mailto(pws@pwstephenson.fsnet.co.uk)\
whentxt(notableofcontents())\
COMMENT(-- mytt is like tt but adds quotes `like this' for plain text --)\
def(mytt)(1)(\
  whentxt(`ARG1')\
  whenhtml(tt(ARG1))\
  whenlatex(tt(ARG1))\
  whenms(tt(ARG1))\
  whensgml(tt(ARG1)))\
COMMENT(-- mybf/em are like bf/em but add *emphasis* for text too --)\
def(mybf)(1)(\
  whentxt(*ARG1*)\
  whenhtml(bf(ARG1))\
  whenlatex(bf(ARG1))\
  whenms(bf(ARG1))\
  whensgml(bf(ARG1)))\
def(myem)(1)(\
  whentxt(_ARG1_)\
  whenhtml(em(ARG1))\
  whenlatex(em(ARG1))\
  whenms(em(ARG1))\
  whensgml(em(ARG1)))\
COMMENT(-- mydit is like dit but no `o' for text mode --)\
def(mydit)(1)(\
    whenlatex(dit(ARG1))\
    whenhtml(dit(ARG1))\
    whentxt(ARG1)\
    whenman(dit(ARG1))\
    whenms(dit(ARG1))\
    whensgml(dit(ARG1)))\
COMMENT(-- myeit is like eit but fancier text formatting --)\
def(myeit)(0)(\
    whenlatex(eit())whenhtml(eit())whenman(eit())whenms(eit())whensgml(eit())\
    whentxt(eit()CHAR(41)))\
def(myeitd)(0)(\
    whenlatex(eit())whenhtml(eit())whenman(eit())whenms(eit())whensgml(eit())\
    whentxt(.))\
COMMENT(-- don't want headers for text --)\
def(myreport)(3)(\
whentxt(report()()())\
whenhtml(report(ARG1)(ARG2)(ARG3))\
whenlatex(report(ARG1)(ARG2)(ARG3))\
whenman(report(ARG1)(ARG2)(ARG3))\
whenms(report(ARG1)(ARG2)(ARG3))\
whensgml(report(ARG1)(ARG2)(ARG3)))\
def(startitem)(0)() \
def(enditem)(0)()\
def(item)(2)(
ARG1: ARG2)\
def(nofill)(1)(ARG1)\
def(uref)(1)(url(ARG1)(ARG1))\
COMMENT(TODO: make this expand to a Unicode em dash (U+2014) in HTML output)\
def(emdash)(0)(\
    whenlatex(---)\
    whenhtml(---)\
    whenman(--)whenms(--)whensgml(--)\
    whentxt(--))\
SUBST(_LPAR_)(CHAR(40))\
SUBST(_RPAR_)(CHAR(41))
COMMENT(-- preserve the indent of the 1st line of paragraph --)\
IFDEF(txt)(\
  DEFINESYMBOL(XXparagraph)()\
  PUSHMACRO(PARAGRAPH)(0)(SYMBOLVALUE(XXparagraph))\
)()
myreport(Z-Shell Frequently-Asked Questions)(Peter Stephenson)(2010/02/15)

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
shells for interactive use.

If you have never heard of mytt(sh), mytt(csh) or mytt(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 link(1.6)(16); if you want to know what to do with
insoluble problems, go to link(6.2)(62).

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

COMMENT(-- need to do this specially in text since it should go here --)
whentxt(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?
2.7. What is zsh's support for Unicode/UTF-8?
2.8. Why does my bash script report an error when I run it under zsh?
2.9. What is a `namespace' anyway?
2.10. What about named references?
2.11. What is zsh's support for non-forking command substitution?
2.12. Comparisons of forking and non-forking command substitution

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?  (And other terminal oddities.)
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. mytt(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 `tt(foo 2>&1 >foo.out | bar)'?
3.27. What are these `^' and `~' pattern characters, anyway?
3.28. How do I edit the input buffer in $EDITOR?
3.29. Why does `which' output for missing commands go to stdout?
3.30. Why doesn't the expansion mytt(*.{tex,aux,pdf}) do what I expect?

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

Chapter 5:  Multibyte input and output

5.1. What is multibyte input?
5.2. How does zsh handle multibyte input and output?
5.3. How do I ensure multibyte input and output work on my system?
5.4. How can I input characters that aren't on my keyboard?

Chapter 6:  The future of zsh
6.1. What bugs are currently known and unfixed? (Plus recent important changes)
6.2. Where do I report bugs, get more info / who's working on zsh?
6.3. What's on the wish-list?
6.4. Did zsh have problems in the year 2000?
6.5. When reporting a bug, how do I reduce my mytt(.zshrc) into a minimal reproduction recipe?

Acknowledgments

Copyright
--- End of Contents ---
)\

chapter(Introducing zsh and how to install it)

sect(Sources of information)
label(11)

  Information on zsh is available via the World Wide Web.  The URL
  is url(https://zsh.sourceforge.io/)(https://zsh.sourceforge.io/) .
  The server provides this FAQ and much else and is
  now maintained by the zsh workers (email email(zsh-workers@zsh.org)).
  The FAQ is at \
url(https://zsh.sourceforge.io/FAQ/)(https://zsh.sourceforge.io/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
  url(https://zsh.sourceforge.io/FAQ/zshfaq.yo)
(https://zsh.sourceforge.io/FAQ/zshfaq.yo) and the plain text version
  can be found at url(https://zsh.sourceforge.io/FAQ/zshfaq.txt)
(https://zsh.sourceforge.io/FAQ/zshfaq.txt) .

  You can also get it via email by emailing \
email(mail-server@rtfm.mit.edu)
  with, in the body of the message, mytt(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 link(1.6)(16).

  I have put together a user guide to complement the manual by
  explaining the most useful features of zsh in a more easy to read way.
  This can be found at the zsh web site:
    url(https://zsh.sourceforge.io/Guide/)(https://zsh.sourceforge.io/Guide/)

  (As a method of reading the following in Emacs, you can type tt(\M-2
  \C-x $) to make all the indented text vanish, then tt(\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 link(6.2)(62).

sect(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 link(6.2)(62)).  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.

sect(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).

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

sect(On what machines will it run?)

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

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

  If you need to change something to support a new machine, it would be
  appreciated if you could add any necessary preprocessor code and
  alter configure.in and acconfig.h to configure zsh automatically,
  then send the required unified diffs to the list (see question
  link(6.2)(62)).  Please make sure you have the latest version first.

  To get it to work, retrieve the source distribution (see question
  link(1.6)(16)), un-gzip it, un-tar it and read the INSTALL file in the top
  directory.  Also read the MACHINES file for up-to-date
  information on compilation on certain architectures.

  mybf(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.

sect(What's the latest version?)

  Zsh 5.9 is the latest production version.  For details of all the
  changes, see the NEWS file in the source distribution.

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

  Note also that as the shell changes, it may become incompatible with
  older versions; see the end of question link(6.1)(61) 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 compliance.

sect(Where do I get it?)
label(16)

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

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

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

  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
  link(1.1)(11)) at:

  description(
    mydit()        url(https://zsh.sourceforge.io/Patches/)
(https://zsh.sourceforge.io/Patches/)
  )

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

  Unfortunately, on many machines you can't use mytt(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 mytt(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 mytt(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
  mytt(exec) is often rather unforgiving. 

  If you have zsh in a subdirectory mytt(bin) of your home directory,
  put this in .profile:
  verb(
    [ -f $HOME/bin/zsh ] && exec $HOME/bin/zsh -l
  )
  or if your login shell is csh or tcsh, put this in .login:
  verb(
    if ( -f ~/bin/zsh ) exec ~/bin/zsh -l
  )
  (in each case the mytt(-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:
  verb(
    [ -f $HOME/bin/zsh ] && {
            echo "Type Y to run zsh: \c"
            read line
            [ "$line" = Y ] && exec $HOME/bin/zsh -l
    }
  )
  and for C-shell-like shells:
  verb(
    if ( -f ~/bin/zsh ) then
            echo -n "Type Y to run zsh: "
            if ( "$<" == 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 mytt(if ($?prompt) exec
  zsh).

