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Z-shell (zsh) Frequently-Asked Questions


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Archive-Name: unix-faq/shell/zsh
Last-Modified: 2002/08/25
Submitted-By: pws@pwstephenson.fsnet.co.uk (Peter Stephenson)
Posting-Frequency: Monthly
Copyright: (C) P.W. Stephenson, 1995--2001 (see end of document)

See reader questions & answers on this topic! - Help others by sharing your knowledge
Changes since last issue posted:

  1.5 4.0.6 released.

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.

Notation: Quotes `like this' are ordinary textual quotation
marks.  Other uses of quotation marks are input to the shell.

Contents:
Chapter 1:  Introducing zsh and how to install it
1.1. Sources of information
1.2. What is it?
1.3. What is it good at?
1.4. On what machines will it run?  (Plus important compilation notes)
1.5. What's the latest version?
1.6. Where do I get it?
1.7. I don't have root access: how do I make zsh my login shell?

Chapter 2:  How does zsh differ from...?
2.1. sh and ksh?
2.2. csh?
2.3. Why do my csh aliases not work?  (Plus other alias pitfalls.)
2.4. tcsh?
2.5. bash?
2.6. Shouldn't zsh be more/less like ksh/(t)csh?

Chapter 3:  How to get various things to work
3.1. Why does `$var' where `var="foo bar"' not do what I expect?
3.2. In which startup file do I put...?
3.3. What is the difference between `export' and the ALL_EXPORT option?
3.4. How do I turn off spelling correction/globbing for a single command?
3.5. How do I get the meta key to work on my xterm?
3.6. How do I automatically display the directory in my xterm title bar?
3.7. How do I make the completion list use eight bit characters?
3.8. Why do the cursor (arrow) keys not work?
3.9. Why does my terminal act funny in some way?
3.10. Why does zsh not work in an Emacs shell mode any more?
3.11. Why do my autoloaded functions not autoload [the first time]?
3.12. How does base arithmetic work?
3.13. How do I get a newline in my prompt?
3.14. Why does `bindkey ^a command-name' or 'stty intr ^-' do something funny?
3.15. Why can't I bind \C-s and \C-q any more?
3.16. How do I execute command `foo' within function `foo'?
3.17. Why do history substitutions with single bangs do something funny?
3.18. Why does zsh kill off all my background jobs when I logout?
3.19. How do I list all my history entries?
3.20. How does the alternative loop syntax, e.g. `while {...} {...}' work?
3.21. Why is my history not being saved?
3.22. How do I get a variable's value to be evaluated as another variable?
3.23. How do I prevent the prompt overwriting output when there is no newline?
3.24. What's wrong with cut and paste on my xterm?
3.25. How do I get coloured prompts on my colour xterm?
3.26. Why is my output duplicated with `foo 2>&1 >foo.out | bar'?
3.27. Why am I prompted to correct commands which are in my path?

Chapter 4:  The mysteries of completion
4.1. What is completion?
4.2. What sorts of things can be completed?
4.3. How does zsh deal with ambiguous completions?
4.4. How do I complete in the middle of words / just what's before the cursor?
4.5. How do I get started with programmable completion?
4.6. And if programmable completion isn't good enough?

Chapter 5:  The future of zsh
5.1. What bugs are currently known and unfixed? (Plus recent important changes)
5.2. Where do I report bugs, get more info / who's working on zsh?
5.3. What's on the wish-list?
5.4. Did zsh have problems in the year 2000?

Acknowledgments

Copyright
--- End of Contents ---

Chapter 1: Introducing zsh and how to install it

1.1: Sources of information

  Information on zsh is available via the World Wide Web.  The URL
  is http://zsh.sunsite.dk/ .
  The server provides this FAQ and much else and is
  now maintained by Karsten Thygesen and others (mail zsh@sunsite.dk
  with any related messages).  The FAQ is at http://zsh.sunsite.dk/FAQ/ .
  The site also contains some contributed zsh scripts and functions;
  we are delighted to add more, or simply links to your own collection.

  This document was originally written in YODL, allowing it to be converted
  easily into various other formats.  The master source file lives at
  http://zsh.sunsite.dk/FAQ/zshfaq.yo and the plain text version
  can be found at http://zsh.sunsite.dk/FAQ/zshfaq.txt .

  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; see

    USA         http://www.cis.ohio-state.edu/hypertext/faq/usenet/top.html
    UK          http://www.lib.ox.ac.uk/internet/news/faq/comp.unix.shell.html
    Netherlands http://www.cs.uu.nl/wais/html/na-dir/unix-faq/shell/.html

  You can also get it via email by emailing mail-server@rtfm.mit.edu
  with, in the body of the message, `send faqs/unix-faq/shell/zsh'.

  The latest version of this FAQ is also available directly from any
  of the zsh archive sites listed in question 1.6.

  I have been putting together a user guide to complement the manual by
  explaining the most useful features of zsh in a more easy to read way.
  This is now more than half complete and includes a discussion of
  the new form for command line completion, not described in the FAQ.
  You can find it in various formats at:
    http://zsh.sunsite.dk/Guide/

  (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.

1.2: 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.

1.3: 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).

  o  Command line editing:

    o  programmable completion: incorporates the ability to use the
       full power of zsh's globbing and shell programming features,
    o  multi-line commands editable as a single buffer (even files!),
    o  variable editing (vared),
    o  command buffer stack,
    o  print text straight into the buffer for immediate editing (print -z),
    o  execution of unbound commands,
    o  menu completion in two flavours,
    o  variable, editing function and option name completion,
    o  inline expansion of variables and history commands.  

  o  Globbing --- extremely powerful, including:

    o  recursive globbing (cf. find),
    o  file attribute qualifiers (size, type, etc. also cf. find),
    o  full alternation and negation of patterns.

  o  Handling of multiple redirections (simpler than tee).
  o  Large number of options for tailoring.
  o  Path expansion (=foo -> /usr/bin/foo).
  o  Adaptable messages for spelling, watch, time as well as prompt
     (including conditional expressions).
  o  Named directories.
  o  Comprehensive integer and floating point arithmetic.
  o  Manipulation of arrays (including reverse subscripting).
  o  Associative arrays (key-to-value hashes)
  o  Spelling correction.

