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. 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 <[email protected]>. Zsh is now maintained by the members of the zsh-workers mailing list <[email protected]>. The development is currently coordinated by Peter Stephenson <[email protected]>. The coordinator can be contacted at <[email protected]>, but matters relating to the code should generally go to the mailing list.
Zsh is available from the following anonymous FTP sites. These mirror sites are kept frequently up to date. The sites marked with (H) may be mirroring ftp.cs.elte.hu instead of the primary site.
Primary site
ftp://ftp.zsh.org/pub/ http://www.zsh.org/pub/
Australia
ftp://ftp.zsh.org/pub/ http://www.zsh.org/pub/ http://mirror.dejanseo.com.au/pub/zsh/
Hungary
ftp://ftp.cs.elte.hu/pub/zsh/ http://www.cs.elte.hu/pub/zsh/
The up-to-date source code is available via anonymous CVS and Git from Sourceforge. See http://sourceforge.net/projects/zsh/ for details. A summary of instructions for the CVS and Git archives can be found at http://zsh.sourceforget.net/.
Zsh has 3 mailing lists:
Announcements about releases, major changes in the shell and the monthly posting of the Zsh FAQ. (moderated)
User discussions.
Hacking, development, bug reports and patches.
To subscribe or unsubscribe, send mail to the associated administrative address for the mailing list.
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 <[email protected]>. The mailing lists are maintained by Karsten Thygesen <[email protected]>.
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 <[email protected]>, available at http://www.zsh.org/mla/.
Zsh has a list of Frequently Asked Questions (FAQ), maintained by Peter Stephenson <[email protected]>. 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 <[email protected]>.
Zsh has a web page which is located at http://www.zsh.org/. This is maintained by Karsten Thygesen <[email protected]>, of SunSITE Denmark. The contact address for web-related matters is <[email protected]>.
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.
A `wiki' website for zsh has been created at http://www.zshwiki.org/. This is a site which can be added to and modified directly by users without any special permission. You can add your own zsh tips and configurations.
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).
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 PATH, path, MODULE_PATH, module_path, SHELL, HISTFILE, HISTSIZE, GID, EGID, UID, EUID, USERNAME, LD_LIBRARY_PATH, LD_AOUT_LIBRARY_PATH, LD_PRELOAD and LD_AOUT_PRELOAD 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/zsh/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/zsh/zprofile and then $ZDOTDIR/.zprofile. Then, if the shell is interactive, commands are read from /etc/zsh/zshrc and then $ZDOTDIR/.zshrc. Finally, if the shell is a login shell, /etc/zsh/zlogin and $ZDOTDIR/.zlogin are read.
When a login shell exits, the files $ZDOTDIR/.zlogout and then /etc/zsh/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/zsh/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/zsh/zshenv
/etc/zsh/zprofile
/etc/zsh/zshrc
/etc/zsh/zlogin
/etc/zsh/zlogout (installation-specific - /etc is the default)
sh(1), csh(1), tcsh(1), rc(1), bash(1), ksh(1), zshbuiltins(1), zshcompwid(1), zshcompsys(1), zshcompctl(1), zshexpn(1), zshmisc(1), zshmodules(1), zshoptions(1), zshparam(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.