Table of Contents

1. Introducing zsh and how to install it
   1. Sources of information
   2. What is it?
   3. What is it good at?
   4. On what machines will it run?
   5. What's the latest version?
   6. Where do I get it?
   7. I don't have root access: how do I make zsh my login shell?
2. How does zsh differ from...?
   1. Differences from sh and ksh
   2. Similarities with csh
   3. Why do my csh aliases not work? (Plus other alias pitfalls.)
   4. Similarities with tcsh
   5. Similarities with bash
   6. Shouldn't zsh be more/less like ksh/(t)csh?
   7. What is zsh's support for Unicode/UTF-8?
3. How to get various things to work
   1. Why does $var where var="foo bar" not do what I expect?
   2. In which startup file do I put...?
   3. What is the difference between `export' and the ALL_EXPORT option?
   4. How do I turn off spelling correction/globbing for a single command?
   5. How do I get the Meta key to work on my xterm?
   6. How do I automatically display the directory in my xterm title bar?
   7. How do I make the completion list use eight bit characters?
   8. Why do the cursor (arrow) keys not work? (And other terminal oddities.)
   9. Why does my terminal act funny in some way?
   10. Why does zsh not work in an Emacs shell mode any more?
   11. Why do my autoloaded functions not autoload [the first time]?
   12. How does base arithmetic work?
   13. How do I get a newline in my prompt?
   14. Why does bindkey ^a command-name or stty intr ^- do something funny?
   15. Why can't I bind \C-s and \C-q any more?
   16. How do I execute command foo within function foo?
   17. Why do history substitutions with single bangs do something funny?
   18. Why does zsh kill off all my background jobs when I logout?
   19. How do I list all my history entries?
   20. How does the alternative loop syntax, e.g. while {...} {...} work?
   21. Why is my history not being saved?
   22. How do I get a variable's value to be evaluated as another variable?
   23. How do I prevent the prompt overwriting output when there is no newline?
   24. What's wrong with cut and paste on my xterm?
   25. How do I get coloured prompts on my colour xterm?
   26. Why is my output duplicated with `foo 2>&1 >foo.out | bar'?
   27. What are these `^' and `~' pattern characters, anyway?
   28. How do I edit the input buffer in $EDITOR?
   29. Why does `which' output for missing commands go to stdout?
   30. Why doesn't the expansion *.{tex,aux,pdf} do what I expect?
4. The mysteries of completion
   1. What is completion?
   2. What sorts of things can be completed?
   3. How does zsh deal with ambiguous completions?
   4. How do I complete in the middle of words / just what's before the cursor?
   5. How do I get started with programmable completion?
   6. Suppose I want to complete all files during a special completion?
5. Multibyte input and output
   1. What is multibyte input?
   2. How does zsh handle multibyte input and output?
   3. How do I ensure multibyte input and output work on my system?
   4. How can I input characters that aren't on my keyboard?
6. The future of zsh
   1. What bugs are currently known and unfixed? (Plus recent important changes)
   2. Where do I report bugs, get more info / who's working on zsh?

Frequently Asked Questions (FAQ)

This document contains a list of frequently-asked (or otherwise significant) questions concerning the Z-shell, a command interpreter for many UNIX systems which is freely available to anyone with FTP access. Zsh is among the most powerful freely available Bourne-like shell for interactive use.

If you have never heard of sh, csh or ksh, then you are probably better off to start by reading a general introduction to UNIX rather than this document.

If you just want to know how to get your hands on the latest version, skip to question 1.6; if you want to know what to do with insoluble problems, go to 5.2.

Sources of information

Another useful source of information is the collection of FAQ articles posted frequently to the Usenet news groups comp.unix.questions, comp.unix.shells and comp.answers with answers to general questions about UNIX. The fifth of the seven articles deals with shells, including zsh, with a brief description of differences. There is also a separate FAQ on shell differences and how to change your shell. Usenet FAQs are available via FTP from rtfm.mit.edu and mirrors and also on the World Wide Web, including in the USA, UK, and Netherlands.

(As a method of reading the following in Emacs, you can type \M-2 \C-x $ to make all the indented text vanish, then \M-0 \C-x $ when you are on the title you want.)

For any more eclectic information, you should contact the mailing list: see question 5.2.

What is it?

Zsh is a UNIX command interpreter (shell) which of the standard shells most resembles the Korn shell (ksh); its compatibility with the 1988 Korn shell has been gradually increasing. It includes enhancements of many types, notably in the command-line editor, options for customising its behaviour, filename globbing, features to make C-shell (csh) users feel more at home and extra features drawn from tcsh (another `custom' shell).

It was written by Paul Falstad when a student at Princeton; however, Paul doesn't maintain it any more and enquiries should be sent to the mailing list (see question 5.2). Zsh is distributed under a standard Berkeley style copyright.

For more information, the files Doc/intro.txt or Doc/intro.troff included with the source distribution are highly recommended. A list of features is given in FEATURES, also with the source.

What is it good at?

Here are some things that zsh is particularly good at. No claim of exclusivity is made, especially as shells copy one another, though in the areas of command line editing and globbing zsh is well ahead of the competition. I am not aware of a major interactive feature in any other freely-available shell which zsh does not also have (except smallness).

• Command line editing:
  • programmable completion: incorporates the ability to use the full power of zsh's globbing and shell programming features,
  • multi-line commands editable as a single buffer (even files!),
  • variable editing (vared),
  • command buffer stack,
  • print text straight into the buffer for immediate editing (print -z),
  • execution of unbound commands,
  • menu completion in two flavours,
  • variable, editing function and option name completion,
  • inline expansion of variables and history commands.
• Globbing --- extremely powerful, including:
  • recursive globbing (cf. find),
  • file attribute qualifiers (size, type, etc. also cf. find),
  • full alternation and negation of patterns.
• Handling of multiple redirections (simpler than tee).
• Large number of options for tailoring.
• Path expansion (=foo -> /usr/bin/foo).
• Adaptable messages for spelling, watch, time as well as prompt (including conditional expressions).
• Named directories.
• Comprehensive integer and floating point arithmetic.
• Manipulation of arrays (including reverse subscripting).
• Associative arrays (key-to-value hashes)
• Spelling correction.

On what machines will it run?

From version 3.0, zsh uses GNU autoconf as the installation mechanism. This considerably increases flexibility over the old `buildzsh' mechanism. Consequently, zsh should compile and run on any modern version of UNIX, and a great many not-so-modern versions too. The file MACHINES in the distribution has more details.

There used to be separate ports for Windows and OS/2, but these are rather out of date and hard to get; however, zsh exists for the Cygwin environment. See further notes below.

If you need to change something to support a new machine, it would be appreciated if you could add any necessary preprocessor code and alter configure.in and acconfig.h to configure zsh automatically, then send the required context diffs to the list (see question 5.2). Please make sure you have the latest version first.

To get it to work, retrieve the source distribution (see question 1.6), un-gzip it, un-tar it and read the INSTALL file in the top directory. Also read the MACHINES file for up-to-date information on compilation on certain architectures.

Note for users of nawk (The following information comes from Zoltan Hidvegi): On some systems nawk is broken and produces an incorrect signames.h file. This makes the signals code unusable. This often happens on Ultrix, HP-UX, IRIX (?). Install gawk if you experience such problems.

What's the latest version?

Zsh 5.8 is the latest production version. For details of all the changes, see the NEWS file in the source distribution.

A beta of the next version is sometimes available. Development of zsh is patch by patch, with each intermediate version publicly available. Note that this `open' development system does mean bugs are sometimes introduced into the most recent archived version. These are usually fixed quickly. If you are really interested in getting the latest improvements, and less worried about providing a stable environment, development versions are uploaded quite frequently to the archive in the development subdirectory.

Note also that as the shell changes, it may become incompatible with older versions; see the end of question 5.1 for a partial list. Changes of this kind are almost always forced by an awkward or unnecessary feature in the original design (as perceived by current users), or to enhance compatibility with other Bourne shell derivatives, or (mostly in the 3.0 series) to provide POSIX compliancy.

Where do I get it?

The coordinator of development is currently me; the alias coordinator@zsh.org can be used to contact whoever is in the hot seat. https://www.zsh.org/ is the official archive site, currently in Australia. Test versions are kept in the `testing' subdirectory: such up-to-the-minute development versions should only be retrieved if you actually plan to help test the latest version of the shell.

A Windows port was created by Amol Deshpandem based on 3.0.5 (which is now rather old). This has now been restored and can be found at https://zsh-nt.sourceforge.net/.

All recent releases of zsh compile under Cygwin, a freely available UNIX-style environment for the Win32 API, and a pre-compiled version of zsh can be downloaded by the Cygwin installer. You can find information about this at https://www.cygwin.com/. Please email zsh-workers@zsh.org if you have information about other ports.

I don't have root access: how do I make zsh my login shell?

