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Newsgroups: comp.unix.shell,comp.answers,news.answers Path: informatik.tu-muenchen.de!fu-berlin.de!news.mathworks.com!howland.erols.net!nntp.primenet.com!dispatch.news.demon.net!demon!usenet2.news.uk.psi.net!uknet!usenet1.news.uk.psi.net!uknet!uknet!yama.mcc.ac.uk!liv!amtp!pws From: pws@amtp.liv.ac.uk (Peter Stephenson) Subject: Z-shell Frequently-Asked Questions Message-ID: <PWS.96Oct24101833@suna.amtp.liv.ac.uk> Followup-To: comp.unix.shell Summary: Q's and A's about zsh, a powerful (and free) UNIX shell Sender: news@liverpool.ac.uk (News System) Nntp-Posting-Host: suna.amtp.liv.ac.uk Reply-To: Peter Stephenson <pws@amtp.liv.ac.uk> Organization: DAMTP, University of Liverpool Date: Thu, 24 Oct 1996 09:18:32 GMT Approved: news-answers-request@MIT.Edu Expires: Fri, 24 Nov 1995 00:00:00 GMT Lines: 1260 Xref: informatik.tu-muenchen.de comp.unix.shell:43908 comp.answers:21869 news.answers:84929 Archive-Name: unix-faq/shell/zsh Last-Modified: 1996/10/24 Submitted-By: pws@amtp.liv.ac.uk (Peter Stephenson) Version: $Id: zsh.FAQ,v 2.20 1996/10/24 09:15:18 pws Exp $ Frequency: Monthly Copyright: (C) P.W. Stephenson, 1995, 1996 (see end of document) Changes since last issue: - in Z1: removed =(...) bug again mention pushd change 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. In fact, zsh is currently the most powerful freely available shell. If you have never heard of `sh', `csh' or `ksh', then you are probably better off to start by reading a general introduction to UNIX rather than this document. If you just want to know how to get your hands on the latest version, skip to question A5); if you want to know what to do with insoluble problems, go to Z2). Notation: Quotes `like this' are ordinary textual quotation marks. Other uses of quotation marks are input to the shell. Contents: Section A: Introducing zsh and how to install it A0) Sources of information A1) What is it? A2) What is it good at? A3) On what machines will it run? (Plus important compilation notes) A4) What's the latest version? A5) Where do I get it? A6) I don't have root access: how do I make zsh my login shell? Section B: How does zsh differ from...? B1) sh and ksh? B2) csh? B3) Why do my csh aliases not work? (Plus other alias pitfalls.) B4) tcsh? B5) bash? B6) Shouldn't zsh be more/less like ksh/(t)csh? Section C: How to get various things to work C1) How do I turn off spelling correction/globbing for an individual command? C2) How do I get the meta key to work on my xterm? C3) Why does my terminal act funny in some way? C4) Why does `$var' where var="foo bar" not do what I expect? C5) Why do my autoloaded functions not autoload [the first time]? C6) How does base arithmetic work? C7) How do I get a newline in my prompt? C8) Why does `bindkey ^a command-name' or 'stty intr ^-' do something funny? C9) Why can't I bind \C-s and \C-q any more? C10) How do I execute command `foo' within function `foo'? C11) Why do history substitutions with single bangs do something funny? C12) Why does zsh kill off all my background jobs when I logout? C13) How do I list all my history entries? Section D: The mysteries of completion D1) What is completion? D2) What sorts of things can be completed? D3) How does zsh deal with ambiguous completions? D4) How do I get started with programmable completion? D5) And if programmable completion isn't good enough? Section Z: The future of zsh Z1) What bugs are currently known and unfixed? (Plus recent important changes) Z2) Where do I report bugs, get more info / who's working on zsh? Z3) What's on the wish-list? Acknowledgments Copyright --- End of Contents --- Section A: Introducing zsh and how to install it A0) Sources of information Information on zsh is now available via the World Wide Web. The URL is "http://www.mal.com/zsh/". The server provides this FAQ and much else (thanks to Mark Borges for this). The FAQ is at "http://www.mal.com/zsh/FAQ/". Another useful source of information is the collection of FAQ articles posted frequently to the Usenet news groups comp.unix.questions, comp.unix.shells and comp.answers with answers to general questions about UNIX. The fifth of the seven articles deals with shells, including zsh, with a brief description of differences. (This article also talks about shell startup files which would otherwise rate a mention