zsh - the Z shell
Because zsh contains many features, the zsh manual has been split into a number
of sections:
- zsh Zsh overview (this section)
- zshroadmap Informal introduction to the manual
- zshmisc Anything not fitting into the other sections
- zshexpn Zsh command and parameter expansion
- zshparam Zsh parameters
- zshoptions Zsh options
- zshbuiltins Zsh built-in functions
- zshzle Zsh command line editing
- zshcompwid Zsh completion widgets
- zshcompsys Zsh completion system
- zshcompctl Zsh completion control
- zshmodules Zsh loadable modules
- zshcalsys Zsh built-in calendar functions
- zshtcpsys Zsh built-in TCP functions
- zshzftpsys Zsh built-in FTP client
- zshcontrib Additional zsh functions and utilities
- zshall Meta-man page containing all of the above
Zsh is a UNIX command interpreter (shell) usable as an interactive login shell
and as a shell script command processor. Of the standard shells, zsh most
closely resembles
ksh but includes many enhancements. It does not
provide compatibility with POSIX or other shells in its default operating
mode: see the section Compatibility below.
Zsh has command line editing, builtin spelling correction, programmable command
completion, shell functions (with autoloading), a history mechanism, and a
host of other features.
Zsh was originally written by Paul Falstad
<pf@zsh.org>. Zsh is now
maintained by the members of the zsh-workers mailing list
<zsh-workers@zsh.org>. The development is currently coordinated
by Peter Stephenson
<pws@zsh.org>. The coordinator can be
contacted at
<coordinator@zsh.org>, but matters relating to the
code should generally go to the mailing list.
Zsh is available from the following HTTP and anonymous FTP site.
ftp://ftp.zsh.org/pub/
https://www.zsh.org/pub/
)
The up-to-date source code is available via Git from Sourceforge. See
https://sourceforge.net/projects/zsh/ for details. A summary of
instructions for the archive can be found at
http://zsh.sourceforge.net/.
Zsh has 3 mailing lists:
- <zsh-announce@zsh.org>
- Announcements about releases, major changes in the shell and the monthly
posting of the Zsh FAQ. (moderated)
- <zsh-users@zsh.org>
- User discussions.
- <zsh-workers@zsh.org>
- Hacking, development, bug reports and patches.
To subscribe or unsubscribe, send mail to the associated administrative address
for the mailing list.
- <zsh-announce-subscribe@zsh.org>
- <zsh-users-subscribe@zsh.org>
- <zsh-workers-subscribe@zsh.org>
- <zsh-announce-unsubscribe@zsh.org>
- <zsh-users-unsubscribe@zsh.org>
- <zsh-workers-unsubscribe@zsh.org>
YOU ONLY NEED TO JOIN ONE OF THE MAILING LISTS AS THEY ARE NESTED. All
submissions to
zsh-announce are automatically forwarded to
zsh-users. All submissions to
zsh-users are automatically
forwarded to
zsh-workers.
If you have problems subscribing/unsubscribing to any of the mailing lists, send
mail to
<listmaster@zsh.org>. The mailing lists are maintained by
Karsten Thygesen
<karthy@kom.auc.dk>.
The mailing lists are archived; the archives can be accessed via the
administrative addresses listed above. There is also a hypertext archive,
maintained by Geoff Wing
<gcw@zsh.org>, available at
https://www.zsh.org/mla/.
Zsh has a list of Frequently Asked Questions (FAQ), maintained by Peter
Stephenson
<pws@zsh.org>. It is regularly posted to the newsgroup
comp.unix.shell and the
zsh-announce mailing list. The latest
version can be found at any of the Zsh FTP sites, or at
http://www.zsh.org/FAQ/. The contact address for FAQ-related matters is
<faqmaster@zsh.org>.
Zsh has a web page which is located at
https://www.zsh.org/. This is
maintained by Karsten Thygesen
<karthy@zsh.org>, of SunSITE
Denmark. The contact address for web-related matters is
<webmaster@zsh.org>.
A userguide is currently in preparation. It is intended to complement the
manual, with explanations and hints on issues where the manual can be
cabbalistic, hierographic, or downright mystifying (for example, the word
`hierographic' does not exist). It can be viewed in its current state at
http://zsh.sourceforge.net/Guide/. At the time of writing, chapters
dealing with startup files and their contents and the new completion system
were essentially complete.
The following flags are interpreted by the shell when invoked to determine where
the shell will read commands from:
- -c
- Take the first argument as a command to execute, rather than reading
commands from a script or standard input. If any further arguments are
given, the first one is assigned to $0, rather than being used as a
positional parameter.