Unfortunately, on many machines you can't use chsh to change your shell unless the name of the shell is contained in /etc/shells, so if you have your own copy of zsh you need some sleight-of-hand to use it when you log on. (Simply typing zsh is not really a solution since you still have your original login shell waiting for when you exit.)

The basic idea is to use exec <zsh-path> to replace the current shell with zsh. Often you can do this in a login file such as .profile (if your shell is sh or ksh) or .login (if it's csh). Make sure you have some way of altering the file (e.g. via FTP) before you try this as exec is often rather unforgiving.

If you have zsh in a subdirectory bin of your home directory, put this in .profile:

    [ -f $HOME/bin/zsh ] && exec $HOME/bin/zsh -l

    if ( -f ~/bin/zsh ) exec ~/bin/zsh -l

If you want to check this works before committing yourself to it, you can make the login shell ask whether to exec zsh. The following work for Bourne-like shells:

    [ -f $HOME/bin/zsh ] && {
            echo "Type Y to run zsh: \c"
            read line
            [ "$line" = Y ] && exec $HOME/bin/zsh -l
    }

    if ( -f ~/bin/zsh ) then
            echo -n "Type Y to run zsh: "
            if ( "$<" == Y ) exec ~/bin/zsh -l
    endif

It's not a good idea to put this (even without the -l) into .cshrc, at least without some tests on what the csh is supposed to be doing, as that will cause _every_ instance of csh to turn into a zsh and will cause csh scripts (yes, unfortunately some people write these) which do not call `csh -f' to fail. If you want to tell xterm to run zsh, change the SHELL environment variable to the full path of zsh at the same time as you exec zsh (in fact, this is sensible for consistency even if you aren't using xterm). If you have to exec zsh from your .cshrc, a minimum safety check is if ($?prompt) exec zsh.

If you like your login shell to appear in the process list as -zsh, you can link zsh to -zsh (e.g. by ln -s ~/bin/zsh ~/bin/-zsh) and change the exec to exec -zsh. (Make sure -zsh is in your path.) This has the same effect as the -l option.

Footnote: if you DO have root access, make sure zsh goes in /etc/shells on all appropriate machines, including NIS clients, or you may have problems with FTP to that machine.

How does zsh differ from...?

As has already been mentioned, zsh is most similar to ksh, while many of the additions are to please csh users. Here are some more detailed notes. See also the article `UNIX shell differences and how to change your shell' posted frequently to the USENET group comp.unix.shell.

Differences from sh and ksh

Most features of ksh (and hence also of sh) are implemented in zsh; problems can arise because the implementation is slightly different. Note also that not all ksh's are the same either. I have based this on the 11/16/88f version of ksh; differences from ksh93 will be more substantial.

As a summary of the status:

1. because of all the options it is not safe to assume a general zsh run by a user will behave as if sh or ksh compatible;
2. invoking zsh as sh or ksh (or if either is a symbolic link to zsh) sets appropriate options and improves compatibility (from within zsh itself, calling ARGV0=sh zsh will also work);
3. from version 3.0 onward the degree of compatibility with sh under these circumstances is very high: zsh can now be used with GNU configure or perl's Configure, for example;
4. the degree of compatibility with ksh is also high, but a few things are missing: for example the more sophisticated pattern-matching expressions are different for versions before 3.1.3 --- see the detailed list below;
5. also from 3.0, the command `emulate' is available: `emulate ksh' and `emulate sh' set various options as well as changing the effect of single-letter option flags as if the shell had been invoked with the appropriate name. Including the command `emulate sh; setopt localoptions' in a shell function will turn on sh emulation for that function only. In version 4 (and in 3.0.6 through 8), this can be abbreviated as `emulate -L sh'.

The classic difference is word splitting, discussed in question 3.1; this catches out very many beginning zsh users. As explained there, this is actually a bug in every other shell. The answer is to set SH_WORD_SPLIT for backward compatibility. The next most classic difference is that unmatched glob patterns cause the command to abort; set NO_NOMATCH for those.

Here is a list of various options which will increase ksh compatibility, though maybe decrease zsh's abilities: see the manual entries for GLOB_SUBST, IGNORE_BRACES (though brace expansion occurs in some versions of ksh), KSH_ARRAYS, KSH_GLOB, KSH_OPTION_PRINT, LOCAL_OPTIONS, NO_BAD_PATTERN, NO_BANG_HIST, NO_EQUALS, NO_HUP, NO_NOMATCH, NO_RCS, NO_SHORT_LOOPS, PROMPT_SUBST, RM_STAR_SILENT, POSIX_ALIASES, POSIX_BUILTINS, POSIX_IDENTIFIERS, SH_FILE_EXPANSION, SH_GLOB, SH_OPTION_LETTERS, SH_WORD_SPLIT (see question 3.1) and SINGLE_LINE_ZLE. Note that you can also disable any built-in commands which get in your way. If invoked as `ksh', the shell will try to set suitable options.

Here are some differences from ksh which might prove significant for ksh programmers, some of which may be interpreted as bugs; there must be more. Note that this list is deliberately rather full and that most of the items are fairly minor. Those marked `*' perform in a ksh-like manner if the shell is invoked with the name `ksh', or if `emulate ksh' is in effect. Capitalised words with underlines refer to shell options.

• Syntax:
  • * Shell word splitting: see question 3.1.
  • * Arrays are (by default) more csh-like than ksh-like: subscripts start at 1, not 0; array[0] refers to array[1]; $array refers to the whole array, not $array[0]; braces are unnecessary: $a[1] == ${a[1]}, etc. Set the KSH_ARRAYS option for compatibility.
  • Furthermore, individual elements of arrays in zsh are always strings, not separate parameters. This means, for example, you can't `unset' an array element in zsh as you can in ksh; you can only set it to the empty string, or shorten the array. (You can unset elements of associative arrays in zsh because those are a completely different type of object.)
  • Coprocesses are established by coproc; |& behaves like csh. Handling of coprocess file descriptors is also different.
  • In cmd1 && cmd2 &, only cmd2 instead of the whole expression is run in the background in zsh. The manual implies this is a bug. Use { cmd1 && cmd2 } & as a workaround.
• Command line substitutions, globbing etc.:
  • * Failure to match a globbing pattern causes an error (use NO_NOMATCH).
  • * The results of parameter substitutions are treated as plain text: foo="*"; print $foo prints all files in ksh but * in zsh (use GLOB_SUBST).
  • * $PSn do not do parameter substitution by default (use PROMPT_SUBST).
  • * Standard globbing does not allow ksh-style `pattern-lists'. Equivalents:

    
    ----------------------------------------------------------------------
          ksh              zsh         Meaning
         ------           ------       ---------
         !(foo)            ^foo        Anything but foo.
                    or   foo1~foo2     Anything matching foo1 but foo2[1].
    @(foo1|foo2|...)  (foo1|foo2|...)  One of foo1 or foo2 or ...
         ?(foo)           (foo|)       Zero or one occurrences of foo.
         *(foo)           (foo)#       Zero or more occurrences of foo.
         +(foo)           (foo)##      One or more occurrences of foo.
    ----------------------------------------------------------------------
    
    

    The ^, ~ and # (but not |)forms require EXTENDED_GLOB. From version 3.1.3, the ksh forms are fully supported when the option KSH_GLOB is in effect; for previous versions you must use the table above.

    [1] See question 3.27 for more on the mysteries of ~ and ^.

  • Unquoted assignments do file expansion after :s (intended for PATHs).
  • * typeset and integer have special behaviour for assignments in ksh, but not in zsh. For example, this doesn't work in zsh:

    
              integer k=$(wc -l ~/.zshrc)
    
    

    because the return value from wc includes leading whitespace which causes wordsplitting. Ksh handles the assignment specially as a single word.
• Command execution:
  • * There is no $ENV variable (use /etc/zshrc, ~/.zshrc; note also $ZDOTDIR).
  • * $PATH is not searched for commands specified at invocation without -c.
• Aliases and functions:
  • The order in which aliases and functions are defined is significant: function definitions with () expand aliases -- see question 2.3.
  • Aliases and functions cannot be exported.
  • There are no tracked aliases: command hashing replaces these.
  • The use of aliases for key bindings is replaced by `bindkey'.
  • * Options are not local to functions (use LOCAL_OPTIONS; note this may always be unset locally to propagate options settings from a function to the calling level).
  • Functions defined with `function funcname { body }' behave the same way as those defined with `funcname () { body }'. In ksh, the former behave as if the body were read from a file with `.', and only the latter behave as true functions.
• Traps and signals:
  • * Traps are not local to functions. The option LOCAL_TRAPS is available from 3.1.6.
  • TRAPERR has become TRAPZERR (this was forced by UNICOS which has SIGERR).
• Editing:
  • The options gmacs, viraw are not supported. Use bindkey to change the editing behaviour: set -o {emacs,vi} becomes `bindkey -{e,v}', although `set -o emacs' and `set -o vi' are supported for compatibility; for gmacs, go to emacs mode and use `bindkey \^t gosmacs-transpose-characters'.
  • The keyword option does not exist and -k is instead interactivecomments. (keyword is not in recent versions of ksh either.)
  • * Management of histories in multiple shells is different: the history list is not saved and restored after each command. The option SHARE_HISTORY appeared in 3.1.6 and is set in ksh compatibility mode to remedy this.
  • \ does not escape editing chars (use ^V).
  • Not all ksh bindings are set (e.g. <ESC>#; try <ESC>q).
  • * # in an interactive shell is not treated as a comment by default.
  • In vi command mode the keys "k" and "j" move the cursor to the end of the line. To move the cursor to the start instead, use

    
              bindkey -M vicmd 'k' vi-up-line-or-history
              bindkey -M vicmd 'j' vi-down-line-or-history
    
    

• Built-in commands:
  • Some built-ins (r, autoload, history, integer ...) were aliases in ksh.
  • There is no built-in command newgrp: use e.g. alias newgrp="exec newgrp"
  • jobs has no -n flag.
• Other idiosyncrasies:
  • select always redisplays the list of selections on each loop.