here.) There is also a separate FAQ on shell differences and how to change your shell. Usenet FAQs are available via FTP from rtfm.mit.edu and mirrors and also on the World Wide Web; see USA http://www.cis.ohio-state.edu/hypertext/faq/usenet/top.html UK http://www.lib.ox.ac.uk/internet/news/faq/comp.unix.shell.html Netherlands http://www.cs.ruu.nl/wais/html/na-dir/unix-faq/shell/.html The latest version of this FAQ is also available directly from any of the zsh archive sites listed in question A5). (As a method of reading this in Emacs, you can type \M-2 \C-x $ to make all the indented text vanish, then \M-0 \C-x $ when you are on the title you want.) For any more eclectic information, you should contact the mailing list: see question Z2). A1) What is it? Zsh is a UNIX command interpreter (shell) which of the standard shells most resembles the Korn shell (ksh); it's compatibility with the 1988 Korn shell has been gradually increasing. It includes enhancements of many types, notably in the command-line editor, options for customising its behaviour, filename globbing, features to make C-shell (csh) users feel more at home and extra features drawn from tcsh (another `custom' shell). It was written by Paul Falstad when a student at Princeton; however, Paul doesn't maintain it any more and enquiries should be sent to the mailing list (see question Z2). 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. A2) 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 feature in any other freely-available shell which zsh does not also have (except smallness). Command line editing: programmable completion: incorporates the ability to use the full power of zsh globbing (compctl -g), multi-line commands editable as a single buffer (even files!), variable editing (vared), command buffer stack, print text straight into the buffer for immediate editing (print -z), execution of unbound commands, menu completion, variable, editing function and option name completion, inline expansion of variables, history commands. Globbing --- extremely powerful, including: recursive globbing (cf. find), file attribute qualifiers (size, type, etc. also cf. find), full alternation and negation of patterns. Handling of multiple redirections (simpler than tee). Large number of options for tailoring. Path expansion (=foo -> /usr/bin/foo). Adaptable messages for spelling, watch, time as well as prompt (including conditional expressions). Named directories. Comprehensive integer arithmetic. Manipulation of arrays (including reverse subscripting). Spelling correction. A3) On what machines will it run? From version 3.0, zsh uses GNU autoconf as the installation mechanism. This considerably increases flexibility over the old `buildzsh' mechanism. Consequently, zsh should compile and run on any modern version of UNIX, and a great many not-so-modern versions too. The file Etc/MACHINES in the distribution has more details. If you need to change something to support a new machine, it would be appreciated if you could add any necessary preprocessor code and alter configure.in and config.h.in to configure zsh automatically, then send the required context diffs to the list (see question Z2). Changes based on version 2.5 are very unlikely to be useful. To get it to work, retrieve the source distribution (see question A5), un-gzip it, un-tar it and read the INSTALL file in the top directory. Also read the Etc/MACHINES file for up-to-date information on compilation on certain architectures. *Note for users of nawk* (The following information comes from Zoltan Hidvegi): On some systems nawk is broken and produces an incorrect signames.h file. This make the signals code unusable. This often happens on Ultrix, HP-UX, IRIX (?). Install gawk if you experience such problems. A4) What's the latest version? Zsh 3.0.0 has now been relased; 3.0.1 is under test. The new major number 3.0 largely reflects the considerable internal changes in zsh to make it more reliable, consistent and (where possible) compatible. Those planning on upgrading their zsh installation should take a look at the list of incompatibilities at the end of Z1). This is longer than usual due to enhanced sh, ksh and POSIX compatibility. Development of zsh is usually patch by patch, with each intermediate version publicly available. Note that this `open' development system does mean bugs are