1.4: 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 Etc/MACHINES in the distribution has more details.

  There are also now separate ports for Windows and OS/2, see `Where
  do I get it' 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 Etc/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.

1.5: What's the latest version?

  Zsh 4.0.6 is the latest production version.  The major number 4.0
  reflects major improvements to modularity and to improvements in
  the editor, programmable completion and many other smaller features
  over the 3.0 series.  (The previous widely available release was
  4.0.4.)

  There will not be any further 3.0 releases now that 4.0 has become
  the stable version.  However, a few patches to 3.0.8 are available from
  the patch manager at Sourceforge, http://sourceforge.net/patch/?group_id=4068
  Official patches are posted by Bart Schaefer (user name barts).

  A beta of the next version is often 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.

1.6: 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.  The following are known mirrors (kept frequently up to date); the
  first is the official archive site, currently in Australia.  All are
  available by anonymous FTP.  The major sites keep test versions 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.  The following list also appears on the WWW at
  http://www.zsh.org .

    Home site ftp://ftp.zsh.org
              http://www.zsh.org/pub/zsh/
    Denmark   ftp://sunsite.dk/pub/unix/shells/zsh
    Finland   ftp://ftp.funet.fi/pub/unix/shells/zsh/
    Germany   ftp://ftp.fu-berlin.de/pub/unix/shells/zsh/
    Hungary   ftp://ftp.cs.elte.hu/pub/zsh/
              (also http://www.cs.elte.hu/pub/zsh/ )
              ftp://ftp.kfki.hu/pub/packages/zsh/
    Israel    ftp://ftp.math.technion.ac.il/pub/zsh/
              (also http://www.math.technion.ac.il/pub/zsh/ )
    Japan     ftp://ftp.win.ne.jp/pub/shell/zsh/
              ftp://ftp.ayamura.org/pub/zsh/
    Korea     ftp://linux.sarang.net/mirror/system/shell/zsh/
    Netherlands ftp://ftp.demon.nl/pub/mirrors/zsh/
    Norway    ftp://ftp.uit.no/pub/unix/shells/zsh/
    Poland    ftp://sunsite.icm.edu.pl/pub/unix/shells/zsh/
    Romania   ftp://ftp.roedu.net/pub/mirrors/ftp.zsh.org/pub/zsh/
              ftp://ftp.kappa.ro/pub/mirrors/ftp.zsh.org/pub/zsh/
    Slovenia  ftp://ftp.siol.net/mirrors/zsh/
    Sweden    ftp://ftp.lysator.liu.se/pub/unix/zsh/
    UK        ftp://ftp.net.lut.ac.uk/zsh/
              (also by FSP at port 21)
              ftp://sunsite.org.uk/packages/zsh/
    USA       ftp://uiarchive.uiuc.edu/mirrors/ftp/ftp.zsh.org/pub/
              ftp://ftp.rge.com/pub/shells/zsh/
              http://zsh.disillusion.org/
              http://foad.org/zsh/

  The Windows port mentioned above is maintained separately by Amol
  Deshpande <amold@microsoft.com>; please mail Amol directly about any
  Windows-specific problems.  This is based on 3.0.5, and probably will
  not be developed further.  You can get it from:

            ftp://ftp.blarg.net/users/amol/  

  There is no port of 4.0 for Windows, but newer releases compile under
  Cygwin, a freely available UNIX-style environment for the Win32 API.  You
  can find information about this at 
  http://sourceware.cygnus.com/cygwin.

  Likewise the OS/2 port is available from TAMURA Kent
  <kent@tril.ibm.co.jp> at

            http://www.haun.org/kent/tmp/

  Starting from mid-October 1997, there is an archive of patches sent
  to the maintainers' mailing list.  Note that these may not all be
  added to the shell, and some may already have been; you simply have
  to search for something you might want which is not in the version
  you have.  Also, there may be some prerequisites earlier in the
  archive.  It can be found on the zsh WWW pages (as described in
  1.1) at:

            http://zsh.sunsite.dk/Patches/

1.7: 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:

    [ x$ZSH_VERSION = x -a -f $HOME/bin/zsh ] && exec $HOME/bin/zsh -l

  --- the first test is a safeguard to avoid an infinite loop in case
  your zsh is set up to source your .profile, which is quite a common
  trick as you can save a lot of duplication that way.  If your login
  shell is csh or tcsh, put this in .login:

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

  (in each case the `-l' tells zsh it is a login shell).

  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
    }

  and for C-shell-like shells:

    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. 

  There was a thread on this topic on the zsh-workers mailing list,
  starting from item 15747.  You can find this at http://www.zsh.org/mla/.

  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.

Chapter 2: 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.

2.1: Differences from sh and ksh

  (The following refers to shell options extensively.  To turn an
  option on in zsh you use `setopt var(optionname)', and to turn
  it off you use `unsetopt var(optionname)'.  The option name is
  case insensitive and underscores are ignored.  If you are used to ksh,
  that syntax works too.)