Similarities with csh

Although certain features aim to ease the withdrawal symptoms of csh (ab)users, the syntax is in general rather different and you should certainly not try to run scripts without modification. The c2z script is provided with the source (in Misc/c2z) to help convert .cshrc and .login files; see also the next question concerning aliases, particularly those with arguments.

Csh-compatibility additions include:

• logout, rehash, source, (un)limit built-in commands.
• *rc file for interactive shells.
• Directory stacks.
• cshjunkie*, ignoreeof options.
• The CSH_NULL_GLOB option.
• >&, |& etc. redirection. (Note that >file 2>&1 is the standard Bourne shell command for csh's >&file.)
• foreach ... loops; alternative syntax for other loops.
• Alternative syntax if ( ... ) ..., though this still doesn't work like csh: it expects a command in the parentheses. Also for, which.
• $PROMPT as well as $PS1, $status as well as $?, $#argv as well as $#, ....
• Escape sequences via % for prompts.
• Special array variables $PATH etc. are colon-separated, $path are arrays.
• !-type history (which may be turned off via setopt nobanghist).
• Arrays have csh-like features (see under 2.1).

Why do my csh aliases not work? (Plus other alias pitfalls.)

First of all, check you are using the syntax

    alias newcmd='list of commands'

    alias newcmd 'list of commands'

Otherwise, your aliases probably contain references to the command line of the form \!*, etc. Zsh does not handle this behaviour as it has shell functions which provide a way of solving this problem more consistent with other forms of argument handling. For example, the csh alias

    alias cd 'cd \!*; echo $cwd'

    cd() { builtin cd "$@"; echo $PWD; }

    cd() { builtin cd "$@"; print -D $PWD; }

Here is Bart Schaefer's guide to converting csh aliases for zsh.

1. If the csh alias references "parameters" (\!:1, \!* etc.), then in zsh you need a function (referencing $1, $* etc.). Otherwise, you can use a zsh alias.
2. If you use a zsh function, you need to refer _at_least_ to $* in the body (inside the { }). Parameters don't magically appear inside the { } the way they get appended to an alias.
3. If the csh alias references its own name (alias rm "rm -i"), then in a zsh function you need the "command" or "builtin" keyword (function rm() { command rm -i "$@" }), but in a zsh alias you don't (alias rm="rm -i").
4. If you have aliases that refer to each other (alias ls "ls -C"; alias lf "ls -F" ==> lf == ls -C -F) then you must either:
   • convert all of them to zsh functions; or
   • after converting, be sure your .zshrc defines all of your aliases before it defines any of your functions.

Remember that it is NOT a syntax error in a zsh function to refer to a position ($1, $2, etc.) greater than the number of parameters. (E.g., in a csh alias, a reference to \!:5 will cause an error if 4 or fewer arguments are given; in a zsh function, $5 is the empty string if there are 4 or fewer parameters.)

To begin a zsh alias with a - (dash, hyphen) character, use alias --:

             csh                            zsh
        ===============             ==================
        alias - "fg %-"             alias -- -="fg %-"

Stay away from alias -g in zsh until you REALLY know what you're doing.

There is one other serious problem with aliases: consider

    alias l='/bin/ls -F'
    l() { /bin/ls -la "$@" | more }

One workaround for this is to use the "function" keyword instead:

    alias l='/bin/ls -F'
    function l { /bin/ls -la "$@" | more }

You need to be careful if you are defining a function with multiple names; most people don't need to do this, so it's an unusual problem, but in case you do you should be aware that in versions of the shell before 5.1 names after the first were expanded:

    function a b c { ... }

The rest of this item assumes you use the (more common, but equivalent) LPAR()RPAR() definitions.

Bart Schaefer's rule is: Define first those aliases you expect to use in the body of a function, but define the function first if the alias has the same name as the function.

If you aware of the problem, you can always escape part or all of the name of the function:

     'l'() { /bin/ls -la "$@" | more }

Similarities with tcsh

(The sections on csh apply too, of course.) Certain features have been borrowed from tcsh, including $watch, run-help, $savehist, periodic commands etc., extended prompts, sched and which built-ins. Programmable completion was inspired by, but is entirely different to, tcsh's complete. (There is a perl script called lete2ctl in the Misc directory of the source distribution to convert complete to compctl statements.) This list is not definitive: some features have gone in the other direction.

If you're missing the editor function run-fg-editor, try something with bindkey -s (which binds a string to a keystroke), e.g.

    bindkey -s '^z' '\eqfg %$EDITOR:t\n'

    bindkey -s '^p' '\eqpwd\n'

    bindkey '\eq' push-input

    run-fg-editor() {
      zle push-input
      BUFFER="fg %$EDITOR:t"
      zle accept-line
    }
    zle -N run-fg-editor

Similarities with bash

The Bourne-Again Shell, bash, is another enhanced Bourne-like shell; the most obvious difference from zsh is that it does not attempt to emulate the Korn shell. Since both shells are under active development it is probably not sensible to be too specific here. Broadly, bash has paid more attention to standards compliancy (i.e. POSIX) for longer, and has so far avoided the more abstruse interactive features (programmable completion, etc.) that zsh has.

In recent years there has been a certain amount of crossover in the extensions, however. Zsh (as of 3.1.6) has bash's `${var/old/new}' feature for replacing the text old with the text new in the parameter $var. Note one difference here: while both shells implement the syntax `${var/#old/new}' and `${var/%old/new}' for anchoring the match of old to the start or end of the parameter text, respectively, in zsh you can't put the `#' or `%' inside a parameter: in other words `{var/$old/new}' where old begins with a `#' treats that as an ordinary character in zsh, unlike bash. To do this sort of thing in zsh you can use (from 3.1.7) the new syntax for anchors in any pattern, `(#s)' to match the start of a string, and `(#e)' to match the end. These require the option EXTENDED_GLOB to be set.

Shouldn't zsh be more/less like ksh/(t)csh?

People often ask why zsh has all these `unnecessary' csh-like features, or alternatively why zsh doesn't understand more csh syntax. This is far from a definitive answer and the debate will no doubt continue.

Paul's object in writing zsh was to produce a ksh-like shell which would have features familiar to csh users. For a long time, csh was the preferred interactive shell and there is a strong resistance to changing to something unfamiliar, hence the additional syntax and CSH_JUNKIE options. This argument still holds. On the other hand, the arguments for having what is close to a plug-in replacement for ksh are, if anything, even more powerful: the deficiencies of csh as a programming language are well known (look in any Usenet FAQ archive, e.g. https://www.cis.ohio-state.edu/hypertext/faq/usenet/unix-faq/\ shell/csh-whynot/faq.html if you are in any doubt) and zsh is able to run many standard scripts such as /etc/rc.

Of course, this makes zsh rather large and feature-ridden so that it seems to appeal mainly to hackers. The only answer, perhaps not entirely satisfactory, is that you have to ignore the bits you don't want. The introduction of loadable in modules in version 3.1 should help.

What is zsh's support for Unicode/UTF-8?

`Unicode', or UCS for Universal Character Set, is the modern way of specifying character sets. It replaces a large number of ad hoc ways of supporting character sets beyond ASCII. `UTF-8' is an encoding of Unicode that is particularly natural on Unix-like systems.

The production branch of zsh, 4.2, has very limited support: the built-in printf command supports "\u" and "\U" escapes to output arbitrary Unicode characters; ZLE (the Zsh Line Editor) has no concept of character encodings, and is confused by multi-octet encodings.

However, the 4.3 branch has much better support, and furthermore this is now fairly stable. (Only a few minor areas need fixing before this becomes a production release.) This is discussed more fully below, see `Multibyte input and output'.

How to get various things to work

Why does $var where var="foo bar" not do what I expect?