sometimes introduced into the most recent archived version. These are usually fixed quickly. Note also that as the shell changes, it may become incompatible with older versions; see the end of question Z1 for a partial list. Changes of this kind are almost always forced by an awkward or unnecessary feature in the original design (as perceived by current users), or to enhance compatibility with other Bourne shell derivatives, or (most recently) to provide POSIX compliancy. A5) Where do I get it? The archive is now run by Zoltan Hidvegi <hzoli@cs.elte.hu>. The following are known mirrors (kept frequently up to date); the first is the official archive site. All are available by anonymous FTP. Hungary ftp://ftp.cs.elte.hu/pub/zsh/ Australia ftp://ftp.ips.gov.au/mirror/zsh/ France ftp://ftp.cenatls.cena.dgac.fr/pub/shells/zsh/ Germany ftp://ftp.fu-berlin.de/pub/unix/shells/zsh/ ftp://ftp.uni-trier.de/pub/unix/shell/zsh/ ftp://ftp.prz.tu-berlin.de/pub/unix/shells/zsh Japan ftp://ftp.tohoku.ac.jp/mirror/zsh/ ftp://ftp.iij.ad.jp/pub/misc/zsh/ Norway ftp://ftp.uit.no/pub/unix/shells/zsh/ Sweden ftp://ftp.lysator.liu.se/pub/unix/zsh/ UK ftp://ftp.net.lut.ac.uk/zsh/ (also by FSP at port 21) USA ftp://ftp.math.gatech.edu/pub/zsh/ ftp://uiarchive.cso.uiuc.edu/pub/packages/shells/zsh/ ftp://ftp.sterling.com/zsh/ ftp://ftp.rge.com/pub/shells/zsh/ (If you don't understand URL's, the first thing after the ftp:// is the hostname and the remainder after the / is the directory. You can supply these directly to a Web browser. If you're reading this with a recent version of Netscape Navigator, you may just have to click on them.) The latest full release is in zsh.tar.gz in these directories. Note that this is in gzip format: you will need GNU gzip from your nearest GNU archive to unpack it. The up-to-the-minute development version is in zsh-beta.tar.gz. There is also a version under RCS control which may be more suitable for source hackers. A6) I don't have root access: how do I make zsh my login shell? Unfortunately, on many machines you can't use `chsh' to change your shell unless the name of the shell is contained in /etc/shells, so if you have your own copy of zsh you need some sleight-of-hand to use it when you log on. (Simply typing `zsh' is not really a solution since you still have your original login shell waiting for when you exit.) The basic idea is to use `exec <zsh-path>' to replace the current shell with zsh. Often you can do this in a login file such as .profile (if your shell is sh or ksh) or .login (if it's csh). Make sure you have some way of altering the file (e.g. via FTP) before you try this as `exec' is often rather unforgiving. If you have zsh in a subdirectory `bin' of your home directory, put this in .profile: [ -f $HOME/bin/zsh ] && exec $HOME/bin/zsh -l or if your login shell is csh or tcsh, put this in .login: if ( -f ~/bin/zsh ) exec ~/bin/zsh -l (in each case the -l tells zsh it is a login shell). If you want to check this works before committing yourself to it, you can make the login shell ask whether to exec zsh. The following work for Bourne-like shells: [ -f $HOME/bin/zsh ] && { echo "Type Y to run zsh: \c" read line [ "$line" = Y ] && exec $HOME/bin/zsh -l } and for C-shell-like shells: if ( -f ~/bin/zsh ) then echo -n "Type Y to run zsh: " if ( "$<" == Y ) exec ~/bin/zsh -l endif It's not a good idea to put this (even without the -l) into .cshrc, at least without some tests on what the csh is supposed to be doing, as that will cause _every_ instance of csh to turn into a zsh and will cause csh scripts (yes, unfortunately some people write these) which do not call `csh -f' to fail. If you want to tell xterm to run zsh, change the SHELL environment variable to the full path of zsh at the same time as you exec zsh (in fact, this is sensible for consistency even if you aren't using xterm). If you have to exec zsh from your .cshrc, a minimum safety check is `if ($?prompt) exec zsh'. If you like your login shell to appear in the process list as '-zsh', you can link zsh to -zsh (e.g. by `ln -s ~/bin/zsh ~/bin/-zsh') and change the exec to `exec -zsh'. (Make sure -zsh is in your path.) This has the same effect as the `-l' option. Footnote: if you DO have root access, make sure zsh goes in /etc/shells on all appropriate machines, including NIS clients, or you may have problems with FTP to that