
Archive-Name: unix-faq/shell/zsh
Last-Modified: 1997/05/29
Submitted-By: pws@amtp.liv.ac.uk (Peter Stephenson)
Version: $Id: FAQ,v 3.0.2.3 1997/06/02 08:12:41 hzoli Exp $
Frequency: Monthly
Copyright: (C) P.W. Stephenson, 1995, 1996 (see end of document)

Changes since last issue:

1.5:      Latest versions.
1.6:      Mention test versions.

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. What is the difference between `export' and the ALL_EXPORT option?
3.3. How do I turn off spelling correction/globbing for a single command?
3.4. How do I get the meta key to work on my xterm?
3.5. How do I automatically display the directory in my xterm title bar?
3.6. Why does my terminal act funny in some way?
3.7. Why does zsh not work in an Emacs shell mode any more?
3.9. Why do my autoloaded functions not autoload [the first time]?
3.9. How does base arithmetic work?
3.10. How do I get a newline in my prompt?
3.11. Why does `bindkey ^a command-name' or 'stty intr ^-' do something funny?
3.12. Why can't I bind \C-s and \C-q any more?
3.13. How do I execute command `foo' within function `foo'?
3.14. Why do history substitutions with single bangs do something funny?
3.15. Why does zsh kill off all my background jobs when I logout?
3.16. How do I list all my history entries?
3.17. How does the alternative loop syntax, e.g. `while {...} {...}' work?

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 get started with programmable completion?
4.5. 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?

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://www.peak.org/zsh/ (note the change of address from the
  end of April 1997).  The server provides this FAQ and much else and is
  now maintained by Timothy Lumoa.  The FAQ is at http://www.peak.org/zsh/FAQ/ .

  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.  (This article
  also talks about shell startup files which would otherwise rate a
  mention here.)  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.ruu.nl/wais/html/na-dir/unix-faq/shell/.html

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

  (As a method of reading this 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); it's 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 globbing (compctl -g),
    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,
    o  variable, editing function and option name completion,
    o  inline expansion of variables, 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 arithmetic.
  o  Manipulation of arrays (including reverse subscripting).
  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.

  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 config.h.in to configure zsh automatically,
  then send the required context diffs to the list (see question
  5.2).  Changes based on version 2.5 are very unlikely to
  be useful.

  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 make 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 3.0.2 has now been released. The new major number 3.0 largely
  reflects the considerable internal changes in zsh to make it more
  reliable, consistent and (where possible) compatible.  Those
  planning on upgrading their zsh installation should take a look at
  the list of incompatibilities at the end of 5.1.  This is longer
  than usual due to enhanced sh, ksh and POSIX compatibility.
  Version 3.0.3 is currently in test.

  The beta version 3.1.1 has also been released; 3.1.2 is in test.
  Development of zsh is usually 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.

  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 (most recently) to provide POSIX compliancy.

1.6: Where do I get it?

  The archive is now run by Zoltan Hidvegi <hzoli@cs.elte.hu>.  The
  following are known mirrors (kept frequently up to date); the first
  is the official archive site.  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.

    Hungary   ftp://ftp.cs.elte.hu/pub/zsh/
              (also http://www.cs.elte.hu/pub/zsh/ )
    Australia ftp://ftp.ips.gov.au/mirror/zsh/
    Finland   ftp://ftp.funet.fi/pub/unix/shells/zsh/
    France    ftp://ftp.cenatls.cena.dgac.fr/pub/shells/zsh/
    Germany   ftp://ftp.fu-berlin.de/pub/unix/shells/zsh/
              ftp://ftp.gmd.de/packages/zsh/
              ftp://ftp.uni-trier.de/pub/unix/shell/zsh/
    Japan     ftp://ftp.tohoku.ac.jp/mirror/zsh/
              ftp://ftp.nis.co.jp/pub/shells/zsh/
    Norway    ftp://ftp.uit.no/pub/unix/shells/zsh/
    Slovenia  ftp://ftp.siol.net/pub/unix/shells/zsh/
    Sweden    ftp://ftp.lysator.liu.se/pub/unix/zsh/
    UK        ftp://ftp.net.lut.ac.uk/zsh/
              (also by FSP at port 21)
    USA       ftp://ftp.math.gatech.edu/pub/zsh/
              ftp://uiarchive.uiuc.edu/pub/packages/shells/zsh/
              ftp://ftp.sterling.com/zsh/
              ftp://ftp.rge.com/pub/shells/zsh/

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:

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

  or 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. 

  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

  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 with 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 --- 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 commands
     `emulate sh; setopt localoptions' in a shell function will
     turn on sh emulation for that function only.

  The classic difference is word splitting, discussed in 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_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 and 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.
        The KSH_ARRAYS option is now available.
    o   Coprocesses are established by `coproc'; `|&' behaves like
        csh. 

  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.
        (GLOB_SUBST has been added to fix this.)
    o   The backslash in $(echo '\$x') is treated differently:  in ksh,  it
        is not stripped, in zsh it is.  (The `...` form gives the same in
        both shells.)
    o * $PSn do not do parameter substitution by default (use PROMPT_SUBST).
    o   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.

      [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  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  Traps and signals:

    o   Traps are not local to functions.
    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.
    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   In `let "i = foo"', foo is evaluated as a number, not an
        expression (although in `let "i = $foo"' +it is treated as an
        expression). 

  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 shwordsplit and ksharrays 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         "$@"            ($*:q doesn't work (yet))
     \!*: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.  Luckily,
  it is not possible to define `function' as an alias.