In most Bourne-shell derivatives, multiple-word variables such as

    var="foo bar"

For example, defining the function args to show the number of its arguments:

    args() { echo $#; }

    args $var

    setopt shwordsplit

Unless you need strict sh/ksh compatibility, you should ask yourself whether you really want this behaviour, as it can produce unexpected effects for variables with entirely innocuous embedded spaces. This can cause horrendous quoting problems when invoking scripts from other shells. The natural way to produce word-splitting behaviour in zsh is via arrays. For example,

    set -A array one two three twenty

    array=(one two three twenty)

    args $array

Note that this happens regardless of the value of the internal field separator, $IFS; in other words, with IFS=:; foo=a:b; args $foo you get the answer 1.

Other ways of causing word splitting include a judicious use of `eval':

    sentence="Longtemps, je me suis couch\+NOTRANS(é) de bonne heure."
    eval "words=($sentence)"

    args ${=sentence}

Note also the "$@" method of word splitting is always available in zsh functions and scripts (though strictly this does array splitting, not word splitting). This is more portable than the $*, since it will work regardless of the SH_WORD_SPLIT setting; the other difference is that $* removes empty arguments from the array. You can fix the first half of that objection by using ${==*}, which turns off SH_WORD_SPLIT for the duration of the expansion.

SH_WORD_SPLIT is set when zsh is invoked with the names `ksh' or `sh', or (entirely equivalent) when emulate ksh or emulate sh is in effect.

There is one other effect of word splitting which differs between ksh and zsh. In ksh, the builtin commands that declare parameters such as typeset and export force word-splitting not to take place after on an assignment argument:

    typeset param=`echo foo bar`

In which startup file do I put...?

When zsh starts up, there are four files you can change which it will run under various circumstances: .zshenv, .zprofile, .zshrc and .zlogin. They are usually in your home directory, but the variable $ZDOTDIR may be set to alter that. Here are a few simple hints about how to use them. There are also files which the system administrator can set for all shells; you can avoid running all except /etc/zshenv by starting zsh with the -f option --- for this reason it is important for administrators to make sure /etc/zshenv is as brief as possible.

The order in which the four files are searched (none of them need to exist) is the one just given. However, .zprofile and .zlogin are only run when the shell is a login shell --- when you first login, of course, and whenever you start zsh with the -l option. The order is the only difference between those; you should decide whether you need things set before or after .zshrc. These files are a good place to set environment variables (i.e. export commands), since they are passed on to all shells without you having to set them again, and also to check that your terminal is set up properly (except that if you want to change settings for terminal emulator windows like xterm you will need to put those in .zshrc, since usually you do not get a login shell here).

Login shells are often interactive, but this is not necessarily the case. It is the programme that starts the shell that decides if it is to be a login shell, and it is not required that the shell be run interactively. A possible example is a display manager that starts a shell to initialise your environment before running the window manager to create terminals: it might run this as a login shell but with no terminal, so it is not interactive.

The only file you can alter which is started with every zsh (unless you use the -f option) is .zshenv, so this is a good place to put things you want even if the shell is non-interactive: options for changing the syntax, like EXTENDED_GLOB, any changes to set with limit, any more variables you want to make sure are set as for example $fpath to find functions. You almost certainly do not want .zshenv to produce any output. Some people prefer not to use .zshenv for setting options, as this affects scripts; but making zsh scripts portable usually requires special handling anyway.

Finally, .zshrc is run for every interactive shell; that includes login shells, but also any other time you start up a shell, such as simply by typing zsh or opening a new terminal emulator window. This file is the place to change the editing behaviour via options or bindkey, control how your history is saved, set aliases unless you want to use them in scripts too, and for any other clutter which can't be exported but you only use when interacting directly with the shell. You probably don't want .zshrc to produce output, either, since there are occasions when this can be a problem, such as when using rsh from another host. See 3.21 for what to put in .zshrc to save your history.

What is the difference between `export' and the ALL_EXPORT option?

Normally, you would put a variable into the environment by using export var. The command setopt allexport causes all variables which are subsequently set (N.B. not all the ones which already exist) to be put into the environment.

This may seem a useful shorthand, but in practice it can have unhelpful side effects:

1. Since every variable is in the environment as well as remembered by the shell, the memory for it needs to be allocated twice. This is bigger as well as slower.
2. It really is every variable which is exported, even loop variables in for loops. This is probably a waste.
3. An arbitrary variable created by the user might have a special meaning to a command. Since all shell variables are visible to commands, there is no protection against this.

How do I turn off spelling correction/globbing for a single command?

In the first case, you presumably have setopt correctall in an initialisation file, so that zsh checks the spelling of each word in the command line. You probably do not want this behaviour for commands which do not operate on existing files.

The answer is to alias the offending command to itself with nocorrect stuck on the front, e.g.

    alias mkdir='nocorrect mkdir'

To turn off globbing, the rationale is identical:

    alias mkdir='noglob mkdir'

Note also that a shell function won't work: the no... directives must be expanded before the rest of the command line is parsed.

How do I get the Meta key to work on my xterm?

The Meta key isn't present on a lot of keyboards, but on some the Alt key has the same effect. If a character is typed on the keyboard while the Meta key is held down, the characters is sent as terminal input with its eighth bit set. For example, ASCII A, hex 65, becomes hex E5. This is sometimes used to provide extra editing commands.

As stated in the manual, zsh needs to be told about the Meta key by using bindkey -me or bindkey -mv in your .zshrc or on the command line. You probably also need to tell the terminal driver to allow the `Meta' bit of the character through; stty pass8 is the usual incantation. Sample .zshrc entry:

    [[ $TERM = "xterm" ]] && stty pass8 && bindkey -me

    [[ $TERM = "xterm" ]] && stty -parenb -istrip cs8 && bindkey -me

You don't need the bindkey to be able to define your own sequences with the Meta key, though you still need the stty.

If you are using multibyte input directly from the keyboard you probably don't want to use this feature since the eighth bit in each byte is used to indicate a part of a multibyte character. See chapter 5.

How do I automatically display the directory in my xterm title bar?

You should use the special function chpwd, which is called when the directory changes. The following checks that standard output is a terminal, then puts the directory in the title bar if the terminal is an xterm or some close relative, or a sun-cmd.

  chpwd() {
    [[ -t 1 ]] || return
    case $TERM in
      sun-cmd) print -Pn "\e]l%~\e\\"
        ;;
      *xterm*|rxvt|(dt|k|E)term) print -Pn "\e]2;%~\a"
        ;;
    esac
  }

Change %~ if you want the message to be different. (The -P option interprets such sequences just like in prompts, in this case producing the current directory; you can of course use $PWD here, but that won't use the ~ notation which I find clearer.) Note that when the xterm starts up you will probably want to call chpwd directly: just put chpwd in .zshrc after it is defined or autoloaded.

How do I make the completion list use eight bit characters?

If you are sure your terminal handles this, the easiest way from versions 3.0.6 and 3.1 of the shell is to set the option PRINT_EIGHT_BIT. In principle, this will work automatically if your computer uses the `locale' system and your locale variables are set properly, as zsh understands this. However, it is quite complicated, so if it isn't already set up, trying the option is a lot easier. For earlier versions of zsh 3, you are stuck with trying to understand locales, see the setlocale(3) and zshparam(1) manual pages: the simplest possibility may be to set LC_ALL=en_US. For older versions of the shell, there is no easy way out.

Why do the cursor (arrow) keys not work? (And other terminal oddities.)

The cursor keys send different codes depending on the terminal; zsh only binds the most well known versions. If you see these problems, try putting the following in your .zshrc:

    bindkey "$(echotc kl)" backward-char
    bindkey "$(echotc kr)" forward-char
    bindkey "$(echotc ku)" up-line-or-history
    bindkey "$(echotc kd)" down-line-or-history

If you use vi mode, use vi-backward-char and vi-forward-char where appropriate. As of version 4.0.1, zsh attempts to look up these codes and to set the key bindings for you (both emacs and vi), but in some circumstances this may not work.

Note, however, that up to version 3.0 binding arbitrary multiple key sequences can cause problems, so check that this works with your set up first. Also, from version 3.1.3, more sequences are supported by default, namely those in the form <ESC>O followed by A, B, C or D, as well as the corresponding set beginning <ESC>[, so this may be redundant.

A particular problem which sometimes occurs is that there are two different modes for arrow keys, normal mode and keypad mode, which send different sequences. Although this is largely a historical artifact, it sometimes happens that your terminal can be switched from one mode to the other, for example by a rogue programme that sends the sequence to switch one way, but not the sequence to switch back. Thus you are stuck with the effects. Luckily in this case the arrow key sequences are likely to be standard, and you can simply bind both sets. The following code does this.

    bindkey '\e[A'  up-line-or-history
    bindkey '\e[B'  down-line-or-history
    bindkey '\e[C'  forward-char
    bindkey '\e[D'  backward-char
    bindkey '\eOA'  up-line-or-history
    bindkey '\eOB'  down-line-or-history
    bindkey '\eOC'  forward-char
    bindkey '\eOD'  backward-char

It should be noted that the O / [ confusion can occur with other keys such as Home and End. Some systems let you query the key sequences sent by these keys from the system's terminal database, terminfo. Unfortunately, the key sequences given there typically apply to the mode that is not the one zsh uses by default (it's the "application" mode rather than the "raw" mode). Explaining the use of terminfo is outside the scope of this FAQ, but if you wish to use the key sequences given there you can tell the line editor to turn on "application" mode when it starts and turn it off when it stops:

    function zle-line-init () { echoti smkx }
    function zle-line-finish () { echoti rmkx }
    zle -N zle-line-init
    zle -N zle-line-finish

Why does my terminal act funny in some way?