  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 4.0 (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_BUILTINS, 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. 

  o  Syntax:

    o * Shell word splitting: see question 3.1.
    o * 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.
    o   Coprocesses are established by `coproc'; `|&' behaves like
        csh.  Handling of coprocess file descriptors is also different.
    o   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.

  o  Command line substitutions, globbing etc.:

    o * Failure to match a globbing pattern causes an error (use
        NO_NOMATCH).
    o * The results of parameter substitutions are treated as plain text:
        `foo="*"; print $foo' prints all files in ksh but `*' in zsh
        (uset GLOB_SUBST).
    o * $PSn do not do parameter substitution by default (use PROMPT_SUBST).
    o * 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] Note that `~' is the only globbing operator to have a lower
        precedence than `/'.  For example, `**/foo~*bar*' matches any
        file in a subdirectory called `foo', except where `bar'
        occurred somewhere in the path (e.g. `users/barstaff/foo' will
        be excluded by the `~' operator).  As the `**' operator cannot
        be grouped (inside parentheses it is treated as `*'), this is
        the way to exclude some subdirectories from matching a `**'.
    o   Unquoted assignments do file expansion after `:'s (intended for
        PATHs). 
    o   `integer' does not allow `-i'.
    o   `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.

  o  Command execution:

    o * There is no $ENV variable (use /etc/zshrc, ~/.zshrc; 
        note also $ZDOTDIR).
    o   $PATH is not searched for commands specified
        at invocation without -c.

  o  Aliases and functions:

    o   The order in which aliases and functions are defined is significant:
        function definitions with () expand aliases -- see question 2.3.
    o   Aliases and functions cannot be exported.
    o   There are no tracked aliases: command hashing replaces these.
    o   The use of aliases for key bindings is replaced by `bindkey'.
    o * 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).
    o   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.

    o  Traps and signals:

    o * Traps are not local to functions.  The option LOCAL_TRAPS is
          available from 3.1.6.
    o   TRAPERR has become TRAPZERR (this was forced by UNICOS which
        has SIGERR).

  o  Editing:

    o   The options emacs, gmacs, viraw are not supported.
        Use bindkey to change the editing behaviour: `set -o {emacs,vi}'
        becomes `bindkey -{e,v}'; for gmacs, go to emacs mode and use
        `bindkey \^t gosmacs-transpose-characters'.
    o   The `keyword' option does not exist and `-k' is instead
        interactivecomments.  (`keyword' will not be in the next ksh
        release either.)
    o * 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.
    o   `\' does not escape editing chars (use `^V').
    o   Not all ksh bindings are set (e.g. `<ESC>#'; try `<ESC>q').
    o * `#' in an interactive shell is not treated as a comment by
        default. 

  o  Built-in commands:

    o   Some built-ins (r, autoload, history, integer ...)
        were aliases in ksh. 
    o   There is no built-in command newgrp: use e.g. `alias
        newgrp="exec newgrp"'
    o   `jobs' has no `-n' flag.
    o   `read' has no `-s' flag.

  o  Other idiosyncrasies:

    o   `select' always redisplays the list of selections on each loop.

2.2: 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:

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

2.3: 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'

  and not

    alias newcmd 'list of commands'

  which won't work. (It tells you if `newcmd' and `list of commands' are
  already defined as aliases.)

  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'

  can be replaced by the zsh function,

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

  (the `builtin' tells zsh to use its own `cd', avoiding an infinite loop)
  or, perhaps better,

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

  (which converts your home directory to a ~).  In fact, this problem is
  better solved by defining the special function chpwd() (see the manual).
  Note also that the `;' at the end of the function is optional in zsh,
  but not in ksh or sh (for sh's where it exists).

  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" 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:

        o  convert all of them to zsh functions; or
        o  after converting, be sure your .zshrc defines all of your
           aliases before it defines any of your functions.

     Those first four are all you really need, but here are four more for
     heavy csh alias junkies:

  5) Mapping from csh alias "parameter referencing" into zsh function
     (assuming SH_WORD_SPLIT and KSH_ARRAYS are NOT set in zsh):

      csh             zsh
     =====         ==========
     \!*           $*              (or $argv)
     \!^           $1              (or $argv[1])
     \!:1          $1
     \!:2          $2              (or $argv[2], etc.)
     \!$           $*[$#]          (or $argv[$#], or $*[-1])
     \!:1-4        $*[1,4]
     \!:1-         $*[1,$#-1]      (or $*[1,-2])
     \!^-          $*[1,$#-1]
     \!*:q         "$@"
     \!*:x         $=*             ($*:x doesn't work (yet))

  6) 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.)

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

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

  8) 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 }

  `l' in the function definition is in command position and is expanded
  as an alias, defining `/bin/ls' and `-F' as functions which call
  `/bin/ls', which gets a bit recursive.  This can be avoided if you use
  `function' to define a function, which doesn't expand aliases.  It is
  possible to argue for extra warnings somewhere in this mess.

  Earlier versions of the FAQ claimed `it is not possible to define
  `function' as an alias'.  This turns out to be false; you can even
  confuse yourself this way.  The point to remember is that aliases are
  quite deliberately a way of subverting the shell's syntax for special
  effects.  If you wish to be completely safe, you should stick with
  functions.

  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.

2.4: 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'

  which pushes the current line onto the stack and tries to bring a job
  with the basename of your editor into the foreground.  `bindkey -s'
  allows limitless possibilities along these lines.  You can execute
  any command in the middle of editing a line in the same way,
  corresponding to tcsh's `-c' option:

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

  In both these examples, the `\eq' saves the current input line to
  be restored after the command runs; a better effect with multiline
  buffers is achieved if you also have

    bindkey '\eq' push-input

  to save the entire buffer.  In 4.0 and recent versions of zsh 3.1, you
  have the following more sophisticated option,

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

  and can now bind run-fg-editor just like any other editor function.

2.5: 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.