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

sect(Differences from sh and ksh)
label(21)

  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:
  enumeration(
  myeit() 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;
  myeit() 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 mytt(ARGV0=sh zsh) will also work);
  myeit() 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;
  myeit() 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;
  myeit() also from 3.0, the command `emulate' is available: `emulate
     ksh' and `emulate sh' set various options as well as changing the
     effect of single-letter option flags as if the shell had been
     invoked with the appropriate name.  Including the command
     `emulate sh; setopt localoptions' in a shell function will
     turn on sh emulation for that function only.  In version 4 (and in
     3.0.6 through 8), this can be abbreviated as `emulate -L sh';
  myeit() in versions after 5.9, the myem(namespace) syntax and
     myem(named references) (ksh mytt(nameref)) are available, but
     differ in some details from the ksh93+ semantics;
  myeit() also after 5.9, myem(non-forking command substitutions) are
     available.  These are described by ksh as myem(a brace group preceded
     by a dollar sign) (mytt(${ list;})), but zsh has both some added
     features adopted from mksh, and some limitations, see link(2.11)(211)
   )

  The classic difference is word splitting, discussed in question \
link(3.1)(31);
  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
  tt(SH_WORD_SPLIT) for backward compatibility.  The next most classic
  difference is that unmatched glob patterns cause the command to abort;
  set tt(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 tt(GLOB_SUBST), tt(IGNORE_BRACES) (though brace expansion occurs
  in some versions of ksh), tt(KSH_ARRAYS), tt(KSH_GLOB), tt(KSH_OPTION_PRINT),
  tt(LOCAL_OPTIONS), tt(NO_BAD_PATTERN), tt(NO_BANG_HIST), tt(NO_EQUALS), \
tt(NO_HUP),
  tt(NO_NOMATCH), tt(NO_RCS), tt(NO_SHORT_LOOPS), tt(PROMPT_SUBST), \
tt(RM_STAR_SILENT),
  tt(POSIX_ALIASES), tt(POSIX_BUILTINS), tt(POSIX_IDENTIFIERS),
  tt(SH_FILE_EXPANSION), tt(SH_GLOB), tt(SH_OPTION_LETTERS),
  tt(SH_WORD_SPLIT) (see question link(3.1)(31)) and tt(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. 

  itemization(
  it() Syntax:
  itemization(
    it()* Shell word splitting: see question link(3.1)(31).
    it()* Arrays are (by default) more csh-like than ksh-like:
        subscripts start at 1, not 0; tt(array[0]) refers to tt(array[1]);
        mytt($array) refers to the whole array, not tt($array[0]);
        braces are unnecessary: tt($a[1] == ${a[1]}), etc.
        Set the tt(KSH_ARRAYS) option for compatibility.
    it()  Furthermore, individual elements of arrays in zsh are always
        strings, not separate parameters.  This means, for example, you
	can't `unset' an array element in zsh as you can in ksh; you
	can only set it to the empty string, or shorten the array.
	(You can unset elements of associative arrays in zsh because
	those are a completely different type of object.)
    it()  Coprocesses are established by mytt(coproc); mytt(|&) behaves like
        csh.  Handling of coprocess file descriptors is also different.
    it()  In mytt(cmd1 && cmd2 &), instead of backgrounding the whole
        expression, only mytt(cmd2) is run in the background in zsh.
        Use mytt(( cmd1 && cmd2 ) &) as a workaround.
  )
  it() Command line substitutions, globbing etc.:
  itemization(
    it()* Failure to match a globbing pattern causes an error (use
        tt(NO_NOMATCH)).
    it()* The results of parameter substitutions are treated as plain text:
        mytt(foo="*"; print $foo) prints all files in ksh but mytt(*) in zsh
        (use tt(GLOB_SUBST)).
    it()* tt($PSn) do not do parameter substitution by default (use \
PROMPT_SUBST).
    it()* Standard globbing does not allow ksh-style `pattern-lists'.
        Equivalents:
  verb(
----------------------------------------------------------------------
      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 mytt(^), mytt(~) and mytt(#) (but not mytt(|))forms require \
tt(EXTENDED_GLOB).
      From version 3.1.3, the ksh forms are fully supported when the
      option tt(KSH_GLOB) is in effect; for previous versions you
      must use the table above.

      [1] See question link(3.27)(327) for more on the mysteries of
        mytt(~) and mytt(^).
    it()  Unquoted assignments do file expansion after mytt(:)s (intended for
        PATHs). 
    it()* mytt(typeset) and mytt(integer) have special behaviour for
        assignments in ksh, but not in zsh.  For example, this doesn't
        work in zsh:
  verb(
          integer k=$(wc -l ~/.zshrc)
      )
        because the return value from tt(wc) includes leading
        whitespace which causes wordsplitting.  Ksh handles the
        assignment specially as a single word.
  )
  it() Command execution:
  itemization(
    it()* There is no tt($ENV) variable (use tt(/etc/zshrc), tt(~/.zshrc); 
        note also tt($ZDOTDIR)).
    it()* tt($PATH) is not searched for commands specified
        at invocation without -c.
  )
  it() Aliases and functions:
  itemization(
    it()  The order in which aliases and functions are defined is significant:
        function definitions with () expand aliases -- see question \
link(2.3)(23).
    it()  Aliases and functions cannot be exported.
    it()  There are no tracked aliases: command hashing replaces these.
    it()  The use of aliases for key bindings is replaced by `bindkey'.
    it()* 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).
    it()  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.
  )
    it() Traps and signals:
  itemization(
    it()* Traps are not local to functions.  The option LOCAL_TRAPS is
          available from 3.1.6.
    it()  TRAPERR has become TRAPZERR (this was forced by UNICOS which
        has SIGERR).
  )
  it() Editing:
  itemization(
    it()  The options tt(gmacs), tt(viraw) are not supported.
        Use bindkey to change the editing behaviour: mytt(set -o {emacs,vi})
        becomes `bindkey -{e,v}', although `set -o emacs' and `set -o vi'
        are supported for compatibility; for gmacs, go to emacs mode and
        use `bindkey \^t gosmacs-transpose-characters'.
    it()  The mytt(keyword) option does not exist and mytt(-k) is instead
        interactivecomments.  (mytt(keyword) is not in recent versions
        of ksh either.)
    it()* Management of histories in multiple shells is different:
        the history list is not saved and restored after each command.
        The option tt(SHARE_HISTORY) appeared in 3.1.6 and is set in ksh
        compatibility mode to remedy this.
    it()  mytt(\) does not escape editing chars (use mytt(^V)).
    it()  Not all ksh bindings are set (e.g. mytt(<ESC>#); try mytt(<ESC>q)).
    it()* mytt(#) in an interactive shell is not treated as a comment by
        default.
    it()  In vi command mode the keys "k" and "j" move the cursor to the
        end of the line.  To move the cursor to the start instead, use
  verb(
          bindkey -M vicmd 'k' vi-up-line-or-history
          bindkey -M vicmd 'j' vi-down-line-or-history
  )
  )
  it() Built-in commands:
  itemization(
    it()  Some built-ins (tt(r), tt(autoload), tt(history), tt(integer) ...)
        were aliases in ksh. 
    it()  There is no built-in command newgrp: use e.g. mytt(alias
        newgrp="exec newgrp")
    it()  mytt(jobs) has no mytt(-n) flag.
  )
  it() Other idiosyncrasies:
  itemization(
    it()  mytt(select) always redisplays the list of selections on each loop.
  )
  )

sect(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:
  itemization(
  it()  tt(logout), tt(rehash), tt(source), tt((un)limit) built-in commands.
  it()  tt(*rc) file for interactive shells.
  it()  Directory stacks.
  it()  tt(cshjunkie*), tt(ignoreeof) options.
  it()  The tt(CSH_NULL_GLOB) option.
  it()  tt(>&), tt(|&) etc. redirection.
      (Note that mytt(>file 2>&1) is the standard Bourne shell command for
      csh's mytt(>&file).)
  it()  tt(foreach ...) loops; alternative syntax for other loops.
  it()  Alternative syntax mytt(if ( ... ) ...), though this still doesn't
      work like csh: it expects a command in the parentheses.  Also
      mytt(for), mytt(which).
  it()  tt($PROMPT) as well as tt($PS1), tt($status) as well as tt($?),
      tt($#argv) as well as tt($#), .... 
  it()  Escape sequences via tt(%) for prompts.
  it()  Special array variables tt($PATH) etc. are colon-separated, tt($path)
      are arrays.
  it()  tt(!)-type history (which may be turned off via mytt(setopt
      nobanghist)).
  it()  Arrays have csh-like features (see under link(2.1)(21)).
  )

sect(Why do my csh aliases not work?  (Plus other alias pitfalls.))
label(23)

  First of all, check you are using the syntax
  verb(
    alias newcmd='list of commands'
  )
  and not
  verb(
    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 mytt(\!*), 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
  verb(
    alias cd 'cd \!*; echo $cwd'
  )
  can be replaced by the zsh function,
  verb(
    cd() { builtin cd "$@"; echo $PWD; }
  )
  (the `builtin' tells zsh to use its own `cd', avoiding an infinite loop)
  or, perhaps better,
  verb(
    cd() { builtin cd "$@"; print -D $PWD; }
  )
  (which converts your home directory to a tt(~)).  In fact, this problem is
  better solved by defining the special function chpwd+_LPAR__RPAR_ (see
  the manual). Note also that the mytt(;) 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.