If you are using an OpenWindows cmdtool as your terminal, any escape sequences (such as those produced by cursor keys) will be swallowed up and never reach zsh. Either use shelltool or avoid commands with escape sequences. You can also disable scrolling from the cmdtool pane menu (which effectively turns it into a shelltool). If you still want scrolling, try using an xterm with the scrollbar activated.

If that's not the problem, and you are using stty to change some tty settings, make sure you haven't asked zsh to freeze the tty settings: type

    ttyctl -u

On the other hand, if you aren't using stty and have problems you may need the opposite: ttyctl -f freezes the terminal to protect it from hiccups introduced by other programmes (kermit has been known to do this).

A problem I have experienced myself (on an AIX 3.2 workstation with xterm) is that termcap deinitialization sequences sent by `less' were causing automargins to be turned off --- not actually a shell problem, but you might have thought it was. The fix is to put `X' into the environment variable LESS to stop the sequences being sent. Other programs (though not zsh) may also send that sequence.

If that's not the problem, and you are having difficulties with external commands (not part of zsh), and you think some terminal setting is wrong (e.g. ^V is getting interpreted as `literal next character' when you don't want it to be), try

    ttyctl -u
    STTY='lnext "^-"' commandname

Why does zsh not work in an Emacs shell mode any more?

(This information comes from Bart Schaefer and other zsh-workers.)

Emacs 19.29 or thereabouts stopped using a terminal type of "emacs" in shell buffers, and instead sets it to "dumb". Zsh only kicks in its special I'm-inside-emacs initialization when the terminal type is "emacs".

Probably the most reliable way of dealing with this is to look for the environment variable $EMACS, which is set to t in Emacs' shell mode. Putting

    [[ $EMACS = t ]] && unsetopt zle

Another method is to put

    #!/bin/sh
    TERM=emacs exec zsh

    (setenv "ESHELL" (expand-file-name "~/bin/eshell"))

Why do my autoloaded functions not autoload [the first time]?

The problem is that there are two possible ways of autoloading a function (see the AUTOLOADING FUNCTIONS section of the zsh manual page zshmisc for more detailed information):

1. The file contains just the body of the function, i.e. there should be no line at the beginning saying function foo { or foo () {, and consequently no matching } at the end. This is the traditional zsh method. The advantage is that the file is called exactly like a script, so can double as both. To define a function xhead () { print -n "\033]2;$*\a"; }, the file would just contain print -n "\033]2;$*\a".
2. The file contains the entire definition, and maybe even other code: it is run when the function needs to be loaded, then the function itself is called up. This is the method in ksh. To define the same function xhead, the whole of the usual definition should be in the file.

In old versions of zsh, before 3.0, only the first behaviour was allowed, so you had to make sure the file found for autoload just contained the function body. You could still define other functions in the file with the standard form for definitions, though they would be redefined each time you called the main function.

In version 3.0.x, the second behaviour is activated if the file defines the autoloaded function. Unfortunately, this is incompatible with the old zsh behaviour which allowed you to redefine the function when you called it.

From version 3.1, there is an option KSH_AUTOLOAD to allow full ksh compatibility, i.e. the function must be in the second form above. If that is not set, zsh tries to guess which form you are using: if the file contains only a complete definition of the function in the second form, and nothing else apart from comments and whitespace, it will use the function defined in the file; otherwise, it will assume the old behaviour. The option is set if emulate ksh is in effect, of course.

(A neat trick to autoload all functions in a given directory is to include a line like autoload ~/fns/*(:t) in .zshrc; the bit in parentheses removes the directory part of the filenames, leaving just the function names.)

How does base arithmetic work?

The ksh syntax is now understood, i.e.

    let 'foo = 16#ff'

    (( foo = 16#ff ))

    foo=$((16#ff))

    (( foo = [16]ff ))

    echo $foo

    typeset -i foo

    typeset -i 10 foo

    print $(( [#16] 255 ))

How do I get a newline in my prompt?

You can place a literal newline in quotes, i.e.

    PROMPT="Hi Joe,
    what now?%# "

In recent versions of zsh (not 3.0), there is a form of quoting which interprets print sequences like `\n' but otherwise acts like single quotes: surround the string with $'...'. Hence:

    PROMPT=$'Hi Joe,\nwhat now?%# '

Why does bindkey ^a command-name or stty intr ^- do something funny?

You probably have the extendedglob option set in which case ^ and # are metacharacters. ^a matches any file except one called a, so the line is interpreted as bindkey followed by a list of files. Quote the ^ with a backslash or put quotation marks around ^a. See 3.27 if you want to know more about the pattern character ^.

Why can't I bind \C-s and \C-q any more?

The control-s and control-q keys now do flow control by default, unless you have turned this off with stty -ixon or redefined the keys which control it with stty start or stty stop. (This is done by the system, not zsh; the shell simply respects these settings.) In other words, \C-s stops all output to the terminal, while \C-q resumes it.

There is an option NO_FLOW_CONTROL to stop zsh from allowing flow control and hence restoring the use of the keys: put setopt noflowcontrol in your .zshrc file.

How do I execute command foo within function foo?

The command command foo does just that. You don't need this with aliases, but you do with functions. Note that error messages like

    zsh: job table full or recursion limit exceeded

Why do history substitutions with single bangs do something funny?

If you have a command like "echo !-2:$ !$", the first history substitution then sets a default to which later history substitutions with single unqualified bangs refer, so that !$ becomes equivalent to !-2:$. The option CSH_JUNKIE_HISTORY makes all single bangs refer to the last command.

Why does zsh kill off all my background jobs when I logout?

Simple answer: you haven't asked it not to. Zsh (unlike [t]csh) gives you the option of having background jobs killed or not: the nohup option exists if you don't want them killed. Note that you can always run programs with nohup in front of the pipeline whether or not the option is set, which will prevent that job from being killed on logout. (nohup is actually an external command.)

The disown builtin is very useful in this respect: if zsh informs you that you have background jobs when you try to logout, you can disown all the ones you don't want killed when you exit. This is also a good way of making jobs you don't need the shell to know about (such as commands which create new windows) invisible to the shell. Likewise, you can start a background job with &! instead of just & at the end, which will automatically disown the job.

How do I list all my history entries?

Tell zsh to start from entry 1: history 1. Those entries at the start which are no longer in memory will be silently omitted.

How does the alternative loop syntax, e.g. while {...} {...} work?

Zsh provides an alternative to the traditional sh-like forms with do,

    while TEST; do COMMANDS; done

To make it work you must make sure the TEST itself is clearly delimited. For example, this works:

    while (( i++ < 10 )) { echo i is $i; }

    while let "i++ < 10"; { echo i is $i; }   # Wrong!

So when using this syntax, the test following the while must be wrapped up: any of ((...)), [[...]], {...} or (...) will have this effect. (They have their usual syntactic meanings too, of course; they are not interchangeable.) Note that here too it is wrong to put in the semicolon, as then the case becomes identical to the preceding one:

    while (( i++ < 10 )); { echo i is $i; }   # Wrong!

The same is true of the if and until constructs:

    if { true } { echo yes } else { echo no }

    for foo in a b; { echo foo is $a; bar=$foo; }

This is independent of the behaviour of the SHORTLOOPS option (see manual), which you are in any case encouraged even more strongly not to use in programs as it can be very confusing.

Why is my history not being saved?

In zsh, you need to set three variables to make sure your history is written out when the shell exits. For example,

    HISTSIZE=200
    HISTFILE=~/.zsh_history
    SAVEHIST=200

How do I get a variable's value to be evaluated as another variable?

The problem is that you have a variable $E containing the string EDITOR, and a variable $EDITOR containing the string emacs, or something such. How do you get from $E to emacs in one easy stage?

There is no standard single-stage way of doing this. However, there is a zsh idiom (available in all versions of zsh since 3.0) for this:

    print ${(e)E:+\$$E}

For a standard shell way of doing this, you are stuck with eval:

    eval echo \$$E

Versions since 3.1.6 allow you to do this directly with a new flag; ${(P)E}.

As a slight aside, sometimes people note that the syntax ${${E}} is valid and expect it to have this effect. It probably ought to, but in the early days of zsh it was found convenient to have this way of producing different substitutions on the same parameter; for example, ${${file##**/}%.*} removes everything up to the last slash in $file, then everything from the last dot on, inclusive (try it, this works). So in ${${E}}, the internal ${...} actually does nothing.

How do I prevent the prompt overwriting output when there is no newline?