- -i
- Force shell to be interactive. It is still possible to specify a script to
execute.
- -s
- Force shell to read commands from the standard input. If the -s
flag is not present and an argument is given, the first argument is taken
to be the pathname of a script to execute.
If there are any remaining arguments after option processing, and neither of the
options
-c or
-s was supplied, the first argument is taken as
the file name of a script containing shell commands to be executed. If the
option
PATH_SCRIPT is set, and the file name does not contain a
directory path (i.e. there is no `
/' in the name), first the current
directory and then the command path given by the variable
PATH are
searched for the script. If the option is not set or the file name contains a
`
/' it is used directly.
After the first one or two arguments have been appropriated as described above,
the remaining arguments are assigned to the positional parameters.
For further options, which are common to invocation and the
set builtin,
see
zshoptions(1).
The long option `
--emulate' followed (in a separate word) by an
emulation mode may be passed to the shell. The emulation modes are those
described for the
emulate builtin, see
zshbuiltins(1). The `
- -emulate' option must precede any other options (which might
otherwise be overridden), but following options are honoured, so may be used
to modify the requested emulation mode. Note that certain extra steps are
taken to ensure a smooth emulation when this option is used compared with the
emulate command within the shell: for example, variables that conflict
with POSIX usage such as
path are not defined within the shell.
Options may be specified by name using the
-o option.
-o acts like
a single-letter option, but takes a following string as the option name. For
example,
zsh -x -o shwordsplit scr
runs the script
scr, setting the
XTRACE option by the
corresponding letter `
-x' and the
SH_WORD_SPLIT option by name.
Options may be turned
off by name by using
+o instead of
-o.
-o can be stacked up with preceding single-letter options,
so for example `
-xo shwordsplit' or `
-xoshwordsplit' is
equivalent to `
-x -o shwordsplit'.
Options may also be specified by name in GNU long option style, `
-- option-name'. When this is done, `
-' characters
in the option name are permitted: they are translated into `
_', and
thus ignored. So, for example, `
zsh --sh-word-split' invokes
zsh with the
SH_WORD_SPLIT option turned on. Like other option
syntaxes, options can be turned off by replacing the initial `
-' with
a `
+'; thus `
+-sh-word-split' is equivalent to
`
--no-sh-word-split'. Unlike other option syntaxes, GNU-style
long options cannot be stacked with any other options, so for example `
-x-shwordsplit' is an error, rather than being treated like `
-x
- -shwordsplit'.
The special GNU-style option `
--version' is handled; it sends to
standard output the shell's version information, then exits successfully. `
--help' is also handled; it sends to standard output a list of
options that can be used when invoking the shell, then exits successfully.
Option processing may be finished, allowing following arguments that start with
`
-' or `
+' to be treated as normal arguments, in two ways.
Firstly, a lone `
-' (or `
+') as an argument by itself ends
option processing. Secondly, a special option `
--' (or `
+-'), which may be specified on its own (which is the standard POSIX
usage) or may be stacked with preceding options (so `
-x-' is
equivalent to `
-x --'). Options are not permitted to be stacked
after `
--' (so `
-x-f' is an error), but note the
GNU-style option form discussed above, where `
--shwordsplit' is
permitted and does not end option processing.
Except when the
sh/
ksh emulation single-letter options are in
effect, the option `
-b' (or `
+b') ends option processing. `
-b' is like `
--', except that further single-letter
options can be stacked after the `
-b' and will take effect as normal.
Zsh tries to emulate
sh or
ksh when it is invoked as
sh or
ksh respectively; more precisely, it looks at the first letter of the
name by which it was invoked, excluding any initial `
r' (assumed to
stand for `restricted'), and if that is `
b', `
s' or `
k'
it will emulate
sh or
ksh. Furthermore, if invoked as
su
(which happens on certain systems when the shell is executed by the
su
command), the shell will try to find an alternative name from the
SHELL
environment variable and perform emulation based on that.
In
sh and
ksh compatibility modes 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 startup/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.
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_GLOBAL_EXPORT,
NO_HUP,
INTERACTIVE_COMMENTS,
KSH_ARRAYS,
NO_MULTIOS,
NO_NOMATCH,
NO_NOTIFY,
POSIX_BUILTINS,
NO_PROMPT_PERCENT,
RM_STAR_SILENT,
SH_FILE_EXPANSION,
SH_GLOB,
SH_OPTION_LETTERS,
SH_WORD_SPLIT. Additionally the
BSD_ECHO and
IGNORE_BRACES options are set if zsh is invoked as
sh. Also, the
KSH_OPTION_PRINT,
LOCAL_OPTIONS,
PROMPT_BANG,
PROMPT_SUBST and
SINGLE_LINE_ZLE options are set if zsh is
invoked as
ksh.