2.6: 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.
    http://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.

Chapter 3: How to get various things to work

3.1: 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"

  are split into words when passed to a command or used in a `for foo in
  $var' loop.  By default, zsh does not have that behaviour: the
  variable remains intact.  (This is not a bug!  See below.)  The option
  SH_WORD_SPLIT exists to provide compatibility.

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

    args() { echo $#; }

  and with our definition of `var',

    args $var

  produces the output `1'.  After

    setopt shwordsplit

  the same function produces the output `2', as with sh and ksh.

  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

  (or

    array=(one two three twenty)

  if you prefer), followed by

    args $array

  produces the output `4', regardless of the setting of SH_WORD_SPLIT.
  Arrays are also much more versatile than single strings.  Probably
  if this mechanism had always been available there would never have
  been automatic word splitting in scalars, which is a sort of
  uncontrollable poor man's 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\\'e de bonne heure."
    eval "words=($sentence)"

  after which $words is an array with the words of $sentence (note
  characters special to the shell, such as the `'' in this example,
  must already be quoted), or, less standard but more reliable,
  turning on SH_WORD_SPLIT for one variable only:

    args ${=sentence}

  always returns 8 with the above definition of `args'.  (In older
  versions of zsh, ${=foo} toggled SH_WORD_SPLIT; now it forces it on.)

  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 ksh will create a parameter with value `foo bar', but in zsh will
  create a parameter param with value foo and a parameter bar
  whose value is empty.  Contrast this with a normal assignment (no
  typeset or other command in front), which never causes a word split
  unless you have GLOB_ASSIGN set.  From zsh version 4.0.2 the option
  KSH_TYPESET, set automatically in compatibility mode, fixes this
  problem.  Note that in bash this behaviour occurs with all arguments that
  look like assignments, whatever the command name; to get this behaviour
  in zsh you have to set the option MAGIC_EQUAL_SUBST.

3.2: 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.  All
  login shells are interactive.  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).  

  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.

3.3: 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.

  For these reasons it is usually best to avoid ALL_EXPORT unless you
  have a specific use for it.  One safe use is to set it before
  creating a list of variables in an initialisation file, then unset
  it immediately afterwards.  Only those variables will be automatically
  exported.

3.4: 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'

  You can have both nocorrect and noglob, if you like, but the
  nocorrect must come first, since it is needed by the line editor,
  while noglob is only handled when the command is examined.

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

3.5: How do I get the meta key to work on my xterm?

  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

  or, on SYSVR4-ish systems without pass8,

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

  (disable parity detection, don't strip high bit, use 8-bit characters).
  Make sure this comes _before_ any bindkey entries in your .zshrc which
  redefine keys normally defined in the emacs/vi keymap.  You may also
  need to set the eightBitOutput resource in your ~/.Xdefaults
  file, although this is on by default and it's unlikely anybody will
  have tinkered with it.

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

3.6: 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.

3.7: 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.

3.8: Why do the cursor (arrow) keys not work?

  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

  For most even vaguely VT100-compatible terminals, the above eight
  instructions are a fairly safe bet for your .zshrc.  Of course
  you can substitute variant functions for the second argument here too.

3.9: 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

  before any stty commands you use.

  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

  (in this example).  Note that zsh doesn't reset the terminal completely
  afterwards: just the modes it uses itself and a number of special
  processing characters (see the stty(1) manual page).

3.10: 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

  in your .zshrc should be sufficient.

  Another method is to put

    #!/bin/sh
    TERM=emacs exec zsh

  into a file ~/bin/eshell, then `chmod +x ~/bin/eshell', and
  tell emacs to use that as the shell by adding

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

  to ~/.emacs.

3.11: 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
  compatiblity, 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.)

3.12: How does base arithmetic work?

  The ksh syntax is now understood, i.e.

    let 'foo = 16#ff'

  or equivalently

    (( foo = 16#ff ))

  or even

    foo=$((16#ff))

  The original syntax was

    (( foo = [16]ff ))

  --- this was based on a misunderstanding of the ksh manual page.  It
  still works but its use is deprecated.  Then

    echo $foo

  gives the answer `255'.  It is possible to declare variables explicitly
  to be integers, via

    typeset -i foo

  which has a different effect: namely the base used in the first
  assignment (hexadecimal in the example) is subsequently used whenever
  `foo' is displayed (although the internal representation is unchanged).
  To ensure foo is always displayed in decimal, declare it as

    typeset -i 10 foo

  which requests base 10 for output.  You can change the output base of an
  existing variable in this fashion.  Using the `$(( ... ))' method will
  always display in decimal, except that in 3.1.9 there is a new feature
  for selecting a base for displaying here:

    print $(( [#16] 255 ))

3.13: How do I get a newline in my prompt?

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

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

  If you have the bad taste to set the option cshjunkiequotes, which
  inhibits such behaviour, you will have to bracket this with
  `unsetopt cshjunkiequotes' and `setopt cshjunkiequotes', or put it
  in your .zshrc before the option is set.

  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?%# '

  is a neat way of doing what you want.  Note that it is the quotes, not
  the prompt expansion, which turns the `\n' into a newline.

3.14: 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.

3.15: 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.

3.16: 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

  are a good sign that you tried calling `foo' in function `foo' without
  using `command'.  If `foo' is a builtin rather than an external
  command, use `builtin foo' instead.

3.17: 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 (`setopt cshjunkiehistory' to turn it on).

3.18: 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: `setopt nohup'
  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.

3.19: 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.

3.20: 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

  allowing you to have the COMMANDS delimited with some other command
  structure, often `{...}'.  The rules are quite complicated and
  in most scripts it is probably safer --- and certainly more
  compatible --- to stick with the sh-like rules.  If you are
  wondering, the following is a rough guide.