machine. Section B: 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. B1) Differences from sh and ksh Most features of ksh (and hence also of sh) are implemented in zsh; problems can arise because the implementation is slightly different. Note also that not all ksh's are the same either. I have based this on the 11/16/88f version of ksh; differences with ksh93 will be more substantial. As a summary of the status: i) 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; ii) invoking zsh as sh or ksh (or if either is a symbolic link to zsh) sets appropriate options and improves compatibility (from within zsh itself, calling `ARGV0=sh zsh' will also work); iii) 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; iv) the degree of compatibility with ksh is also high, but a few things are missing: for example the more sophisticated pattern-matching expressions are different --- see the detailed list below; v) also from 3.0, the command `emulate' is available: `emulate ksh' and `emulate sh' set various options as well as changing the effect of single-letter option flags as if the shell had been invoked with the appropriate name. Including the commands `emulate sh; setopt localoptions' in a shell function will turn on sh emulation for that function only. The classic difference is word splitting, discussed in C4); this catches out very many beginning zsh users. As explained there, this is actually a bug in every other shell. The answer is to set SH_WORD_SPLIT for backward compatibility. The next most classic difference is that unmatched glob patterns cause the command to abort; set NO_NOMATCH for those. Here is a list of various options which will increase ksh compatibility, though maybe decrease zsh's abilities: see the manual entries for GLOB_SUBST, IGNORE_BRACES (though brace expansion occurs in some versions of ksh), KSH_ARRAYS, KSH_OPTION_PRINT, LOCAL_OPTIONS, NO_BAD_PATTERN, NO_BANG_HIST, NO_EQUALS, NO_HUP, NO_NOMATCH, NO_RCS, NO_SHORT_LOOPS, PROMPT_SUBST, RM_STAR_SILENT, POSIX_BUILTINS, SH_FILE_EXPANSION, SH_GLOB, SH_OPTION_LETTERS, SH_WORD_SPLIT (see question C4) and SINGLE_LINE_ZLE. Note that you can also disable any built-in commands which get in your way. If invoked as `ksh', the shell will try and set suitable options. Here are some differences from ksh which might prove significant for ksh programmers, some of which may be interpreted as bugs; there must be more. Note that this list is deliberately rather full and that most of the items are fairly minor. Those marked `*' perform in a ksh-like manner if the shell is invoked with the name `ksh', or if `emulate ksh' is in effect. Capitalised words with underlines refer to shell options. Syntax: * Shell word splitting: see question C4). * Arrays are (by default) more csh-like than ksh-like: subscripts start at 1, not 0; array[0] refers to array[1]; `$array' refers to the whole array, not $array[0]; braces are unnecessary: $a[1] == ${a[1]}, etc. The KSH_ARRAYS option is now available. Coprocesses are established by `coproc'; `|&' behaves like csh. Command line substitutions, globbing etc.: * Failure to match a globbing pattern causes an error (use NO_NOMATCH). * The results of parameter substitutions are treated as plain text: `foo="*"; print $foo' prints all files in ksh but * in zsh. (GLOB_SUBST has been added to fix this.) The backslash in $(echo '\$x') is treated differently: in ksh, it is not stripped, in zsh it is. (The `...` form gives the same in both shells.) * $PSn do not do parameter substitution by default (use PROMPT_SUBST). Globbing does not allow ksh-style `pattern-lists'. Equivalents: ------------------------------------------------------------------- ksh zsh Meaning ----- ----- --------- !(foo) ^foo Anything but foo. or foo1~foo2 Anything matching foo1 but foo2[1]. @(foo1|foo2|...) (foo1|foo2|...) One of foo1 or foo2 or ... ?