  enumeration(
  myeit() If the csh alias references "parameters" (tt(\!:1), tt(\!*) etc.),
     then in zsh you need a function (referencing tt($1), tt($*) etc.).
     In recent versions of zsh this can be done by defining an anonymous
     function within the alias.  Otherwise, a simple zsh alias suffices.

  myeit() If you use a zsh function, you need to refer _at_least_ to
     tt($*) in the body (inside the tt({ })).  Parameters don't magically
     appear inside the tt({ }) the way they get appended to an alias.

  myeit() If the csh alias references its own name (tt(alias rm "rm -i")),
     then in a zsh function you need the "command" or "builtin" keyword
     (function tt(rm() { command rm -i "$@" })), but in a zsh alias
     you don't (tt(alias rm="rm -i")).

  myeit() If you have aliases that refer to each other (tt(alias ls "ls -C";
     alias lf "ls -F" ==> lf == ls -C -F)) then you must either:
  itemization(
        it() convert all of them to zsh functions; or
        it() 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:

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

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

  myeit() To begin a zsh alias with a - (dash, hyphen) character, use
     mytt(alias --):
      verb(
             csh                            zsh
        ===============             ==================
        alias - "fg %-"             alias -- -="fg %-"
      )

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

  There is one other serious problem with aliases: consider
  verb(
    alias l='/bin/ls -F'
    l() { /bin/ls -la "$@" | more }
  )
  mytt(l) in the function definition is in command position and is expanded
  as an alias, defining mytt(/bin/ls) and mytt(-F) as functions which call
  mytt(/bin/ls), which gets a bit recursive.  Recent versions of zsh treat
  this as an error, but older versions silently create the functions.

  One workaround for this is to use the "function" keyword instead:
  verb(
    alias l='/bin/ls -F'
    function l { /bin/ls -la "$@" | more }
  )
  The mytt(l) after mytt(function) is not expanded.  Note you don't need
  the mytt(_LPAR__RPAR_) in this case, although it's harmless.

  You need to be careful if you are defining a function with multiple
  names; most people don't need to do this, so it's an unusual problem,
  but in case you do you should be aware that in versions of the shell
  before 5.1 names after the first em(were) expanded:
  verb(
    function a b c { ... }
  )
  Here, mytt(b) and mytt(c), but not mytt(a), have aliases expanded.
  This oddity was fixed in version 5.1.

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

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

  If you aware of the problem, you can always escape part or all of the
  name of the function:
  verb(
     'l'() { /bin/ls -la "$@" | more }
  )
  Adding the quotes has no effect on the function definition, but
  suppresses alias expansion for the function name.  Hence this is
  guaranteed to be safe---unless you are in the habit of defining
  aliases for expressions such as tt('l'), which is valid, but probably
  confusing.

sect(Similarities with tcsh)

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

  If you're missing the editor function tt(run-fg-editor), try something
  with mytt(bindkey -s) (which binds a string to a keystroke), e.g.
  verb(
    bindkey -s '^z' '\eqfg %$EDITOR:t\n'
  )
  which pushes the current line onto the stack and tries to bring a job
  with the basename of your editor into the foreground.  mytt(bindkey -s)
  allows limitless possibilities along these lines.  You can execute
  any command in the middle of editing a line in the same way,
  corresponding to tcsh's mytt(-c) option:
  verb(
    bindkey -s '^p' '\eqpwd\n'
  )
  In both these examples, the mytt(\eq) saves the current input line to
  be restored after the command runs; a better effect with multiline
  buffers is achieved if you also have
  verb(
    bindkey '\eq' push-input
  )
  to save the entire buffer.  In version 4 and recent versions of zsh 3.1,
  you have the following more sophisticated option,
  verb(
    run-fg-editor() {
      zle push-input
      BUFFER="fg %$EDITOR:t"
      zle accept-line
    }
    zle -N run-fg-editor
  )
  and can now bind tt(run-fg-editor) just like any other editor function.

sect(Similarities with bash)
label(25)

  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 compliance
  (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 `tt(${var/old/new})'
  feature for replacing the text tt(old) with the text tt(new) in the
  parameter tt($var).  Note one difference here:  while both shells
  implement the syntax `tt(${var/#old/new})' and `tt(${var/%old/new})' for
  anchoring the match of tt(old) to the start or end of the parameter text,
  respectively, in zsh you can't put the `tt(#)' or `tt(%)' inside a
  parameter:  in other words `tt({var/$old/new})' where tt(old) begins with
  a `tt(#)' 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, `tt((#s))' to match the start of a string,
  and `tt((#e))' to match the end.  These require the option
  tt(EXTENDED_GLOB) to be set.

sect(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
  tt(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 (search for tt(csh-whynot)
  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.

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

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

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

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

sect(Why does my bash script report an error when I run it under zsh?)
label(28)

  em(tl;dr:) bash is not the reference implementation of zsh, and zsh is not
  a bug-for-bug compatible reimplementation of bash.

  bash and zsh are different programming languages.  They are not
  interchangeable; programs written for either of these languages will,
  in general, not run under the other.  (The situation is similar with
  many other pairs of closely-related languages, such as Python 2 and
  Python 3; C and C++; and even C89 and C11.)

  When bash and zsh behave differently on the same input, whether zsh's
  behaviour is a bug does not depend on what bash does on the same
  input; rather, it depends on what zsh's user manual specifies.
  (By way of comparison, it's not a bug in Emacs that mytt(:q!) doesn't
  cause it to exit.)

  That being said, the bash and zsh languages do have a common subset, and it is
  feasible to write non-trivial pieces of code that would run under either of
  them, if one is sufficiently familiar with both of them.  However,
  a difference between bash's behaviour and zsh's does not imply that
  zsh has a bug.  The difference might be a bug in zsh, a bug in bash, or
  a bug in neither shell
  (see link(3.1)(31) for an example).

  The recommended way to deal with these differences depends on what kind
  of piece of code is in question: a myem(script) or a myem(plugin).
  
  For em(scripts) emdash() external commands that
  are located in tt($PATH), or located elsewhere and are executed by
  giving their path explicitly (as in mytt(ls), mytt(/etc/rc.d/sshd),
  and mytt(./configure)) emdash() the answer is simple:

  Don't run bash scripts under zsh.  If the scripts were written for
  bash, run them in bash.  There's absolutely no problem with having
  mytt(#!/usr/bin/env bash) scripts even if mytt(zsh) is your shell for
  interactive sessions.
  
  In fact, if you've recently changed to zsh, we myem(recommend) that
  you keep your scripts as mytt(#!/usr/bin/env bash), at least for
  a while: this would make the change more gradual and flatten your
  learning curve.  Once you're used to zsh, you can decide for each
  script whether to port it to zsh or keep it as-is.

  For myem(plugins) emdash() pieces of code
  executed within the shell itself, loaded via the mytt(.),
  mytt(source), or mytt(autoload) builtins, added to mytt(.zshrc), or
  pasted interactively at the shell prompt emdash() one may consider it
  worthwhile to invest the effort to make them runnable under either shell.
  However, as mentioned above, doing so requires one to be familiar with both
  shells, and either steer clear of their differences or handle them explicitly
  with conditional code (such as mytt(if test -n "$ZSH_VERSION")).

  In summary,
  if you'd like to run a bash script or plugin under zsh, you must port the script or plugin
  properly, reviewing it line by line for differences between the two
  languages and adjusting it accordingly, just like you would
  when translating a book from American English to British English.

sect(What is a mytt(namespace) anyway?)
label(29)

  As of this writing, namespaces in zsh are little more than syntactic
  sugar for grouping related parameters.  For example, as of the update
  to PCRE2, the parameters ${.pcre.match} and ${.pcre.subject} are used
  for regular expression substring capture.  The mytt(.pcre.) part is
  the namespace, and when you refer to a parameter that has one, you
  mybf(must) use the mytt(${...}) braces around the name.  Assignments
  are not special, they have the form mytt(.nspace.var=value) as usual.

  Parameters using a namespace have the additional property that, like
  file names beginning with a dot for globbing, they're hidden from
  mytt(typeset) output unless explicitly asked for.

