shell functions are
read in and stored internally. Alias names are resolved
when the function is read. Functions are executed like com-
mands 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 buil-
tin. Functions can be undefined with the unfunction buil-
tin.
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.
preexec
Executed just after a command has been read and is
about to be executed. If the history mechanism is
active, the string to be executed is passed as an argu-
ment.
periodic
If the parameter PERIOD is set, this function is exe-
cuted every PERIOD seconds, just before a prompt.
TRAPxxx
If defined and non-null, this function will be executed
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 command has a non-zero exit status,
TRAPDEBUG is executed 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 current
jobs, printed by the jobs command, and assigns them small
integer numbers. When a job is started asynchronously 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 immedi-
ately 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 immedi-
ately 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 giv-
ing 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 (run-
ning) 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 suspended jobs
will be terminated, and the running jobs will be sent a
SIGHUP signal. To avoid having the shell terminate the run-
ning 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. Other-
wise, 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 example,
`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, pre-
cedence, and associativity of expressions in C. The follow-
ing 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 (remainder)
+ - 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 character 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 evalua-
tion 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 letter
option name. (See the SPECIFYING OPTIONS section 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 process.
-s file
true if file exists and has size greater than zero.
-t fd
true if file descriptor number fd is open and associ-
ated 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 process.
-x file
true if file exists and is executable by current pro-
cess. If file exists and is a directory, then the
current process has permission to search in the direc-
tory.
-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 compati-
bility 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, MANPATH,
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/.profile.
If the ENV environment variable is set on invocation, $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 the PRIVILEGED option also affects the execution
of startup files. See zshoptions(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,
INTERACTIVE_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.
NOTES
Source for zsh is available in the SUNWzshS package.
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