  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; }

  but this does _not_:

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

  The reason is that after `while', any sort of command list is valid.
  This includes the whole list `let "i++ < 10"; { echo i $i; }';
  the parser simply doesn't know when to stop.  Furthermore, it is
  wrong to miss out the semicolon, as this makes the `{...}' part
  of the argument to `let'.  A newline behaves the same as a
  semicolon, so you can't put the brace on the next line as in C.

  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 }

  but with `for', which only needs a list of words, you can get
  away with it:

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

  since the parser knows it only needs everything up to the first
  semicolon. For the same reason, there is no problem with the `repeat',
  `case' or `select' constructs; in fact, `repeat' doesn't even
  need the semicolon since it knows the repeat count is just one word.

  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.

3.21: 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

  $HISTSIZE tells the shell how many lines to keep internally,
  $HISTFILE tells it where to write the history, and $SAVEHIST,
  the easiest one to forget, tells it how many to write out.  The
  simplest possibility is to set it to the same as $HISTSIZE as
  above.  There are also various options affecting history; see the
  manual.

3.22: 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}

  Ignore the `(e)' for now.  The `:+' means: if the variable
  $E is set, substitute the following, i.e. `\$$E'.  This is
  expanded to `$EDITOR' by the normal rules.  Finally, the `(e)' means
  `evaluate the expression you just made'.  This gives `emacs'.

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

    eval echo \$$E

  produces the same result.

  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.

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

  The problem is, for example,

    % echo -n foo
    % 

  and the foo has been overwritten by the prompt %.  The answer is
  simple:  put unsetopt promptcr in your .zshrc.  The option PROMPT_CR,
  to print a carriage return before a new prompt, is set by default because
  a prompt at the right hand side (`$RPROMPT', `$RPS1') will not appear
  in the right place, and multi-line editing will be confused about the line
  position, unless the line starts in the left hand column.  Apart from
  PROMPT_CR, you can force this to happen by putting a newline in the
  prompt (see question 3.13 for that).

3.24: 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).

3.25: How do I get coloured prompts on my colour xterm?

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

  The `$'' form of quoting turns the ``\e'' into a real escape
  character; this only works from about version 3.1.4, so if you're using
  3.0.x, you need to do something like

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

  The ``%{...%}'' is used in prompts for strings which will
  not appear as characters, so that the prompt code doesn't miscalculate the
  length of the prompt which would have a bad effect on editing.  The
  resulting ``<ESC>[1;31m'' makes the prompt red, and the
  ``<ESC>[0m'' puts printing back to normal so that the rest of the line
  is unchanged.

3.26: 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

  What you're probably expecting is that the command `foo' sends its
  standard output to the pipe and so to the input of the command `bar',
  while it sends its standard error to the file `foo.out'.  What you
  actually see is that the output is going both to the pipe and into the
  file.  To be more explicit, here's the same example with real commands:

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

  and you can see `output' appears twice.

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

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

  You might recognise this as a standard feature of zsh, called `multios'
  and controlled by the option of the same name, whereby output is copied
  to both files when the redirector appears twice.  What's going on in the
  first example is exactly the same, however the second redirector is
  disguised as a pipe.  So if you want to turn this effect off, you need
  to `unsetopt multios'.

3.27: Why am I prompted to correct commands which are in my path?

(Or, if you know about the command hash table, the command isn't in the
table even though you know it works --- it's the same basic problem.)

It occasionally happens that a directory in your path is not readable,
although files in it have `execute' permission.  Then the system can
execute them, but the shell can't see them when it scans the path, since
it does that by trying to read the directory.  If this is the case, you
may find `which var(cmd)' does find the command, since then the
shell checks the path explicitly for that one command rather than
looking for all files in the directory.

Chapter 4: The mysteries of completion

Programmable completion using the `compctl' command is one of the most
powerful, and also potentially confusing, features of zsh; here I give
a short introduction.  There is a set of example completions supplied
with the source in Misc/compctl-examples; completion definitions for
many of the most obvious commands can be found there.

If this confuses you, you may like to know that there is a new, more
elegant completion system which appeared in version 3.1.6.  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.  The rest of this section talks about the
old completion system.

4.1: 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.

4.2: 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 file name 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.

  Other forms of completion have to be set up by special arrangement.
  See the manual entry for compctl for a list of all the flags:  you
  can make commands complete variable names, user names, job names,
  etc., etc.

  For example, one common use is that you have an array variable,
  $hosts, which contains names of other machines you use frequently on
  the network:

    hosts=(fred.ph.ku.ac.uk snuggles.floppy-bunnies.com here.there.edu)

  then you can tell zsh that when you use telnet (or ftp, or ...), the
  argument will be one of those names:

    compctl -k hosts telnet ftp ...

  so that if you type `telnet fr' and hit TAB, the rest of the name
  will appear by itself.

  An even more powerful option to compctl (-g) is to tell zsh that
  only certain sorts of filename are allowed.  The argument to -g is
  exactly like a glob pattern, with the usual wildcards `*', `?', etc.
  In the compctl statement it needs to be quoted to avoid it being
  turned into filenames straight away.  For example,

    compctl -g '*.(ps|eps)' ghostview

  tells zsh that if you type TAB on an argument after a ghostview
  command, only files ending in `.ps' or `.eps' should be considered
  for completion.

  A useful addition for zsh from version 3.1 is directory completion:

    compctl -/ cd

  Before, you had to use -g, but this is neater: it takes care of
  things like ignoring directories beginning with a dot unless you've
  typed the dot yourself, and whole directory paths are understood.