  Namespaces appear in releases after but not including zsh 5.9.

sect(What about named references?)
label(210)

  Named references are a bit like aliases, but for parameters.  A named
  reference would typically be usable in the same cases as ${(P)name}
  (see link(3.22)(322)).  The value of a named reference is the name
  of another parameter, and when you expand or assign to the named
  reference, that other parameter is expanded or assigned instead.
  Thus a trivial example is
  verb(
    % target=RING
    % typeset -n ref=target
    % print $ref
    RING
    % ref=BULLSEYE
    % print $target
    BULLSEYE
  )

  One exception to this behavior is when a named reference is used as
  the loop variable in a mytt(for) loop.  In that case the reference is
  unset and reset on each iteration of the loop.
  verb(
    % target=RING bullseye=SPOT other=MISS
    % typeset -n ref=other
    % for ref in target bullseye; do
    > print $ref
    > ref=HIT:$ref
    > done
    RING
    SPOT
    % print $other
    MISS
    % print $ref
    HIT:SPOT
  )

  Named references may be used in zsh versions later than 5.9.

sect(What is zsh's support for non-forking command substitution?)
label(211)

  This is for cases where you'd write mytt($(command)) but you don't want
  the overhead or other issues associated with forking a subshell.
  There are 3 variations:
  itemization(
  eit() Borrowed from mksh
   verb(
     ${| code }
   )
   Runs code in the current shell context and then substitutes mytt(${REPLY}).
   The result is not split into words unless the tt(SH_WORD_SPLIT) option
   is set, for example by mytt(${=${| code }}).

  eit() An extension to #1
   verb(
     ${|var| code }
   )
   Runs code in the current shell and then substitutes mytt(${var}).  If
   mytt(${var}) names an array, the result is an array of those elements,
   but no further splitting is done without tt(SH_WORD_SPLIT).

  eit() The traditional ksh form, except that the closing mytt(;)
   may usually be omitted:
   verb(
     ${ code }
   )
   Runs code in the current shell and substitutes its standard output.
   (this is done with a temporary file ala mytt($(<=( code ))) but
   without the fork implied by mytt(=(...))).  The result is not split
   into words without tt(SH_WORD_SPLIT).
  )

  In all three forms mytt(code) behaves myem(similarly) to an anonymous
  function invoked like:
  verb(
    () { local REPLY; code } "$@"
  )
  Thus, mytt($REPLY) is implicitly local and returns to its previous
  value after the substitution ends, all other parameters declared from
  inside the substitution are also local by default, and positional
  parameters mytt($1), mytt($2), etc. are those of the calling context.

  The most significant limitation is that braces (mytt({) and mytt(}))
  within the substitutions must either be in balanced pairs, or must be
  quoted, that is, included in a quoted string or prefixed by backslash.
  These substitutions first become usable after zsh 5.9.

sect(Comparisons of forking and non-forking command substitution)

  mytt(${ command }) and variants may change the caller's options by using
  mytt(setopt) and may modify the caller's local parameters, including the
  positional parameters mytt($1), mytt($2), etc., via both assignments and
  mytt(set -- pos1 pos2 etc).  Nothing that happens within mytt($(command))
  affects the caller.

  mytt($(command)) removes trailing newlines from the output of mytt(command)
  when substituting, whereas mytt(${ command }) and its variants do not.
  The latter is consistent with mytt(${|...}) from mksh but differs from
  bash and ksh, so in emulation modes, newlines are stripped from command
  output (not from tt(REPLY) assignments).

  When not enclosed in double quotes, the expansion of mytt($(command)) is
  split on tt(IFS) into an array of words.  In contrast, and unlike both
  bash and ksh, unquoted non-forking substitutions behave like parameter
  expansions with respect to the tt(SH_WORD_SPLIT) option.

  When mytt(command) is myem(not) a builtin, mytt(${ command }) does fork, and
  typically forks the same number of times as mytt($(command)), because in
  the latter case zsh usually optimizes the final fork into an exec.

  Redirecting input from files has subtle differences:
  itemization(
    it() mytt($(<file)) is optimized to read from mytt(file) without forking,
    	 but per above it removes trailing newlines.
    it() mytt(${<file}) is a substitution error.
    it() mytt(${ <file }) copies mytt(file) using the mytt(NULLCMD) programs,
    	 then reads and substitutes the contents of the copy.  Also, this
	 fails if the tt(CSH_NULLCMD) or tt(SH_NULLCMD) options are in effect,
	 so it does not work in emulation modes.
    it() mytt(${|<file}) copies mytt(file) to the standard output using
    	 tt(NULLCMD) but substitutes nothing because there is no assignment
	 to tt(REPLY).  It also fails in emulation modes.
    )
  mytt(${|IFS= read -rd '' <file}) is therefore the best solution for files
  that do not contain nul bytes, because it copies the file directly into
  the local mytt(REPLY) and then substitutes that.  For very large files,
  refer to mytt(Functions/Misc/zslurp).

chapter(How to get various things to work)

sect(Why does mytt($var) where mytt(var="foo bar") not do what I expect?)
label(31)

  In most Bourne-shell derivatives, multiple-word variables such as
  verb(
    var="foo bar"
  )
  are split into words when passed to a command or used in a mytt(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
  tt(SH_WORD_SPLIT) exists to provide compatibility.

  For example, defining the function args to show the number of its
  arguments:
  verb(
    args() { echo $#; }
  )
  and with our definition of `var',
  verb(
    args $var
  )
  produces the output `1'.  After
  verb(
    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 written
  for other shells (see link(2.8)(28)).  The natural way to produce
  word-splitting behaviour in zsh is via arrays.  For example,
  verb(
    set -A array one two three twenty
  )
  (or
  verb(
    array=(one two three twenty)
  )
  if you prefer), followed by
  verb(
    args $array
  )
  produces the output `4', regardless of the setting of tt(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 word splitting happens regardless of the value of the internal field
  separator, tt($IFS); in other words, with mytt(IFS=:; foo=a:b; args $foo)
  you get the answer 1.

  Other ways of causing word splitting include a judicious use of
  `eval':
  COMMENT(CHAR(39) is a workaround for a bug in some versions of yodl)\
  verb(
    sentence="Longtemps, je me suis couch\\CHAR(39)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 mytt(') in this example,
  must already be quoted), or, less standard but more reliable,
  turning on tt(SH_WORD_SPLIT) for one variable only:
  verb(
    args ${=sentence}
  )
  always returns 8 with the above definition of mytt(args).  (In older
  versions of zsh, tt(${=foo}) toggled tt(SH_WORD_SPLIT); now it forces it on.)

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

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

  There used to be another effect of word splitting which differed between ksh
  and zsh.  In ksh, the builtin commands that declare parameters such
  as tt(typeset) and tt(export) force word-splitting not to take place
  after on an assignment argument:
  verb(
    typeset param=`echo foo bar`
  )
  in ksh will create a parameter with value mytt(foo bar).
  
  zsh used to
  create a parameter tt(param) with value tt(foo) and a parameter tt(bar)
  whose value was empty.  Contrast this with a normal assignment (no
  tt(typeset) or other command in front), which never causes a word split
  unless you have tt(GLOB_ASSIGN) set.
  
  zsh version 4.0.2 and newer creates a single parameter with value
  mytt(foo bar), like ksh does, when the option tt(KSH_TYPESET) is set.
  This option gets set automatically when in ksh compatibility mode.

  zsh 5.1 and newer create a single parameter with value mytt(foo bar) by
  default, in both compatibility and native modes. The older behaviour
  can be obtained with mytt(disable -r typeset).

  If the options mytt(MAGIC_EQUAL_SUBST) and mytt(KSH_TYPESET) are both
  set, arguments that look like assignments will not undergo word
  splitting, whatever the command name.

sect(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: tt(.zshenv), tt(.zprofile), tt(.zshrc)
  and tt(.zlogin).  They are usually in your home directory, but the
  variable tt($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
  tt(/etc/zshenv) by starting zsh with the tt(-f) option --- for this
  reason it is important for administrators to make sure tt(/etc/zshenv)
  is as brief as possible.

  The order in which the four files are searched (none of them
  myem(need) to exist) is the one just given.  However, tt(.zprofile)
  and tt(.zlogin) are only run when the shell is a login shell --- when
  you first login, of course, and whenever you start zsh with the tt(-l)
  option.  The order is the only difference between those; you should
  decide whether you need things set before or after tt(.zshrc).  These
  files are a good place to set environment variables (i.e. mytt(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 tt(xterm) you will need to put those in
  tt(.zshrc), since usually you do not get a login shell here).