  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,
  $histlit, 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.

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.

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.

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.)  An option
  (shwordsplit) 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 shwordsplit.
  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 shwordsplit for one variable only:

    args ${=sentence}

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

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

3.2: 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.

3.3: 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.

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

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

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

  chpwd() {
    [[ -t 1 ]] || return
    case $TERM in
      sun-cmd) print -Pn "\e]l%~\e\\"
        ;;
      xterm) 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.

3.6: 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).

  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), or just export STTY for all commands to see.  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).

  At some point there may be an overhaul which allows the terminal
  modes used by the shell to be modified separately from those seen by
  external programmes.  This is partially implemented already: from 2.5,
  the shell is less susceptible to mode changes inherited from
  programmes than it used to be.

3.7: 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" "~/bin/eshell")

  to ~/.emacs.

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

  (Before version 3.0, autoloading in the Korn shell way was not
  allowed; this article is now a historical artefact and will
  eventually be removed.  Note, however, that the old form of
  autoloading is still allowed and there are no plans to remove it.)

  When you put a shell function in an autoload directory (i.e. one
  mentioned in $FPATH), it should be written just as if it were a
  shell script.  In other words, there should be no line at the
  beginning saying `function foo {' or `foo () {', and consequently
  no matching `}' at the end.  If you include those, then the first
  time you try to use the function, the _whole_ file is run --- in other
  words, zsh simply defines the function and does nothing else.

  As a concrete example, if you have a function which you would define
  on the command line as `xhead () { print -n "\033]2;$*\a"; }' and
  your have assigned `FPATH=~/fns', then your .zshrc should contain
  `autoload xhead' and the file ~/fns/xhead should contain only
  `print -n "\033]2;$*\a"'.  (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.)

3.9: 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]

  (note that `foo=$((16#ff))' is now supported).  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.

3.10: 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.

  Arguably the prompt code should handle `print'-like escapes.  Feel
  free to write this :-).  Otherwise, you can use

    PROMPT=$(print "Hi Joe,\nwhat now?%# ")

  in your initialisation file.

3.11: 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.

3.12: 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 .zshrc.

3.13: 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.

3.14: 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.

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

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

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

3.16: 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.

3.17: 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.

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.

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 comman, 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.

  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 4.4.)

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.  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 your 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 nobeep set, that annoying beep goes away
   o  with nolistbeep, beeping is only turned off for ambiguous completions
   o  with autolist set, when the completion is ambiguous you get a
      list without having to type \C-D
   o  with listambigous, this is modified so that nothing is listed if
      there is an unambiguous prefix or suffix to be inserted
   o  with menucomplete 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 automenu, you only get the menu behaviour when you hit TAB
      again on the ambiguous completion.

  Combinations of these are possible; for example, autolist and
  automenu together give an intuitive combination. 

4.4: 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).

  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.

  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.

4.5: 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 what's on
  the line already, but it can return anything it likes 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.

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  Special variables won't be unset after e.g. `PATH=... read ...',
     i.e. if used with a builtin command or shell function.
     (According to POSIX, this is not a bug with `special' builtins.)
  o  `time' is ignored with builtins and can't be used with `{...}'.
  o  `set -x' (`setopt xtrace') still has a few glitches.
  o  The `:q' and `:x' modifiers don't work for variables.
  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. 
  o  `typeset' handling is non-optimal, particularly with regard to
     flags, and is ksh-incompatible in unpredictable ways. 

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

  Changes after zsh 3.0 (3.1.x is still currently in beta):

  o  history-search-{forward,backward} (bound to \M-n, \M-p)
     now 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 an approximation to the old
     behaviour, use history-beginning-search-{forward,backward} which
     search for a line with the same prefix up to the cursor position.
  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, instead of as a new function level,
     as in ksh.  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  On the other hand, `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@math.gatech.edu

  so any suggestions, complaints, questions and matters for discussion
  should be sent there.  If you want someone to mail you directly, say
  so.  Most patches to zsh appear there first.

  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@math.gatech.edu

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

    zsh-announce@math.gatech.edu

  (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-request@math.gatech.edu

  with the *subject* line (this is a change from the old list)

    subscribe <your-email-address>

  e.g.

    Subject:  subscribe P.Stephenson@swansea.ac.uk

  and you can unsubscribe in the same way.
  The list maintainer, Richard Coleman, can be reached at
  coleman@math.gatech.edu.

  The list from May 1992 to May 1995 is archived in
    ftp://ftp.sterling.com/zsh/zsh-list/YY-MM
  where YY-MM are the year and month in digits.

  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.

  An improved line editor, with user-definable functions and binding
  of multiple functions to keystrokes, is being developed.

  o  Loadable module support (will be in 3.1 but much work still needs doing).
  o  Ksh compatibility could be improved.
  o  Option for glob qualifiers to follow perl syntax (now a traditional item).
  o  Binding of shell functions (or commands?) to key strokes --
     requires some way of accessing the editing buffer from functions
     and probably of executing zle functions as a command.
  o  Users should be able to create their own foopath/FOOPATH array/path
     combinations.

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 and Zoltan Hidvegi, and the
mailing list has been run by Peter Gray, Rick Ohnemus and Richard
Coleman, all of whom deserve thanks.  The world is eternally in the
debt of Paul Falstad for inventing zsh in the first place (though the
wizzo extended completion is by Sven Wischnowsky).

Copyright Information:

This document is copyright (C) P.W. Stephenson, 1995, 1996, 1997. 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://www.peak.org/zsh/".