  Note that flags may be combined; if you have more than one, all the
  possible completions for all of them are put into the same list, all
  of them being possible completions.  So

    compctl -k hosts -f rcp

  tells zsh that rcp can have a hostname or a filename after it.  (You
  really need to be able to handle host:file, which is where
  programmable completion comes in, see 4.5.)  Also, from
  version 3.1 you can always handle directories at the same time as
  other files just by adding -/ to the list.

4.3: 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 (use `setopt
  var(optioname)' to turn an option on).  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:

   o  with NO_BEEP set, that annoying beep goes away
   o  with NO_LIST_BEEP, beeping is only turned off for ambiguous
      completions
   o  with AUTO_LIST set, when the completion is ambiguous you get a
      list without having to type \C-D
   o  with BASH_AUTO_LIST set, the list only happens the second
      time you hit tab on an ambiguous completion
   o  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.
   o  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
   o  with AUTO_MENU, you only get the menu behaviour when you hit TAB
      again on the ambiguous completion.
   o  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.

  Combinations of these are possible; for example, AUTO_LIST and
  AUTO_MENU together give an intuitive combination.  Note that
  from version 3.1 LIST_AMBIGUOUS is set by default; if you use
  autolist, you may well want to `unsetopt listambiguous'.

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

  Sometimes you have a word on the command-line (let's stick to file
  names) 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, you can `setopt 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.

  That's not the full story, however.  Sometimes you just want the
  part of the word before the cursor completed.  For example, the word
  is `/usr/loc/b', which you want to complete to `/usr/local/bin'.
  Normally, zsh won't do this in one go because there are two bits
  missing (but see below!), so you need to complete the `/usr/loc'
  on its own first.  For this 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

  then in the example you can move to just after `/usr/loc', hit
  whatever key you've just bound, move to the end, and hit tab.
  (Note that AUTO_REMOVE_SLASH behaviour applies here, see the manual.)

  Even that doesn't exhaust the possibilities.  Included with the
  source distribution is the file Functions/multicomp, a function
  which you can bind as an alternative form of default completion (see
  below for a description of alternative completion), e.g.

    compctl -D -f + -U -Q -K multicomp

  and whole sequences of directories, like `/usr/loc/b' or even
  `/u/l/b' can be completed in one go.  It works best with
  menucompletion if the result is ambiguous.

4.5: How do I get started with programmable completion?

  Finally, the hairiest part of completion.  It is possible to get zsh
  to consider different completions not only for different commands,
  but for different words of the same command, or even to look at
  other words on the command line (for example, if the last word was a
  particular flag) and decide then.

  There are really two sorts of things to worry about.  The simpler is
  alternative completion:  that just means zsh will try one
  alternative, and only if there are no possible completions try the
  next.  For example

    compctl -g '*.ps' + -f lpr

  says that after lpr you'd prefer to find only `.ps' files, so if
  there are any, only those are used, but if there aren't any, any
  old file is a possibility.  You can also have a + with no flags
  after it, which tells zsh that it's to treat the command like any
  other if nothing was found.  That's only really useful if your
  default completion is fancy, i.e. you have done something with
  `compctl -D' to tell zsh how commands which aren't specially handled
  are to have their arguments completed.

  The second sort is the hard one.  Following a `-x', zsh expects that
  the next thing will be some completion code, which is a single
  letter followed by an argument in square brackets.  For example
  `p[1]': `p' is for position, and the argument tells it to look at
  position 1; that says that this completion only applies to the word
  immediately after the command.  You can also say `p[1,3]' which says
  the completion only applies to the word if it's between the first
  and third words, inclusive, after the command, and so on.  See the
  list in the `compctl' manual entry for a list of these conditions:
  some conditions take one argument in the square brackets, some two.
  Usually, negative numeric arguments count backwards from the end
  (for example, `p[-1]' applies to the last word on the line).

  (Note the difference in the ways `+' and `-x' work.  A `+'
  completion will always try and find completions for what's before
  the `+' first; it will only produce a list for what's after if
  the first list was empty.  On the other hand, if a condition for a
  `-x' matches, the appropriate set of completions is always used,
  even if the list of completions produced is empty.)

  The condition is then followed by the flags as usual (as in 4.2),
  and possibly other condition/flag sets following a single -; the
  whole lot ends with a double -- before the command name.  In other
  words, each extended completion section looks like this:

    -x <pattern> <flags>... [ - <pattern> <flags>... ...] --

  Let's look at rcp again: this assumes you've set up $hosts as above.
  This uses the `n[<n>,<string>]' flag, which tells zsh to look for
  the <n>'th occurrence of <string> in the word, ignoring anything up
  to and including that.  We'll use it for completing the bits of
  rcp's `user@host:file' combination.  (Of course, the file name is on
  the local machine, not `host', but let's ignore that; it may still
  be useful.)

    compctl -k hosts -S ':' + -f -x 'n[1,:]' -f - \ 
          'n[1,@]' -k hosts -S ':' -- rcp

  This means: (1) try and complete a hostname (the bit before the
  `+'), if successful add a `:' (-S for suffix); (2) if that fails
  move on to try the code after the `+':  look and see if there is a
  `:' in a word (the `n[1,:]'); if there is, complete filenames
  (-f) after the first of them; (3) otherwise look for an `@' and
  complete hostnames after the first of them (the `n[1,@]'), adding a
  `:' if successful; (4) if all else fails use the `-f' before the
  `-x' and try to complete files.

  So the rules for order are (1) try anything before a `+' before
  anything after it (2) try the conditions after a -x in order until
  one succeeds (3) use the default flags before the -x if none of the
  conditions was true.