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

  The only file you can alter which is started with every zsh (unless
  you use the tt(-f) option) is tt(.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 tt(EXTENDED_GLOB), any changes to set with
  mytt(limit), any more variables you want to make sure are set as for
  example tt($fpath) to find functions.  You almost certainly do not
  want tt(.zshenv) to produce any output.  Some people prefer not to
  use tt(.zshenv) for setting options, as this affects scripts; but
  making zsh scripts portable usually requires special handling anyway.

  Finally, tt(.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 mytt(zsh) or opening a new terminal emulator window.
  This file is the place to change the editing behaviour via options or
  mytt(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 tt(.zshrc) to produce output, either,
  since there are occasions when this can be a problem, such as when
  using mytt(rsh) from another host.  See link(3.21)(321) for what to \
  put in tt(.zshrc)
  to save your history.

sect(What is the difference between `export' and the tt(ALL_EXPORT) option?)

  Normally, you would put a variable into the environment by using
  mytt(export var).  The command mytt(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:
  enumeration(
  myeit() 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.
  myeit() It really is mybf(every) variable which is exported, even loop
     variables in mytt(for) loops.  This is probably a waste.
  myeit() 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 tt(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.

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

  In the first case, you presumably have mytt(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
  mytt(nocorrect) stuck on the front, e.g.
  verb(
    alias mkdir='nocorrect mkdir'
  )

  To turn off globbing, the rationale is identical:
  verb(
    alias mkdir='noglob mkdir'
  )
  You can have both tt(nocorrect) and tt(noglob), if you like, but the
  tt(nocorrect) must come first, since it is needed by the line editor,
  while tt(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.

sect(How do I get the Meta key to work on my xterm?)
label(35)

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

  As stated in the manual, zsh needs to be told about the Meta key by
  using mytt(bindkey -me) or mytt(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; mytt(stty pass8) is the
  usual incantation.  Sample .zshrc entry:
  verb(
    [[ $TERM = "xterm" ]] && stty pass8 && bindkey -me
  )
  or, on SYSVR4-ish systems without pass8,
  verb(
    [[ $TERM = "xterm" ]] && stty -parenb -istrip cs8 && bindkey -me
  )
  (disable parity detection, don't strip high bit, use 8-bit characters).
  Make sure this comes myem(before) any bindkey entries in your .zshrc which
  redefine keys normally defined in the emacs/vi keymap.  You may also
  need to set the tt(eightBitOutput) resource in your tt(~/.Xdefaults)
  file, although this is on by default and it's unlikely anybody will
  have tinkered with it.

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

  If you are using multibyte input directly from the keyboard you
  probably don't want to use this feature since the eighth bit in
  each byte is used to indicate a part of a multibyte character.  See
  link(chapter 5)(c5).

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

  You should use the special function mytt(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 tt(xterm) or some close relative, or a tt(sun-cmd).
  
  verb(
  chpwd() {
    [[ -t 1 ]] || return
    case $TERM in
      sun-cmd+CHAR(41) print -Pn "\e]l%~\e\\"
        ;;
      *xterm*|rxvt|(dt|k|E)term+CHAR(41) print -Pn "\e]2;%~\a"
        ;;
    esac
  }
  )

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

sect(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 tt(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
  tt(setlocale(3)) and tt(zshparam(1)) manual pages: the simplest
  possibility may be to set tt(LC_ALL=en_US).  For older versions of the
  shell, there is no easy way out.

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

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

  verb(
    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 mytt(vi-backward-char) and mytt(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 mytt(<ESC>O) followed by tt(A),
  tt(B), tt(C) or tt(D), as well as the corresponding set beginning
  mytt(<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.
  verb(
    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 tt(.zshrc).  Of course
  you can substitute variant functions for the second argument here too.

  It should be noted that the mytt(O) / mytt([) confusion can occur
  with other keys such as Home and End.  Some systems let you query
  the key sequences sent by these keys from the system's terminal
  database, terminfo.  Unfortunately, the key sequences given there
  typically apply to the mode that is not the one zsh uses by default (it's
  the "application" mode rather than the "raw" mode).  Explaining the use
  of terminfo is outside the scope of this FAQ, but if you wish to use the
  key sequences given there you can tell the line editor to turn on
  "application" mode when it starts and turn it off when it stops:
  verb(
    function zle-line-init () { echoti smkx }
    function zle-line-finish () { echoti rmkx }
    zle -N zle-line-init
    zle -N zle-line-finish
  )
  If you only have the predecessor to terminfo, called termcap (which is
  what we used to get the cursor keys above), replace mytt(echoti smkx)
  with mytt(echotc ks) and replace mytt(echoti rmkx) with mytt(echotc ke).

sect(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
  verb(
    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:  mytt(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 `tt(X)'
  into the environment variable tt(LESS) to stop the sequences being sent.
  Other programs (though not zsh) may also send that sequence.

  If myem(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. tt(^V) is getting interpreted as `literal next
  character' when you don't want it to be), try
  verb(
    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 tt(stty(1)) manual page).

sect(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 mytt($EMACS), which is set to mytt(t) in
  Emacs' shell mode.  Putting
  verb(
    [[ $EMACS = t ]] && unsetopt zle
  )
  in your .zshrc should be sufficient.

  Another method is to put
  verb(
    #!/bin/sh
    TERM=emacs exec zsh
  )
  into a file ~/bin/eshell, then mytt(chmod +x ~/bin/eshell), and
  tell emacs to use that as the shell by adding
  verb(
    (setenv "ESHELL" (expand-file-name "~/bin/eshell"))
  )
  to ~/.emacs.

sect(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):
  enumeration(
  myeit() The file contains just the body of the function, i.e.
     there should be no line at the beginning saying mytt(function foo {)
     or mytt(foo () {), and consequently no matching mytt(}) 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 mytt(xhead () { print -n "\033]2;$*\a"; }),
     the file would just contain mytt(print -n "\033]2;$*\a").  
  myeit() 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 mytt(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 tt(KSH_AUTOLOAD) to allow full ksh
  compatibility, i.e. the function myem(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 mytt(emulate ksh) is in effect, of course.
  
  (A neat trick to autoload all functions in a given directory is to
  include a line like mytt(autoload ~/fns/*(:t)) in .zshrc; the bit in
  parentheses removes the directory part of the filenames, leaving
  just the function names.)

sect(How does base arithmetic work?)

  The ksh syntax is now understood, i.e.
  verb(
    let 'foo = 16#ff'
  )
  or equivalently
  verb(
    (( foo = 16#ff ))
  )
  or even
  verb(
    foo=$((16#ff))
  )
  The original syntax was
  verb(
    (( foo = [16]ff ))
  )
  --- this was based on a misunderstanding of the ksh manual page.  It
  still works but its use is deprecated.  Then
  verb(
    echo $foo
  )
  gives the answer `255'.  It is possible to declare variables explicitly
  to be integers, via
  verb(
    typeset -i foo
  )
  which has a different effect: namely the base used in the first
  assignment (hexadecimal in the example) is subsequently used whenever
  `foo' is displayed (although the internal representation is unchanged).
  To ensure foo is always displayed in decimal, declare it as
  verb(
    typeset -i 10 foo
  )
  which requests base 10 for output.  You can change the output base of an
  existing variable in this fashion.  Using the mytt($(( ... ))) method will
  always display in decimal, except that in 3.1.9 there is a new feature
  for selecting a base for displaying here:
  verb(
    print $(( [#16] 255 ))
  )

sect(How do I get a newline in my prompt?)
label(313)

  You can place a literal newline in quotes, i.e.
  verb(
    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
  mytt(unsetopt cshjunkiequotes) and mytt(setopt cshjunkiequotes), or put it
  in your tt(.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 `tt(\n)' but otherwise acts like single
  quotes: surround the string with tt($'...').  Hence:
  verb(
    PROMPT=$'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 `tt(\n)' into a newline.

sect(Why does mytt(bindkey ^a command-name) or mytt(stty intr ^-) do something funny?)

  You probably have the extendedglob option set in which case tt(^) and tt(#)
  are metacharacters.  tt(^a) matches any file except one called tt(a), so the
  line is interpreted as bindkey followed by a list of files.  Quote the
  tt(^) with a backslash or put quotation marks around tt(^a).
  See link(3.27)(327) if you want to know more about the pattern
  character mytt(^).

sect(Why can't I bind tt(\C-s) and tt(\C-q) any more?)

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

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

sect(How do I execute command mytt(foo) within function mytt(foo)?)

  The command mytt(command foo) does just that.  You don't need this with
  aliases, but you do with functions.  Note that error messages like
  verb(
    zsh: job table full or recursion limit exceeded
  )
  are a good sign that you tried calling `foo' in function `foo' without
  using `command'.  If mytt(foo) is a builtin rather than an external
  command, use mytt(builtin foo) instead.

sect(Why do history substitutions with single bangs do something funny?)