(foo) (foo|) Zero or one occurrences of foo. *(foo) (foo)# Zero or more occurrences of foo. +(foo) (foo)## One or more occurrences of foo. ------------------------------------------------------------------- The `^', `~' and `#' (but not `|')forms require EXTENDED_GLOB. [1] Note that ~ is the only globbing operator to have a lower precedence than `/'. For example, `**/foo~*bar*' matches any file in a subdirectory called `foo', except where `bar' occurred somewhere in the path (e.g. `users/barstaff/foo' will be excluded by the ~ operator). As the `**' operator cannot be grouped (inside parentheses it is treated as *), this is the way to exclude some subdirectories from matching a `**'. Unquoted assignments do file expansion after `:'s (intended for PATHs). `integer' does not allow -i. Command execution: * There is no $ENV variable (use /etc/zshrc, ~/.zshrc; note also $ZDOTDIR). $PATH is not searched for commands specified at invocation without -c. Aliases and functions: The order in which aliases and functions are defined is significant (function definitions with () expand aliases -- see question B3). Aliases and functions cannot be exported. There are no tracked aliases: command hashing replaces these. The use of aliases for key bindings is replaced by `bindkey'. * Options are not local to functions (use LOCAL_OPTIONS; note this may always be unset locally to propagate options settings from a function to the calling level). Traps and signals: Traps are not local to functions. TRAPERR has become TRAPZERR (this was forced by UNICOS which has SIGERR). Editing: The options emacs, gmacs, trackall, viraw are not supported. Use bindkey to change the editing behaviour: `set -o {emacs,vi}' become `bindkey -{e,v}'; for gmacs, go to emacs mode and use `bindkey \^t gosmacs-transpose-characters'. `Trackall' is replaced by `hashcmds'. The `keyword' option does not exist and -k is instead interactivecomments. (`keyword' will not be in the next ksh release either.) Management of histories in multiple shells is different: the history list is not saved and restored after each command. \ does not escape editing chars (use ^V). Not all ksh bindings are set (e.g. `<ESC>#'; try <ESC>q). * # in an interactive shell is not treated as a comment by default. Built-in commands: Some built-ins (r, autoload, history, integer ...) were aliases in ksh. There is no built-in command newgrp: use e.g. `alias newgrp="exec newgrp"' `jobs' has no `-n' flag. `read' has no `-s' flag. In `let "i = foo"', foo is evaluated as a number, not an expression (although in `let "i = $foo"' it is treated as an expression). Other idiosyncrasies: `select' always redisplays the list of selections on each loop. B2) 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 scripts/c2z) to help convert .cshrc and .login files; see also the next question concerning aliases, particularly those with arguments. Csh-compatibility additions include: Logout, rehash, source, (un)limit built-in commands. *rc file for interactive shells. Directory stacks. Cshjunkie*, ignoreeof options. The CSH_NULL_GLOB option. >&, |& etc. redirection. (Note that `>file 2>&1' is the standard Bourne shell command for csh's `>&file'.) foreach ... loops; alternative syntax for other loops. Alternative syntax `if ( ... ) ...', though this still doesn't work like csh: it expects a command in the parentheses. Also `for', `which'). $PROMPT as well as $PS1, $status as well as $?, $#argv as well as $#, .... Escape sequences via % for prompts. Special array variables $PATH etc. are colon-separated, $path are arrays. !-type history (which may be turned off via `setopt nobanghist'). Arrays have csh-like features (see under B1)). B3) Why do my csh aliases not work? (Plus other alias pitfalls.) First of all, check you are using the syntax alias newcmd='list of commands' and not alias newcmd 'list of commands' which won't work. (It tells you if `newcmd' and `list of commands' are already defined as aliases.) Otherwise, your aliases probably contain references to the command line of the form `\!*', etc. Zsh does not handle this behaviour as it has shell functions which provide a way of solving this problem more consistent with other forms of argument handling. For example, the csh alias alias cd 'cd \!*; echo $cwd' can be replaced by the zsh function, cd() { builtin cd $*; echo $PWD; } (the `builtin' tells zsh to use its own `cd', avoiding an infinite loop) or, perhaps better, cd() { builtin cd $*; print -D $PWD; } (which converts your home directory to a ~). In fact, this problem is better solved by defining the special function chpwd() (see the manual). Note also that the `;' at the end of the function is optional in zsh, but not in ksh or sh (for sh's where it exists). Here is Bart Schaefer's guide to converting csh aliases for zsh. 1. If the csh alias references "parameters" (\!:1 \!