  Different conditions can also be combined.  There are three levels
  of this (in decreasing order of precedence):

   1) multiple square brackets after a single condition give
      alternatives:  for example, `s[foo][bar]' says apply the
      completion if the word begins with `foo' or `bar',
   2) spaces between conditions mean both must match:  for example,
      `p[1] s[-]' says this completion only applies for the first word
      after the command and only if it begins with a `-',
   3) commas between conditions mean either can match:  for example,
      `c[-1,-f], s[-f]' means either the previous word (-1 relative to
      the current one) is -f, or the current word begins with -f ---
      useful to use the same completion whether or not the -f has a
      space after it.

  You must be careful to put the whole expression inside quotation
  marks, so that it appears as a single argument to compctl.

  Here's a useless example just to show a general `-x' completion.

    compctl -f -x 'c[-1,-u][-1,-U] p[2], s[-u]' -u - \ 
      'c[-1,-j]' -P % -j -- foobar

  The way to read this is:  for command `foobar', look and see if (((the
  word before the current one is -u) or (the word before the current
  one is -U)) and (the current word is 2)) or (the current word begins
  with -u); if so, try to complete user names.  If the word before
  the current one is -j, insert the prefix `%' before the current word
  if it's not there already and complete job names.  Otherwise, just
  complete file names.

4.6: And if programmable completion isn't good enough?

  ...then your last resort is to write a shell function to do it for
  you.  By combining the `-U' and `-K func' flags you can get
  almost unlimited power.  The `-U' tells zsh that whatever the
  completion produces is to be used, even if it doesn't fit what's
  there already (so that gets deleted when the completion is
  inserted).  The `-K func' tells zsh a function name.  The
  function is passed the part of the word already typed, and can read
  the rest of the line with `read -c'.  It can return a set of
  completions via the `reply' array, and this becomes the set of
  possible completions.  The best way to understand this is to look at
  `multicomp' and other functions supplied with the zsh
  distribution.  Almost certainly, however, you are better off using
  the new completion system for anything complicated.  No further
  upgrades are planned for the old system.

Chapter 5: The future of zsh

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

  Here are some of the more well-known ones, very roughly in
  decreasing order of significance.  Many of these can also be counted
  against differences from ksh in question 2.1; note that this applies
  to the latest beta version and that simple bugs are often fixed
  quite quickly.  There is a file Etc/BUGS in the source distribution
  with more detail.

  o  Parameter expansions using the ${param+word} and ${param-word}
    forms may fail to behave in Bourne-shell-compatible fashion when the
    SH_WORD_SPLIT option is set and the word contains spaces.
  o  `time' is ignored with builtins and can't be used with `{...}'.
  o  `set -x' (`setopt xtrace') still has a few glitches; these
     are mostly fixed in 3.1.6.
  o  Zsh's notion of the current line number (via $LINENO) is
     sometimes not well handled, particularly when using functions and traps.
     This should also work reliably from 3.0.6 and 3.1.6.
  o  In vi mode, `u' can go past the original modification point.
  o  The singlelinezle option has problems with prompts containing escapes.
  o  The `r' command does not work inside `$(...)' or ``...`'
     expansions.   This is fixed in 3.1.
  o  `typeset' handling is non-optimal, particularly with regard to
     flags, and is ksh-incompatible in unpredictable ways.  3.1.6 has
     been overhauled, but remaining glitches are to be expected.
  o  Nested closures in extended globbing and pattern matching, such as

      [[ fofo = (fo#)# ]]

     were once not correctly handled, and there were problems with
     complicated exclusions using `^' or `~'.  These are fixed
     since version 3.1.3.

  o  Handling of the `:q' and `:x' with parameter subsitutions is
    erratic: neither work in any 3.0 release, and :x doesn't work in
    any release so far.

  Note that a few recent changes introduce incompatibilities (these
  are not bugs):

  Changes after zsh 3.0:

  o  The options ALWAYS_LAST_PROMPT (return to the line you were
     editing after displaying completion lists) and LIST_AMBIGUOUS
     (don't do AUTO_LIST if there was an unambiguous prefix that could be
     inserted, i.e. only list if it is ambiguous what to insert next) are
     now set by default.  This is in response to complaints that too many
     zsh features are never noticed by many users.  To turn them off,
     just put `unsetopt alwayslastprompt listambiguous' in your
     .zshrc file.
  o  In 3.1.5, history-search-{forward,backward} only find previous
     lines where the first word is the same as the current one.  For
     example, 

      comp<ESC>p

     will find lines in the history like `comp -edit emacs', but not
     `compress file' any more.  For this reason, `\M-n' and
     `\M-p' use history-beginning-search-{forward,backward} which
     search for a line with the same prefix up to the cursor position.
     From 3.1.6, there is a different implementation which makes this
     closer (though not identical) to the old behaviour, and the
     traditional bindings have been restored.. The story for the 
     {up,down}-line-or-search commands is similar.
  o  In vi insert mode, the cursor keys no longer work.  The following
     will bind them:

       bindkey -M viins '^[[D' vi-backward-char '^[[C' vi-forward-char \ 
                      '^[[A' up-line-or-history '^[[B' down-line-or-history

     (unless your terminal requires `^[O' instead of `^[[').  The
     rationale is that the insert mode and command mode keymaps for
     keys with prefixes are now separate.