The problem is normally limited to zsh versions prior to 4.3.0 due to the advent of the PROMPT_SP option (which is enabled by default, and eliminates this problem for most terminals). An example of the overwriting is:

    % echo -n foo
    %

A better solution than disabling PROMPT_CR (for most terminals) is adding a simpler version of the PROMPT_SP functionality to an older zsh using a custom precmd function, like this one:

    # Skip defining precmd if the PROMPT_SP option is available.
    if ! eval '[[ -o promptsp ]] 2>/dev/null'; then
      function precmd {
        # Output an inverse char and a bunch spaces.  We include
        # a CR at the end so that any user-input that gets echoed
        # between this output and the prompt doesn't cause a wrap.
        print -nP "%B%S%#%s%b${(l:$((COLUMNS-1)):::):-}\r"
      }
    fi

One final alternative is to put a newline in your prompt -- see question 3.13 for that.

What's wrong with cut and paste on my xterm?

On the majority of modern UNIX systems, cutting text from one window and pasting it into another should work fine. On a few, however, there are problems due to issues about how the terminal is handled: most programs expect the terminal to be in `canonical input mode', which means that the program is passed a whole line of input at a time, while for editing the shell needs a single character at a time and must be in `non-canonical input mode'. On the systems in question, input can be lost or re-ordered when the mode changes. There are actually two slightly different problems:

1. When you paste something in while a programme is running, so that the shell only retrieves it later. Traditionally, there was a test which was used only on systems where the problem was known to exist, so it is possible some other systems were not handled (for example, certain versions of IRIX, it appears); also, continuation lines were not handled properly. A more reliable approach appears from versions 3.0.6 and 3.1.6.
2. When the shell is waiting for input, and you paste in a chunk of text consisting of more than one complete set of commands. Unfortunately, this is a much harder problem: the line editor is already active, and needs to be turned off when the first command is executed. The shell doesn't even know if the remaining text is input to a command or for the shell, so there's simply nothing it can do.

However, if you have problems you can trick it: type `{' on a line by itself, then paste the input, then type `}' on a line by itself. The shell will not execute anything until the final brace is read; all input is read as continuation lines (this may require the fixes referred to above in order to be reliable).

As of 5.1, this trick is not necessary on terminal emulators that support the bracketed paste feature (this includes most modern terminal emulators). See the description of $zle_bracketed_paste in the zshparam manual page for details.

How do I get coloured prompts on my colour xterm?

(Or `color xterm', if you're reading this in black and white.)

Versions of the shell starting with the 4.3 series have this built in. Use

    PS1='%K{white}%F{red}<red on white>%f%k<default colours>'

In older versions of the shell you need to find the sequences which generate the various colours from the manual for your terminal emulator; these are ANSI standard on those I know about which support colour. With a recent (post 3.1.6) distribution of zsh, there is a theme system to handle this for you; even if you don't see that, the installed function `colors' (meaning `colours', if you're not reading this in black and white) gives the escape sequences. You will end up with code looking like this (borrowed from Oliver Kiddle):

    PS1=$'%{\e[1;31m%}<the rest of your prompt here>%{\e[0m%}'

    PS1="$(print '%{\e[1;31m%}<the rest goes here>%{\e[0m%}')"

Why is my output duplicated with `foo 2>&1 >foo.out | bar'?

This is a slightly unexpected effect of the option MULTIOS, which is set by default. Let's look more closely:

    foo 2>&1 >foo.out | bar

    % { print output; print error >&2 } 2>&1 >foo.out | sed 's/error/erratic/'
    erratic
    output
    % cat foo.out
    output

It becomes clearer what's going on if we write:

    % print output >foo1.out >foo2.out
    % cat foo1.out
    output
    % cat foo2.out
    output

    % { print output; print error >&2 } 2>&1 >&- >foo.out | sed 's/error/erratic/'
    erratic

What are these `^' and `~' pattern characters, anyway?

The characters ^ and ~ are active when the option EXTENDED_GLOB is set. Both are used to exclude patterns, i.e. to say `match something other than ...'. There are some confusing differences, however. Here are the descriptions for ^ and ~.

^ means `anything except the pattern that follows'. You can think of the combination ^pat as being like a * except that it doesn't match pat. So, for example, myfile^.txt matches anything that begins with myfile except myfile.txt. Because it works with patterns, not just strings, myfile^*.c matches anything that begins with myfile unless it ends with .c, whatever comes in the middle --- so it matches myfile1.h but not myfile1.c.

Also like *, ^ doesn't match across directories if you're matching files when `globbing', i.e. when you use an unquoted pattern in an ordinary command line to generate file names. So ^dir1/^file1 matches any subdirectory of the current directory except one called dir1, and within any directory it matches it picks any file except one called file1. So the overall pattern matches dir2/file2 but not dir1/file1 nor dir1/file2 nor dir2/file1. (The rule that all the different bits of the pattern must match is exactly the same as for any other pattern character, it's just a little confusing that what does match in each bit is found by telling the shell not to match something or other.)

As with any other pattern, a ^ expression doesn't treat the character `/' specially if it's not matching files, for example when pattern matching in a command like [[ $string = ^pat1/pat2 ]]. Here the whole string pat1/pat2 is treated as the argument that follows the ^. So anything matches but that one string pat1/pat1.

It's not obvious what something like [[ $string = ^pat1^pat2 ]] means. You won't often have cause to use it, but the rule is that each ^ takes everything that follows as an argument (unless it's already inside parentheses --- I'll explain this below). To see this more clearly, put those arguments in parentheses: the pattern is equivalent to ^(pat1^(pat2)). where now you can see exactly what each ^ takes as its argument. I'll leave it as an exercise for you to work out what this does and doesn't match.

~ is always used between two patterns --- never right at the beginning or right at the end. Note that the other special meaning of ~, at the start of a filename to refer to your home directory or to another named directory, doesn't require the option EXTENDED_GLOB to be set. (At the end of an argument ~ is never special at all. This is useful if you have Emacs backup files.) It means `match what's in front of the tilde, but only if it doesn't match what's after the tilde'. So *.c~f* matches any file ending in .c except one that begins with f. You'll see that, unlike ^, the parts before and after the ~ both refer separately to the entire test string.

For matching files by globbing, ~ is the only globbing operator to have a lower precedence than /. In other words, when you have /a/path/to/match~/a/path/not/to/match the ~ considers what's before as a complete path to a file name, and what's after as a pattern to match against that file. You can put any other pattern characters in the expressions before and after the ~, but as I said the pattern after the ~ is really just a single pattern to match against the name of every file found rather than a pattern to generate a file. That means, for example, that a * after the ~ will match a /. If that's confusing, you can think of how ~ works like this: take the pattern on the left, use it as normal to make a list of files, then for each file found see if it matches the pattern on the right and if it does take that file out of the list. Note, however, that this removal of files happens immediately, before anything else happens to the file list --- before any glob qualifiers are applied, for example.

One rule that is common to both ^ and ~ is that they can be put inside parentheses and the arguments to them don't extend past the parentheses. So (^README).txt matches any file ending in .txt unless the string before that was README, the same as *.txt~README.txt or (*~README).txt. In fact, you can always turn ^something into (*~something), where something mustn't contain / if the pattern is being used for globbing.

Likewise, abc+LPAR()<->~<10-100>RPAR().txt matches a file consisting of abc, then some digits, then .txt, unless the digits happen to match a number from 10 to 100 inclusive (remember the handy <-> pattern for matching integers with optional limits to the range). So this pattern matches abc1.txt or abc200.txt but not abc20.txt nor abc100.txt nor even abc0030.txt. However, if you're matching files by globbing note you can't put /s inside the parentheses since the groups can't stretch across multiple directories. (You can do that, of course, whenever the character / isn't special.) This means that you need to take care when using exclusions across multiple directories; see some examples below.

You may like to know that from zsh 5.0.3 you can disable any pattern character separately. So if you find ^ gets in your way and you're happy using ~, put disable -p "^" in ~/.zshrc. You still need to turn on EXTENDED_GLOB; the disable command only deactivates things that would otherwise be active, you can't specially enable something not allowed by the syntax options in effect.

Here are some examples with files to illustrate the points. We'll assume the option EXTENDED_GLOB is set and none of the pattern characters is disabled.

1. **/foo~*bar* matches any file called foo in any subdirectory, except where bar occurred somewhere in the path. For example, users/barstaff/foo will be excluded by the ~ operator. As the ** operator cannot be grouped (inside parentheses it is treated as *), this is one way to exclude some subdirectories from matching a **. Note that this can be quite inefficient because the shell performs a complete search for **/foo before it uses the pattern after the ~ to exclude files from the match. The file is excluded if bar occurs anywhere, in any directory segment or the final file name.
2. The form (^foo/)# can be used to match any hierarchy of directories where none of the path components is foo. For example, (^CVS/)# selects all subdirectories to any depth except where one component is named CVS. (The form (pat/)# is very useful in other cases; for example, (../)#.cvsignore finds the file .cvsignore if it exists in the current directory or any parent.)