  If you have a command like "tt(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
  tt(!-2:$).  The option tt(CSH_JUNKIE_HISTORY) makes all single bangs refer
  to the last command.

sect(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 mytt(nohup)
  option exists if you don't want them killed.  Note that you can always
  run programs with mytt(nohup) in front of the pipeline whether or not the
  option is set, which will prevent that job from being killed on
  logout.  (mytt(nohup) is actually an external command.)

  The mytt(disown) builtin is very useful in this respect: if zsh informs
  you that you have background jobs when you try to logout, you can
  mytt(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 mytt(&!) instead of just
  mytt(&) at the end, which will automatically disown the job.

sect(How do I list all my history entries?)

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

sect(How does the alternative loop syntax, e.g. mytt(while {...} {...}) \
work?)

  Zsh provides an alternative to the traditional sh-like forms with mytt(do),
  verb(
    while TEST; do COMMANDS; done
  )
  allowing you to have the COMMANDS delimited with some other command
  structure, often mytt({...}).  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:
  verb(
    while (( i++ < 10 )) { echo i is $i; }
  )
  but this does myem(not):
  verb(
    while let "i++ < 10"; { echo i is $i; }   # Wrong!
  )
  The reason is that after mytt(while), any sort of command list is valid.
  This includes the whole list mytt(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 mytt({...}) part
  of the argument to mytt(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 mytt(while) must
  be wrapped up:  any of mytt(((...))), mytt([[...]]), mytt({...}) or
  mytt((...)) 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:
  verb(
    while (( i++ < 10 )); { echo i is $i; }   # Wrong!
  )

  The same is true of the mytt(if) and mytt(until) constructs:
  verb(
    if { true } { echo yes } else { echo no }
  )
  but with mytt(for), which only needs a list of words, you can get
  away with it:
  verb(
    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 mytt(repeat),
  mytt(case) or mytt(select) constructs; in fact, mytt(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.

sect(Why is my history not being saved?)
label(321)

  In zsh, you need to set three variables to make sure your history is
  written out when the shell exits.  For example,
  verb(
    HISTSIZE=200
    HISTFILE=~/.zsh_history
    SAVEHIST=200
  )
  tt($HISTSIZE) tells the shell how many lines to keep internally,
  tt($HISTFILE) tells it where to write the history, and tt($SAVEHIST),
  the easiest one to forget, tells it how many to write out.  The
  simplest possibility is to set it to the same as tt($HISTSIZE) as
  above.  There are also various options affecting history; see the
  manual.

sect(How do I get a variable's value to be evaluated as another variable?)
label(322)

  The problem is that you have a variable tt($E) containing the string
  mytt(EDITOR), and a variable tt($EDITOR) containing the string mytt(emacs),
  or something such.  How do you get from tt($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:
  verb(
    print ${(e)E:+\$$E}
  )
  Ignore the mytt((e)) for now.  The mytt(:+) means: if the variable
  tt($E) is set, substitute the following, i.e. mytt(\$$E).  This is
  expanded to mytt($EDITOR) by the normal rules.  Finally, the mytt((e)) \
  means
  `evaluate the expression you just made'.  This gives mytt(emacs).

  For a standard shell way of doing this, you are stuck with mytt(eval):
  verb(
    eval echo \$$E
  )
  produces the same result.

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

  As a slight aside, sometimes people note that the syntax mytt(${${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,
  mytt(${${file##**/}%.*}) removes everything up to the last slash in
  mytt($file), then everything from the last dot on, inclusive (try
  it, this works).  So in mytt(${${E}}), the internal mytt(${...})
  actually does nothing.

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

  The problem is normally limited to zsh versions prior to 4.3.0 due to the
  advent of the PROMPT_SP option (which is enabled by default, and eliminates
  this problem for most terminals).  An example of the overwriting is:
  verb(
    % echo -n foo
    % 
  )
  This shows a case where the word tt(foo) was output without a newline, and
  then overwritten by the prompt line tt(%).  The reason this happens is that
  the option tt(PROMPT_CR) is enabled by default, and it outputs a carriage
  return before the prompt in order to ensure that the line editor knows what
  column it is in (this is needed to position the right-side prompt correctly
  (mytt($RPROMPT), mytt($RPS1)) and to avoid screen corruption when performing
  line editing).  If you add tt(unsetopt promptcr) to your tt(.zshrc), you
  will see any partial output, but your screen may look weird until you press
  return or refresh the screen.

  A better solution than disabling PROMPT_CR (for most terminals) is adding
  a simpler version of the PROMPT_SP functionality to an older zsh using a
  custom precmd function, like this one:
  verb(
    # Skip defining precmd if the PROMPT_SP option is available.
    if ! eval '[[ -o promptsp ]] 2>/dev/null'; then
      function precmd {
        # Output an inverse char and a bunch spaces.  We include
        # a CR at the end so that any user-input that gets echoed
        # between this output and the prompt doesn't cause a wrap.
        print -nP "%B%S%#%s%b${(l:$((COLUMNS-1)):::):-}\r"
      }
    fi
  )
  That precmd function will only bump the screen down to a new line if there
  was output on the prompt line, otherwise the extra chars get removed by
  the PROMPT_CR action.  Although this typically looks fine, it may result
  in the spaces preceding the prompt being included when you select a line
  of preserved text with the mouse.

  One final alternative is to put a newline in your prompt -- see question
  link(3.13)(313) for that.

sect(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:
  enumeration(
  myeit() 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.
  myeit() 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 `tt({)' on a line
     by itself, then paste the input, then type `tt(})' on a line by
     itself.  The shell will not execute anything until the final brace is
     read; all input is read as continuation lines (this may require the
     fixes referred to above in order to be reliable).

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

sect(How do I get coloured prompts on my colour xterm?)

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

  Versions of the shell starting with the 4.3 series have this
  built in.  Use
  verb(
    PS1='%K{white}%F{red}<red on white>%f%k<default colours>'
  )
  to change the prompt.  Names are only usable for the colours
  black, red, green, yellow, blue, magenta, cyan and white, understood
  by most terminals, but if you happen to know the details of how
  your terminal implements colours you can specify a number, e.g.
  mytt(%20F) to turn the foreground into colour number 20. mytt(echotc
  Co) will often output the number of colours the terminal supports.
  (Careful: mytt(echotc co) is different; it also outputs a number
  but it's the number of columns in the terminal.)  If this is 8
  then probably you have the named colours and nothing more.

  In older versions of the shell you need to find the sequences which
  generate the various colours from the manual for your terminal
  emulator; these are ANSI standard on those I know about which support
  colour.  With a recent (post 3.1.6) distribution of zsh, there is a
  theme system to handle this for you; even if you don't see that, the
  installed function `mytt(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):
  verb(
    PS1=$'%{\e[1;31m%}<the rest of your prompt here>%{\e[0m%}'
  )
  The mytt($') form of quoting turns the `mytt(\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
  verb(
    PS1="$(print '%{\e[1;31m%}<the rest goes here>%{\e[0m%}')"
  )
  The `mytt(%{...%})' 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 `mytt(<ESC>[1;31m)' makes the prompt red, and the
  `mytt(<ESC>[0m)' puts printing back to normal so that the rest of the line
  is unchanged.

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

  This is a slightly unexpected effect of the option tt(MULTIOS), which is
  set by default.  Let's look more closely:
  verb(
    foo 2>&1 >foo.out | bar
  )
  What you're probably expecting is that the command mytt(foo) sends its
  standard output to the pipe and so to the input of the command mytt(bar),
  while it sends its standard error to the file mytt(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:
  verb(
    % { print output; print error >&2 } 2>&1 >foo.out | sed 's/error/erratic/'
    erratic
    output
    % cat foo.out
    output
  )
  and you can see `tt(output)' appears twice.