  Changes since zsh 2.5:

  o  The left hand of an assignment is no longer substituted.  Thus,
     `$1=$2' will not work.  You can use something like `eval
     "$1=\$2"', which should have the identical effect.
  o  Signal traps established with the `trap' builtin are now called with
     the environment of the caller, as in ksh, instead of as a new
     function level.  Traps established as functions (e.g. `TRAPINT()
     {...}') work as before.
  o  The NO_CLOBBER option is now -C and PRINT_EXIT_VALUE -1; they
     used to be the other way around.  (Use of names rather than letters is
     generally recommended.)
  o  `[[' is a reserved word, hence must be separated from
     other characters by whitespace; `{' and `}' are also reserved
     words if the IGNORE_BRACES option is set.
  o  The option CSH_JUNKIE_PAREN has been removed:  csh-like code now
     always does what it looks like it does, so `if ( ... ) ...'
     executes the code in parentheses in a subshell.  To make this
     useful, the syntax expected after an `if', etc., is less strict
     than in other shells.
  o  `foo=*' does not perform globbing immediately on the right
     hand side of the assignment; the old behaviour now requires the
     option GLOB_ASSIGN.  (`foo=(*)' is and has always been the
     consistent way of doing this.)
  o  <> performs redirection of input and output to the specified file.
     For numeric globs, you now need <->.
  o  The command line qualifiers exec, noglob, command, - are now
     treated more like builtin commands:  previously they were
     syntactically special.  This should make it easier to perform
     tricks with them (disabling, hiding in parameters, etc.).
  o  The pushd builtin has been rewritten for compatibility with other
     shells.  The old behavour can be achieved with a shell function.
  o  The current version now uses ~'s for directory stack substitution
     instead of ='s.  This is for consistency:  all other directory
     substitution (~user, ~name, ~+, ...) used a tilde, while
     =<number> caused problems with =program substitution.
  o  The HISTLIT option was broken in various ways and has been removed:
     the rewritten history mechanism doesn't alter history lines, making
     the option unnecessary.
  o  History expansion is disabled in single-quoted strings, like other
     forms of expansion -- hence exclamation marks there should not be
     backslashed.
  o  The `$HISTCHARS' variable is now `$histchars'.  Currently both
     are tied together for compatibility.
  o  The PROMPT_SUBST option now performs backquote expansion -- hence
     you should quote these in prompts.  (SPROMPT has changed as a result.)
  o  Quoting in prompts has changed: close parentheses inside ternary
     expressions should be quoted with a %; history is now %!, not
     !.  Backslashes are no longer special.

5.2: 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@sunsite.dk

  so mail on any issues (bug reports, suggestions, complaints...)
  related to the development of the shell should be sent there.  If
  you want someone to mail you directly, say so.  Most patches to zsh
  appear there first.

  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@sunsite.dk

  and one just containing announcements:  about releases, about major
  changes in the shell, or this FAQ, for example,

    zsh-announce@sunsite.dk

  (posting to the last one is currently restricted).

  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@sunsite.dk

  (the actual content is unimportant).  Replace subscribe with
  unsubscribe to unsubscribe.  The mailing software (ezlm) has
  various bells and whistles: you can retrieve archived messages.
  Mail zsh-workers-help@sunsite.dk for detailed information.
  Adminstrative matters are best sent to
  zsh-workers-owner@sunsite.dk.  The list maintainer's
  real name is Karsten Thygesen <karthy@kom.auc.dk>.

  An archive of mailings for the last few years can be found at
    http://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.

5.3: What's on the wish-list?

  With version 3, the code is much cleaner than before, but still
  bears the marks of the ages and many things could be done much
  better with a rewrite.  A more efficient set of code for
  lexing/parsing/execution might also be an advantage.  Volunteers are
  particularly welcome for these tasks.

  Here are the latest changes, which appeared in zsh 3.1.6.

  o  Even more powerful new completion system, based on shell functions,
     allowing much more detailed control both over generation of matches
     for completion and how they are inserted and displayed.  A set of
     functions which work `out of the box' will be available, including
     many functions for external commands:  files in tar archives can
     be listed for extraction as if they were real files; GNU commands
     which accept the `--help' option can generate completion lists for
     themselves on the fly, etc., etc.
     You can have old-style compctl-based completions for some commands,
     and new-style ones for others; you can bind particular completion
     commands of your own definition to key-strokes.
  o  Other completion enhancements:  matching control, allowing
     case-insensitive matching and wild card anchors, e.g. `z_t<TAB>'
     can allow a wildcard before the `_' so that this will expand
     to `zle_tricky.c' --- all under user control; completions can
     be grouped; a new completion command, menu-select, allows real menu
     selection --- you can move the cursor around to choose a completion.
  o  Case-insensitive and approximate matching in the globbing code:
     for example, `(#ia2)readme' matches the string `readme'
     case-insensitively with up to two errors, such as README,
     READ.ME, _README_, Read!Me!.  The new completion system
     knows about these, allowing correcting completion, e.g.
     `mkaef<TAB>' can be made to complete to `Makefile'.
  o  Associative arrays, declared with `typeset -A aname'; syntax
     for creating, accessing and deleting elements of these.
  o  Users can create their own foopath/FOOPATH array/path
     combinations, just like path and PATH.
  o  A dynamically loadable library for FTP, complete with a suite of
     functions to make it easy to use.  This allows you to use the shell's
     capabilities for scripting, line editing, completion, I/O redirection,
     directory management etc. within an FTP session.

  Other future possibilities which have been suggested:

  o  The parameter code could do with tidying up, maybe with more of the
     features made available in ksh93.
  o  Configuration files to enable zsh startup files to be created
     with the Dotfile Generator.
  o  Further improvements in integrating the line editor with shell
     functions.
  o  Ksh compatibility could be improved.
  o  Option for glob qualifiers to follow perl syntax (a traditional item).

5.4: Did zsh have problems in the year 2000?

  Not that I heard of; it's up to you to be careful with two-digit dates,
  though, which are produced by the prompt escapes `%W' and `%D',
  and also by the command `print -P'.  Earlier versions of zsh may
  show problems here.

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 and Karsten Thygesen, 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 -- 2001.
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 http://zsh.sunsite.dk/".

User Contributions:

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