When the basename of the command used to invoke zsh starts with the letter `
r' or the `
-r' command line option is supplied at invocation,
the shell becomes restricted. Emulation mode is determined after stripping the
letter `
r' from the invocation name. The following are disabled in
restricted mode:
- •
- changing directories with the cd builtin
- •
- changing or unsetting the EGID, EUID, GID,
HISTFILE, HISTSIZE, IFS, LD_AOUT_LIBRARY_PATH,
LD_AOUT_PRELOAD, LD_LIBRARY_PATH, LD_PRELOAD,
MODULE_PATH, module_path, PATH, path,
SHELL, UID and USERNAME parameters
- •
- specifying command names containing /
- •
- specifying command pathnames using hash
- •
- redirecting output to files
- •
- using the exec builtin command to replace the shell with another
command
- •
- using jobs -Z to overwrite the shell process' argument and
environment space
- •
- using the ARGV0 parameter to override argv[0] for external
commands
- •
- turning off restricted mode with set +r or unsetopt
RESTRICTED
These restrictions are enforced after processing the startup files. The startup
files should set up
PATH to point to a directory of commands which can
be safely invoked in the restricted environment. They may also add further
restrictions by disabling selected builtins.
Restricted mode can also be activated any time by setting the
RESTRICTED
option. This immediately enables all the restrictions described above even if
the shell still has not processed all startup files.
Commands are first read from
/etc/zshenv; this cannot be overridden.
Subsequent behaviour is modified by the
RCS and
GLOBAL_RCS
options; the former affects all startup files, while the second only affects
global startup files (those shown here with an path starting with a
/).
If one of the options is unset at any point, any subsequent startup file(s) of
the corresponding type will not be read. It is also possible for a file in
$ZDOTDIR to re-enable
GLOBAL_RCS. Both
RCS and
GLOBAL_RCS are set by default.
Commands are then read from
$ZDOTDIR/.zshenv. If the shell is a login
shell, commands are read from
/etc/zprofile and then
$ZDOTDIR/.zprofile. Then, if the shell is interactive, commands are
read from
/etc/zshrc and then
$ZDOTDIR/.zshrc. Finally, if the
shell is a login shell,
/etc/zlogin and
$ZDOTDIR/.zlogin are
read.
When a login shell exits, the files
$ZDOTDIR/.zlogout and then
/etc/zlogout are read. This happens with either an explicit exit via
the
exit or
logout commands, or an implicit exit by reading
end-of-file from the terminal. However, if the shell terminates due to
exec'ing another process, the logout files are not read. These are also
affected by the
RCS and
GLOBAL_RCS options. Note also that the
RCS option affects the saving of history files, i.e. if
RCS is
unset when the shell exits, no history file will be saved.
If
ZDOTDIR is unset,
HOME is used instead. Files listed above as
being in
/etc may be in another directory, depending on the
installation.
As
/etc/zshenv is run for all instances of zsh, it is important that it
be kept as small as possible. In particular, it is a good idea to put code
that does not need to be run for every single shell behind a test of the form
`
if [[ -o rcs ]]; then ...' so that it will not be executed when zsh
is invoked with the `
-f' option.
Any of these files may be pre-compiled with the
zcompile builtin command
(see
zshbuiltins(1)). If a compiled file exists (named for the original
file plus the
.zwc extension) and it is newer than the original file,
the compiled file will be used instead.
- $ZDOTDIR/.zshenv
- $ZDOTDIR/.zprofile
- $ZDOTDIR/.zshrc
- $ZDOTDIR/.zlogin
- $ZDOTDIR/.zlogout
- ${TMPPREFIX}* (default is /tmp/zsh*)
- /etc/zshenv
- /etc/zprofile
- /etc/zshrc
- /etc/zlogin
- /etc/zlogout (installation-specific - /etc is the
default)
sh(1),
csh(1),
tcsh(1),
rc(1),
bash(1),
ksh(1),
zshall(1),
zshbuiltins(1),
zshcalsys(1),
zshcompwid(1),
zshcompsys(1),
zshcompctl(1),
zshcontrib(1),
zshexpn(1),
zshmisc(1),
zshmodules(1),
zshoptions(1),
zshparam(1),
zshroadmap(1),
zshtcpsys(1),
zshzftpsys(1),
zshzle(1)
IEEE Standard for information Technology - Portable Operating System
Interface (POSIX) - Part 2: Shell and Utilities, IEEE Inc, 1993,
ISBN 1-55937-255-9.