How do I edit the input buffer in $EDITOR?

When typing a long command interactively, it's possible to edit it in $EDITOR before execution by using the edit-command-line ZLE widget. For example, after putting

    autoload -U edit-command-line;
    zle -N edit-command-line;
    bindkey '^Fc' edit-command-line;

Why does `which' output for missing commands go to stdout?

The issue is that if you run:

    which non-existent-command

The original reason for this is that this behaviour is inherited from previous versions of `which', a builtin in later versions of csh, the C shell, as well as tcsh, an adaptation of the C Shell with better editing, and is also available as a separate script sometimes still found in certain distributions. Other shells had equivalent commands, `whence' and `type, that zsh has also adopted. So in fact this has always been a feature of `which'. (It would be possible to change this in emulation modes; however, so far this possibility has been seen as more of an additional confusion than a help.)

If you want some further rationalisation, you might note that `which' is designed as a way of outputting information about a command. So `this command can be found in ...' and `this command can't be found' are both bits of information here, unlike the case where the command is to be executed. So although it differs from other Bourne-style shells it is in fact self-consistent. Note that the exit status does reflect the fact the command can't be found.

Why doesn't the expansion *.{tex,aux,pdf} do what I expect?

Based on the behaviour of some other shells, you might guess that the following expression:

    echo *.{tex,aux,pdf}

The reason for this is that the brace expansion isn't actually a form of pattern matching. Instead, the line above is equivalent to

    echo *.tex *.aux *.pdf

However, there is a way of doing exactly what you want, using parentheses instead of braces:

    echo *.(tex|aux|pdf)

This use of parentheses is special to zsh. Modern Bourne-like shells have a syntax like this, too, but with an @ in front of the parentheses: again, see 2.1, and search for @+LPAR(). This is harder for the user to remember but easier for the shell to parse!

The mysteries of completion

What is completion?

`Completion' is where you hit a particular command key (TAB is the standard one) and the shell tries to guess the word you are typing and finish it for you --- a godsend for long file names, in particular, but in zsh there are many, many more possibilities than that.

There is also a related process, `expansion', where the shell sees you have typed something which would be turned by the shell into something else, such as a variable turning into its value ($PWD becomes /home/users/mydir) or a history reference (!! becomes everything on the last command line). In zsh, when you hit TAB it will look to see if there is an expansion to be done; if there is, it does that, otherwise it tries to perform completion. (You can see if the word would be expanded --- not completed --- by TAB by typing \C-x g, which lists expansions.) Expansion is generally fairly intuitive and not under user control; for the rest of the chapter I will discuss completion only.

An elegant completion system appeared in version 4, replacing the old compctl command. This is based on functions called automatically for completion in particular contexts (for example, there is a function called _cd to handle completion for the cd command) and is installed automatically with the shell, so all you need to do, in principal, is to arrange for this to be loaded. Putting `autoload -U compinit; compinit' in your .zshrc should be enough if the system is installed properly.

What sorts of things can be completed?

The simplest sort is filename completion, mentioned above. Unless you have made special arrangements, as described below, then after you type a command name, anything else you type is assumed by the completion system to be a filename. If you type part of a word and hit TAB, zsh will see if it matches the first part a filename and if it does it will automatically insert the rest.

The other simple type is command completion, which applies (naturally) to the first word on the line. In this case, zsh assumes the word is some command to be executed lying in your $PATH (or something else you can execute, like a builtin command, a function or an alias) and tries to complete that.

However, the new completion system is highly sensitive to context and comes with completions for many UNIX commands. These are automatically loaded when you run compinit as described above. So the real answer to the question `what can be completed?' is `anything where an automated guess is possible'. Just hit TAB and see if the shell manages to guess correctly.

How does zsh deal with ambiguous completions?

Often there will be more than one possible completion: two files start with the same characters, for example. Zsh has a lot of flexibility for what it does here via its options. The default is for it to beep and completion to stop until you type another character. You can type \C-D to see all the possible completions. (That's assuming you're at the end of the line, otherwise \C-D will delete the next character and you have to use ESC-\C-D.) This can be changed by the following options, among others:

• with NO_BEEP set, that annoying beep goes away
• with NO_LIST_BEEP, beeping is only turned off for ambiguous completions
• with AUTO_LIST set, when the completion is ambiguous you get a list without having to type \C-D
• with BASH_AUTO_LIST set, the list only happens the second time you hit tab on an ambiguous completion
• with LIST_AMBIGUOUS, this is modified so that nothing is listed if there is an unambiguous prefix or suffix to be inserted --- this can be combined with BASH_AUTO_LIST, so that where both are applicable you need to hit tab three times for a listing.
• with MENU_COMPLETE set, one completion is always inserted completely, then when you hit TAB it changes to the next, and so on until you get back to where you started
• with AUTO_MENU, you only get the menu behaviour when you hit TAB again on the ambiguous completion.
• Finally, although it affects all completion lists, including those explicitly requested, note also ALWAYS_LAST_PROMPT, which causes the cursor to return to the line you were editing after printing the list, provided that is short enough.

How do I complete in the middle of words / just what's before the cursor?

Sometimes you have a word on the command-line which is incomplete in the middle. Normally if you hit tab in zsh, it will simply go to the end of the word and try to complete there. However, there are two ways of changing this.

First, there is the option COMPLETE_IN_WORD. This tries to fill in the word at the point of the cursor. For example, if the current directory contains foobar, then with the option set, you can complete fbar to foobar by moving the cursor to the b and hitting tab.

To complete just what's before the cursor, ignoring anything after, you need the function expand-or-complete-prefix: it works mostly like the usual function bound to tab, but it ignores anything on the right of the cursor. If you always want this behaviour (some other shells do this), bind it to tab; otherwise put another binding, e.g. ^X TAB in ~/.zshrc:

    bindkey "^X^I" expand-or-complete-prefix

The completion system's handling of filenames allows you to complete multiple segments of a path in one go, so for example /u/l/b can expand to /usr/local/bin or anything else that matches. This saves you having to expand the middle part of the path separately.

How do I get started with programmable completion?

The main resource is the zshcompsys manual page. It's complicated, I'm afraid, far too much to go into here. See also the user guide referred to above, or copy one of the very many existing functions. For a professionally produced guide, see the book `From Bash to Z Shell: Conquering the Command Line' by Oliver Kiddle, Jerry Peek and Peter Stephenson (me), published by Apress, ISBN 1-59059-376-6. Chapter 10 tells you how to configure the completion system and chapter 15 how to write your own completion functions.

Suppose I want to complete all files during a special completion?

If you're using the completion system the shell will decide what to complete when you hit TAB. That's usually the right thing for the context, but sometimes you just want to complete files, like TAB used to do in the old days. You can set up this up as follows:

    zle -C complete-file complete-word _generic
    zstyle ':completion:complete-file::::' completer _files
    bindkey '^xF' complete-file

Note the way the form of completion to use is specified by picking a `completer' called `_files'. You can define any completion to be bound to a keystroke by putting the appropriate completion function at that point. Then change all occurrences of `complete-file' to a name of your own.

If you simply want to try filename completion as a default when other completions fail, add it to the `completer' style for normal completion, for example:

    zstyle ':completion:*' completer _complete _ignored _files

Multibyte input and output

What is multibyte input?

For a long time computers had a simple idea of a character: each octet (8-bit byte) of text contained one character. This meant an application could only use 256 characters at once. The first 128 characters (0 to 127) on Unix and similar systems usually corresponded to the ASCII character set, as they still do. So all other possibilities had to be crammed into the remaining 128. This was done by picking the appropriate character set for the use you were making. For example, ISO 8859 specified a set of extensions to ASCII for various alphabets.

This was fine for simple extensions and certain short enough relatives of the Latin alphabet (with no more than a few dozen alphabetic characters), but useless for complex alphabets. Also, having a different character set for each language is inconvenient: you have to start a new terminal to run the shell with each character set. So the character set had to be extended. To cut a long story short, the world has mostly standardised on a character set called Unicode, related to the international standard ISO 10646. The intention is that this will contain every single character used in all the languages of the world.

This has far too many characters to fit into a single octet. What's more, UNIX utilities such as zsh are so used to dealing with ASCII that removing it would cause no end of trouble. So what happens is this: the 128 ASCII characters are kept exactly the same (and they're the same as the first 128 characters of Unicode), but the remaining 128 characters are used to build up any other Unicode character by combining multiple octets together. The shell doesn't need to interpret these directly; it just needs to ask the system library how many octets form the next character, and if there's a valid character there at all. (It can also ask the system what width the character takes up on the screen, so that characters no longer need to be exactly one position wide.)

The way this is done is called UTF-8. Multibyte encodings of other character sets exist (you might encounter them for Asian character sets); zsh will be able to use any such encoding as long as it contains ASCII as a single-octet subset and the system can provide information about other characters. However, in the case of Unicode, UTF-8 is the only one you are likely to encounter that is useful in zsh.