  It becomes clearer what's going on if we write:
  verb(
    % 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 `tt(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 unset the option tt(MULTIOS), or alternatively write the following:
  verb(
    % { print output; print error >&2 } 2>&1 >&- >foo.out | sed 's/error/erratic/'
    erratic
  )
  By closing stdout with tt(>&-), we're cancelling the previous redirections
  (to the pipe) and start anew with tt(>foo.out) instead of adding it as a
  redirection target to stdout.

sect(What are these `^' and `~' pattern characters, anyway?)
label(327)

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

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

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

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

  It's not obvious what something like mytt([[ $string = ^pat1^pat2 ]])
  means.  You won't often have cause to use it, but the rule is that
  each mytt(^) takes em(everything) that follows as an argument (unless
  it's already inside parentheses --- I'll explain this below).  To see
  this more clearly, put those arguments in parentheses: the pattern is
  equivalent to mytt(^(pat1^(pat2))). where now you can see exactly what
  each mytt(^) takes as its argument.  I'll leave it as an exercise for
  you to work out what this does and doesn't match.
  
  mytt(~) is always used between two patterns --- never right at the
  beginning or right at the end.  Note that the other special meaning of
  mytt(~), at the start of a filename to refer to your home directory or
  to another named directory, doesn't require the option
  tt(EXTENDED_GLOB) to be set.  (At the end of an argument mytt(~) is
  never special at all.  This is useful if you have Emacs backup files.)
  It means `match what's in front of the tilde, but only if it doesn't
  match what's after the tilde'.  So mytt(*.c~f*) matches any file
  ending in tt(.c) except one that begins with tt(f).  You'll see that,
  unlike mytt(^), the parts before and after the mytt(~) both refer
  separately to the entire test string.

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

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

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

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

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

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

sect(How do I edit the input buffer in $EDITOR?)
label(328)

  When typing a long command interactively, it's possible to edit it in $EDITOR
  before execution by using the tt(edit-command-line) ZLE widget.  For example,
  after putting
  verb(
    autoload -U edit-command-line; 
    zle -N edit-command-line; 
    bindkey '^Fc' edit-command-line;
  )
  in your tt(~/.zshrc), typing mytt(^F c) will open the entered-so-far
  command-line for editing.  The command will not be automatically executed;
  quitting the editor will only return to zsh's command-line editing mode.

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

  The issue is that if you run:
  verb(
    which non-existent-command
  )
  the error message goes, unusually, to standard output rather than
  to standard error.  Other shells send this message to standard error,
  as they would if the command was about to be executed but could not be
  found.

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

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

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

  Based on the behaviour of some other shells, you might guess that the
  following expression:
  verb(
    echo *.{tex,aux,pdf}
  )
  would be the way to echo any files ending in mytt(.tex), mytt(.aux) or
  mytt(.pdf) in the current directory.  Depending on your settings for
  matching (see link(2.1)(21), in particular tt(NO_NOMATCH)), you may
  see something else, in particular an error about (say) mytt(*.aux) if
  there were no files ending mytt(.aux).

  The reason for this is that the brace expansion isn't actually
  a form of pattern matching.  Instead, the line above is equivalent to
  verb(
    echo *.tex *.aux *.pdf
  )
  giving you three separate patterns.  With the default mytt(NOMATCH)
  behaviour in effect, any pattern that fails to match is an error.

  However, there em(is) a way of doing exactly what you want, using
  parentheses instead of braces:
  verb(
    echo *.(tex|aux|pdf)
  )
  This is now a pattern matching expression, so is considered as a
  single pattern.  Now any file that exists will suppress the
  mytt(NOMATCH) behaviour, but you'll still get all the files that do
  match.

  This use of parentheses is special to zsh.  Modern Bourne-like shells
  have a syntax like this, too, but with an mytt(@) in front of the
  parentheses: again, see link(2.1)(21), and search for mytt(@_LPAR_).
  This is harder for the user to remember but easier for the shell to
  parse!

chapter(The mysteries of completion)

sect(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 mytt(\C-x g), which lists expansions.)  Expansion is generally
  fairly intuitive and not under user control; for the rest of the
  chapter I will discuss completion only.

  An elegant completion system appeared in version 4, replacing the old
  tt(compctl) command.  This is based on functions called automatically for
  completion in particular contexts (for example, there is a function
  called tt(_cd) to handle completion for the tt(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 `tt(autoload -U
  compinit; compinit)' in your tt(.zshrc) should be enough if the system is
  installed properly.

sect(What sorts of things can be completed?)
label(42)

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

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

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

sect(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 tt(\C-D) to see all the possible completions.
  (That's assuming you're at the end of the line, otherwise tt(\C-D) will
  delete the next character and you have to use tt(ESC-\C-D).)  This can be
  changed by the following options, among others:
  itemization(
   it() with tt(NO_BEEP) set, that annoying beep goes away
   it() with tt(NO_LIST_BEEP), beeping is only turned off for ambiguous
      completions
   it() with tt(AUTO_LIST) set, when the completion is ambiguous you get a
      list without having to type tt(\C-D)
   it() with tt(BASH_AUTO_LIST) set, the list only happens the second
      time you hit tab on an ambiguous completion
   it() with tt(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 tt(BASH_AUTO_LIST), so that where both are
      applicable you need to hit tab three times for a listing.
   it() with tt(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
   it() with tt(AUTO_MENU), you only get the menu behaviour when you hit TAB
      again on the ambiguous completion.
   it() Finally, although it affects all completion lists, including
      those explicitly requested, note also tt(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, tt(AUTO_LIST) and
  tt(AUTO_MENU) together give an intuitive combination.  Note that
  from version 3.1 tt(LIST_AMBIGUOUS) is set by default; if you use
  autolist, you may well want to `unsetopt listambiguous'.

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

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

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

  To complete just what's before the cursor, ignoring anything after, you
  need the function tt(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. mytt(^X TAB) in
  tt(~/.zshrc):
  verb(
    bindkey "^X^I" expand-or-complete-prefix
  )

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

sect(How do I get started with programmable completion?)
label(45)

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

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

  If you're using the completion system the shell will decide what
  to complete when you hit TAB.  That's usually the right thing for
  the context, but sometimes you just want to complete files, like
  TAB used to do in the old days.  You can set up this up as follows:
  verb(
    zle -C complete-file complete-word _generic
    zstyle ':completion:complete-file::::' completer _files
    bindkey '^xF' complete-file
  )
  This turns the key tt(\C-x F) into a command tt(complete-file) which
  goes straight to the completion system's file completion command,
  ignoring the normal context.  Change the binding how you like.

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

  If you simply want to try filename completion as a default when other
  completions fail, add it to the `tt(completer)' style for normal
  completion, for example:
  verb(
    zstyle ':completion:*' completer _complete _ignored _files
  )
  This adds filename completion to the end of the default types of
  completion.  Your actual completer style may include other actions,
  such as expansion or approximate completion.

chapter(Multibyte input and output)
label(c5)

sect(What is multibyte input?)

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

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

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

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

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

sect(How does zsh handle multibyte input and output?)

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

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

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

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

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

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

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

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

  There are basically three components.

  itemization(
   it() The locale.  This describes a whole series of features specific
      to countries or regions of which the character set is one.
      Usually it is controlled by the environment variable tt(LANG)
      (there are others but this is the one to start with).  If you have
      a recent operating system, very likely it is already set
      appropriately.  Otherwise, you need to find a locale whose name
      contains mytt(UTF-8).  This will be a variant on your usual
      locale, which typically indicates the language and country; for
      example, mine is mytt(en_GB.UTF-8).  Luckily, zsh can complete
      locale names, so if you have the new completion system loaded you
      can type mytt(export LANG=) and attempt to complete a suitable
      locale.  It's the locale that tells the shell to expect the right
      form of multibyte input.  (However, there's no guarantee that the
      shell is actually going to get this input: for example, if you
      edit file names that have been created using a different character
      set it won't work properly.)
   it() The terminal emulator.  Those that are supplied with a recent
      desktop environment, such as tt(konsole) and tt(gnome-terminal), are
      likely to have extensive support for localization and may work
      correctly as soon as they know the locale.  You can enable UTF-8
      support for tt(xterm) in its application defaults file.  The
      following are the relevant resources; you don't actually need all of
      them, as described below.  If you use a mytt(~/.Xdefaults) or
      mytt(~/.Xresources) file for setting resources, prefix all the lines
      with mytt(xterm):
      verb(
        *wideChars: true
        *locale: true
        *utf8: 1
        *vt100Graphics: true
      )
      This turns on support for wide characters (this is enabled by the
      tt(utf8) resource, too); enables conversions to UTF-8 from other
      locales (this is the key resource and actually overrides
      mytt(utf8)); turns on UTF-8 mode (this resource is mostly used to
      force use of UTF-8 characters if your locale system isn't up to it);
      and allows certain graphic characters to work even with UTF-8
      enabled.  (Thanks to Phil Pennock for suggestions.)
   it() The font.  If you selected this from a menu in your terminal
      emulator, there's a good chance it already selected the right
      character set to go with it.  If you hand-picked an old fashioned
      X font with a lot of dashes, you need to make sure it ends with
      the right character encoding, mytt(iso10646-1) (and not, for
      example, mytt(iso8859-1)).  Not all characters will be available
      in any font, and some fonts may have a more restricted range of
      Unicode characters than others.
  )

  As mentioned in the previous section, mytt(bindkey -m) now outputs
  a warning message telling you that multibyte input from the terminal
  is likely not to work.  (See link(3.5)(35) if you don't know what
  this feature does.)  If your terminal doesn't have characters
  that need to be input as multibyte, however, you can still use
  the meta bindings and can ignore the warning message.  Use
  mytt(bindkey -m 2>/dev/null) to suppress it.