(In case you're confused: Unicode is the character set, while UTF-8 is an encoding of it. You might hear about other encodings, such as UCS-2 and UCS-4 which are basically the character's index in the character set as a two-octet or four-octet integer. You might see files encoded this way, for example on Windows, but the shell can't deal directly with text in those formats.)

How does zsh handle multibyte input and output?

Until version 4.3, zsh didn't handle multibyte input properly at all. Each octet in a multibyte character would look to the shell like a separate character. If your terminal handled the character set, characters might appear correct on screen, but trying to edit them would cause all sorts of odd effects. (It was possible to edit in zsh using single-byte extensions of ASCII such as the ISO 8859 family, however.)

From version 4.3.4 (stable versions starting from 5.0), multibyte input is handled in the line editor if zsh has been compiled with the appropriate definitions, and is automatically activated. This is indicated by the option MULTIBYTE, which is set by default on shells that support multibyte mode. Hence you can test this with a standard option test: `[[ -o multibyte ]]'.

The MULTIBYTE option affects the entire shell: parameter expansion, pattern matching, etc. count valid multibyte character strings as a single character. You can unset the option locally in a function to revert to single-byte operation.

As multibyte characters are nowadays standard across most utilities, since 5.1 the MULTBYTE option has been turned on when emulating other shells.

The other option that affects multibyte support is COMBINING_CHARS, new in version 4.3.9. When this is set, any zero-length punctuation characters that follow an alphanumeric character (the base character) are assumed to be modifications (accents etc.) to the base character and to be displayed within the same screen area as the base character. As not all terminals handle this, even if they correctly display the base multibyte character, this option is not on by default. Recent versions of the KDE and GNOME terminal emulators konsole and gnome-terminal as well as rxvt-unicode, and the Unicode version of xterm, xterm -u8 or the front-end uxterm, are known to handle combining characters.

The COMBINING_CHARS option only affects output; combining characters may always be input, but when the option is off will be displayed specially. By default this is as a code point (the index of the character in the character set) between angle brackets, usually in inverse video. Highlighting of such special characters can be modified using the new array parameter zle_highlight.

How do I ensure multibyte input and output work on my system?

Once you have a version of zsh with multibyte support, you need to ensure the environment is correct. We'll assume you're using UTF-8. Many modern systems may come set up correctly already. Try one of the editing widgets described in the next section to see.

There are basically three components.

• The locale. This describes a whole series of features specific to countries or regions of which the character set is one. Usually it is controlled by the environment variable LANG (there are others but this is the one to start with). If you have a recent operating system, very likely it is already set appropriately. Otherwise, you need to find a locale whose name contains UTF-8. This will be a variant on your usual locale, which typically indicates the language and country; for example, mine is en_GB.UTF-8. Luckily, zsh can complete locale names, so if you have the new completion system loaded you can type export LANG= and attempt to complete a suitable locale. It's the locale that tells the shell to expect the right form of multibyte input. (However, there's no guarantee that the shell is actually going to get this input: for example, if you edit file names that have been created using a different character set it won't work properly.)
• The terminal emulator. Those that are supplied with a recent desktop environment, such as konsole and gnome-terminal, are likely to have extensive support for localization and may work correctly as soon as they know the locale. You can enable UTF-8 support for xterm in its application defaults file. The following are the relevant resources; you don't actually need all of them, as described below. If you use a ~/.Xdefaults or ~/.Xresources file for setting resources, prefix all the lines with xterm:

  
          *wideChars: true
          *locale: true
          *utf8: 1
          *vt100Graphics: true
  
  

  This turns on support for wide characters (this is enabled by the utf8 resource, too); enables conversions to UTF-8 from other locales (this is the key resource and actually overrides utf8); turns on UTF-8 mode (this resource is mostly used to force use of UTF-8 characters if your locale system isn't up to it); and allows certain graphic characters to work even with UTF-8 enabled. (Thanks to Phil Pennock for suggestions.)
• The font. If you selected this from a menu in your terminal emulator, there's a good chance it already selected the right character set to go with it. If you hand-picked an old fashioned X font with a lot of dashes, you need to make sure it ends with the right character encoding, iso10646-1 (and not, for example, iso8859-1). Not all characters will be available in any font, and some fonts may have a more restricted range of Unicode characters than others.

As mentioned in the previous section, bindkey -m now outputs a warning message telling you that multibyte input from the terminal is likely not to work. (See 3.5 if you don't know what this feature does.) If your terminal doesn't have characters that need to be input as multibyte, however, you can still use the meta bindings and can ignore the warning message. Use bindkey -m 2>/dev/null to suppress it.

You might also note that the latest version of the Cygwin environment for Windows supports UTF-8. In previous versions, zsh was able to compile with the MULTIBYTE option enabled, but the system didn't provide full support for it.

How can I input characters that aren't on my keyboard?

Two functions are provided with zsh that help you input characters. As with all editing widgets implemented by functions, you need to mark the function for autoload, create the widget, and, if you are going to use it frequently, bind it to a key sequence. The following binds insert-composed-char to F5 on my keyboard:

    autoload -Uz insert-composed-char
    zle -N insert-composed-char
    bindkey '\e[15~' insert-composed-char

The two widgets are described in the zshcontrib(1) manual page, but here is a brief summary:

insert-composed-char is followed by two characters that are a mnemonic for a multibyte character. For example a: is a with an Umlaut; cH is the symbol for hearts on a playing card. Various accented characters, European and related alphabets, and punctuation and mathematical symbols are available. The mnemonics are mostly those given by RFC 1345.

insert-unicode-char is used to input a Unicode character by its hexadecimal number. This is the number given in the Unicode character charts, see for example https://www.unicode.org/charts/. You need to execute the function, then type the hexadecimal number (you can omit any leading zeroes), then execute the function again.

Both functions can be used without multibyte mode, provided the locale is correct and the character selected exists in the current character set; however, using UTF-8 massively extends the number of valid characters that can be produced.

If you have a recent X Window System installation, you might find the AltGr key helps you input accented Latin characters; for example on my keyboard AltGr-; e gives e with an acute accent. See also https://www.cl.cam.ac.uk/~mgk25/unicode.html#input for general information on entering Unicode characters from a keyboard.

The future of zsh

What bugs are currently known and unfixed? (Plus recent important changes)

Bugs tend to be tracked on the zsh-workers mailing list; see the next section. Check the mailing list to see if a bug has been reported. (There is a bug tracker at the zsh development site at Sourceforge, but it's not in active use.)

To see how recent versions of the shell have changed, look at the README file in the source distribution. This indicates the most important changes, and in particular draws attention to incompatibilities you might notice.

Where do I report bugs, get more info / who's working on zsh?

The shell is being maintained by various (entirely self-appointed) subscribers to the mailing list,

    zsh-workers@zsh.org

Note that this location has just changed (January 1999), and the instructions to go with it are slightly different --- in particular, if you are already subscribed, the instructions about how to unsubscribe are different.

Please note when reporting bugs that many exist only on certain architectures, which the developers may not have access to. In this case debugging information, as detailed as possible, is particularly welcome.

Two progressively lower volume lists exist, one with messages concerning the use of zsh,

    zsh-users@zsh.org

    zsh-announce@zsh.org

Note that you should only join one of these lists: people on zsh-workers receive all the lists, and people on zsh-users will also receive the announcements list.

The lists are handled by an automated server. The instructions for zsh-announce and zsh-users are the same as for zsh-workers: just change zsh-workers to whatever in the following.

To join zsh-workers, send email to

    zsh-workers-subscribe@zsh.org

An archive of mailings for the last few years can be found at https://www.zsh.org/mla/ at the main zsh archive in Australia.

Of course, you can also post zsh queries to the Usenet group comp.unix.shell; if all else fails, you could even e-mail me.

Acknowledgments:

Thanks to zsh-list, in particular Bart Schaefer, for suggestions regarding this document. Zsh has been in the hands of archivists Jim Mattson, Bas de Bakker, Richard Coleman, Zoltan Hidvegi and Andrew Main, and the mailing list has been run by Peter Gray, Rick Ohnemus, Richard Coleman, Karsten Thygesen and Geoff Wing, all of whom deserve thanks. The world is eternally in the debt of Paul Falstad for inventing zsh in the first place (though the wizzo extended completion is by Sven Wischnowsky).

Copyright Information:

This document is copyright (C) P.W. Stephenson, 1995, 1996, 1997, 1998, 1999, 2000, 2012. This text originates in the U.K. and the author asserts his moral rights under the Copyrights, Designs and Patents Act, 1988.

Permission is hereby granted, without written agreement and without license or royalty fees, to use, copy, modify, and distribute this documentation for any purpose, provided that the above copyright notice appears in all copies of this documentation. Remember, however, that this document changes monthly and it may be more useful to provide a pointer to it rather than the entire text. A suitable pointer is "information on the Z-shell can be obtained on the World Wide Web at URL https://zsh.fyi".

zsh.fyi just now