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

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

  Two functions are provided with zsh that help you input characters.
  As with all editing widgets implemented by functions, you need to
  mark the function for autoload, create the widget, and, if you are
  going to use it frequently, bind it to a key sequence.  The
  following binds tt(insert-composed-char) to F5 on my keyboard:
  verb(
    autoload -Uz insert-composed-char
    zle -N insert-composed-char
    bindkey '\e[15~' insert-composed-char
  )

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

  tt(insert-composed-char) is followed by two characters that
  are a mnemonic for a multibyte character.  For example mytt(a:)
  is a with an Umlaut; mytt(cH) is the symbol for hearts on a playing
  card.  Various accented characters, European and related alphabets,
  and punctuation and mathematical symbols are available.  The
  mnemonics are mostly those given by RFC 1345, see
  url(http://www.faqs.org/rfcs/rfc1345.html)\
(http://www.faqs.org/rfcs/rfc1345.html).

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

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

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

chapter(The future of zsh)

sect(What bugs are currently known and unfixed? (Plus recent \
important changes))
label(61)

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

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

sect(Where do I report bugs, get more info / who's working on zsh?)
label(62)

  The shell is being maintained by various (entirely self-appointed)
  subscribers to the mailing list,
  verb(
    zsh-workers@zsh.org
  )
  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.

  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,
  verb(
    zsh-users@zsh.org
  )
  and one just containing announcements:  about releases, about major
  changes in the shell, or this FAQ, for example,
  verb(
    zsh-announce@zsh.org
  )
  (posting to the last one is currently restricted).

  Finally, there is a private mailing list (the general public cannot subscribe
  to it) for discussing bug reports with security implications, i.e., potential
  vulnerabilities: mytt(zsh-security@zsh.org).  If you find a security problem
  in zsh itself, please mail this address.

  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
  verb(
    zsh-workers-subscribe@zsh.org
  )
  (the actual content is unimportant).  Replace tt(subscribe) with
  tt(unsubscribe) to unsubscribe.  The mailing software (tt(Sympa)) has
  various bells and whistles: you can retrieve archived messages.
  Mail email(sympa@zsh.org?subject=help) for detailed information.
  Administrative matters are best sent to
  email(zsh-workers-owner@zsh.org).

  Note that this location changed in August 2020, and the
  instructions to go with it are slightly different.

  An archive of mailings for the last few years can be found at
    url(http://www.zsh.org/mla/)(http://www.zsh.org/mla/)
  at the main zsh archive site.

sect(What's on the wish-list?)

  The code 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.

  Some future possibilities which have been suggested:
  itemization(
  it() The shell, in particular the line editor, should support Unicode
     characters.  Initial support for this appeared in version 4.3;
     it is reasonably complete in the line editor but patchy elsewhere
     (note this may require the configuration option --enable-multibyte).
  it() The parameter code could do with tidying up.
  it() Configuration files to enable zsh startup files to be created
     with the Dotfile Generator.
  it() Further improvements in integrating the line editor with shell
     functions.
  )

sect(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 mytt(%W) and mytt(%D),
  and also by the command `tt(print -P)'.  Earlier versions of zsh may
  show problems here.

sect(When reporting a bug, how do I reduce my mytt(.zshrc) into a minimal reproduction recipe?)

  When reporting a bug, the gold standard is to include with the bug
  a myem(minimal reproduction recipe), with which anyone who reads the bug
  report can url(reproduce the bug for themselves)
  (https://www.chiark.greenend.org.uk/~sgtatham/bugs.html#showmehow)
  at will.

  When you run into a bug in the shell, particularly during interactive
  use, a reproduction recipe would ideally start by running tt(zsh -f)
  and then, within that instance of the shell, run a minimal short
  sequence of commands that reproduces the bug.  A good way to devise
  such recipes is the following:
COMMENT(For reference, here's Vim's write-up of a similar process:
https://github.com/chrisbra/vim_faq/blob/de424bd8e08bcf0e6b1e0563ee49514dfed926ae/vim_faq.txt#L1153-L1228)\

  enumeration(
  myeit() First, ensure the bug is reproducible.  To do this, start
  a new instance of the shell emdash() for example, open a new tab in
  your terminal emulator emdash() and reproduce the bug there.

  myeit() Start a new instance of the shell by running the
  command mytt(zsh -f) from your regular shell prompt, and reproduce the
  bug there.  (The mytt(-f) flag inhibits mytt(.zshenv),
  mytt(/etc/zprofile), mytt(.zprofile), mytt(/etc/zshrc), and
  mytt(.zshrc) from being sourced.)

  If you succeeded in reproducing the bug in mytt(zsh -f), copy the
  commands you used and their outputs (from the mytt(zsh -f) invocation
  to the point the bug occurred) and include them in your bug report.
  Skip the remaining steps of this procedure.

  If, however, the bug happens in your regular shell but not in mytt(zsh
  -f), read the next steps.

  myeit() Make a backup of your tt(.zshrc) file.

  myeit() Delete your tt(.zshrc) file, start a new instance of zsh, and confirm
  that the problem does em(not) reproduce there.  (If the problem
  does reproduce there, it's caused by something in mytt(.zshenv),
  mytt(.zprofile), mytt(/etc/zprofile), or mytt(/etc/zshrc), so apply
  this procedure from the top to those files rather than to your
  mytt(.zshrc).)
  COMMENT(Note that mytt(/etc/zshenv) is not mentioned, since by this
  point we have established the bug does not occur under mytt(zsh -f),
  which sources mytt(/etc/zshenv).)
  COMMENT(mytt(.zlogout) and mytt(/etc/zlogout) aren't mentioned because
  they're unlikely to be relevant to most readers.)

  myeit() At this point, you know that the problem is caused by
  something in your mytt(.zshrc) file, but not what line exactly.
  To find the responsible line, we will use
  a url(variation)(https://en.wikipedia.org/wiki/Delta_debugging)
  of the url(binary search)(https://en.wikipedia.org/wiki/Binary_search)
  algorithm, as follows:

  Suppose your mytt(.zshrc) file has 200 lines.  To start, copy
  the em(first) half of your mytt(.zshrc) emdash() that is, lines
  1 through 100 emdash() from the backup copy to your live mytt(.zshrc)
  file, and check whether the bug reproduces then.  Now, empty the live
  mytt(.zshrc) file again, and copy the em(second) half of your
  mytt(.zshrc) file from the backup to the live mytt(.zshrc) file
  emdash() the live file should now contain lines 101 through 200, only
  emdash() and see whether the problem reproduces.

  Normally, the bug will reproduce em(either) with lines 1 through 100
  em(or) with lines 101 through 200, but not in both cases.  To isolate
  the specific line that causes the bug, repeat the above process on the
  relevant half of the file: for example, if you've determined that the
  bug reproduces when only lines 101 through 200 are installed, check
  whether the bug reproduces (a) when only lines 101 through 150 are
  installed, and (b) when only lines 151 through 200 are installed.
  Repeat the process until the resulting mytt(.zshrc) is minimal.

  It is not important to break the file into two halves exactly.
  Breaking the file into two parts sized one-third and two-thirds, for
  example, will work equally well.  You can even try restoring one line
  at a time, but this is impractical for all but the shortest
  mytt(.zshrc) files.

  myeit() Include the minimal set of lines you devised in the previous
  step, along with the commands you used and their outputs, in your bug
  report.

  myeit() Restore your mytt(.zshrc) from backup.
  )

  Bug reports should be emailed to the mytt(zsh-workers@zsh.org) public
  mailing list; see link(6.2)(62) for details.

nsect(Acknowledgments:)

Thanks to zsh-workers, 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 lists have been managed or hosted by Peter Gray,
Rick Ohnemus, Richard Coleman, Karsten Thygesen, Geoff Wing, Phil
Pennock, Daniel Shahaf, and Oliver Kiddle, 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).

nsect(Copyright Information:)

This document is copyright (C) P.W. Stephenson, 1995, 1996, 1997,
1998, 1999, 2000, 2012, 2020, 2023. 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, this document changes occasionally and it may be more useful
to provide a pointer to it rather than the entire text.  A suitable
pointer is "information on the Z-shell can be obtained on the World
Wide Web at URL https://zsh.sourceforge.io/".