* etc.), then in zsh you need a function (referencing $1 $* etc.). Otherwise, you can use a zsh alias. 2. If you use a zsh function, you need to refer _at_least_ to $* in the body (inside the { }). Parameters don't magically appear inside the { } the way they get appended to an alias. 3. If the csh alias references its own name (alias rm "rm -i"), then in a zsh function you need the "command" keyword (function rm() { command rm -i $* }), but in a zsh alias you don't (alias rm="rm -i"). 4. If you have aliases that refer to each other (alias ls "ls -C"; alias lf "ls -F" ==> lf == ls -C -F) then you must either: a. convert all of them to zsh functions; or b. after converting, be sure your .zshrc defines all of your aliases before it defines any of your functions. Those first four are all you really need, but here are four more for heavy csh alias junkies: 5. Mapping from csh alias "parameter referencing" into zsh function (assuming shwordsplit and ksharrays are NOT set in zsh): csh zsh ===== ========== \!* $* (or $argv) \!^ $1 (or $argv[1]) \!:1 $1 \!:2 $2 (or $argv[2], etc.) \!$ $*[$#] (or $argv[$#], or $*[-1]) \!:1-4 $*[1,4] \!:1- $*[1,$#-1] (or $*[1,-2]) \!^- $*[1,$#-1] \!*:q "$@" ($*:q doesn't work (yet)) \!*:x $=* ($*:x doesn't work (yet)) 6. Remember that it is NOT a syntax error in a zsh function to refer to a position ($1, $2, etc.) greater than the number of parameters. (E.g., in a csh alias, a reference to \!:5 will cause an error if 4 or fewer arguments are given; in a zsh function, $5 is the empty string if there are 4 or fewer parameters.) 7. To begin a zsh alias with a - (dash, hyphen) character, use "alias --": csh zsh =============== ================== alias - "fg %-" alias -- -="fg %-" 8. Stay away from "alias -g" in zsh until you REALLY know what you're doing. There is one other serious problem with aliases: consider alias l='/bin/ls -F' l() { /bin/ls -la $* | more } `l' in the function definition is in command position and is expanded as an alias, defining `/bin/ls' and `-F' as functions which call `/bin/ls', which gets a bit recursive. This can be avoided if you use `function' to define a function, which doesn't expand aliases. It is possible to argue for extra warnings somewhere in this mess. Luckily, it is not possible to define `function' as an alias. B4) Similarities with tcsh: (The sections on csh apply too, of course.) Certain features have been borrowed from tcsh, including $watch, run-help, $savehist, $histlit, periodic commands etc., extended prompts, sched and which built-ins. Programmable completion was inspired by, but is entirely different to, tcsh's `complete'. (There is a perl script called lete2ctl in the Misc directory of the source distribution to convert `complete' to `compctl' statements.) This list is not definitive: some features have gone in the other direction. If you're missing the editor function run-fg-editor, try something with bindkey -s (which binds a string to a keystroke), e.g. bindkey -s '^z' '\eqfg %$EDITOR:t\n' which pushes the current line onto the stack and tries to bring a job with the basename of your editor into the foreground. Bindkey -s allows limitless possibilities along these lines. B5) Similarities with bash Zsh has almost all the features that bash has (and much more); in addition it is about twice as fast, though this is less impressive than it sounds. With the new malloc by Sven Wischnowsky (only used if you used `configure --enable-zsh-mem' when configuring), zsh uses about the same amount of heap memory as bash, which was previously the biggest gripe. The only feature I am aware of that zsh doesn't have is setting a numerical value for ignoreeof --- it's always 10 --- but of course I don't use bash :-). On the other hand, zsh is not strictly POSIX compliant --- though the latest beta version is and production version 3 will be very much more so than the last production version, with the appropriate options set or when invoked as sh or ksh --- and will not use GNU readline (zle is more powerful). In fact, bash is intended more as an enhanced sh than a ksh work-alike; it doesn't handle [[ ... ]], or (yet) arrays, for example. Of course, they're working on bash, too. Some zsh-like features are suggested for future versions. B6) Shouldn't zsh be more/less like ksh/(t)csh? People often ask why zsh has all these `unnecessary' csh-like features, or alternatively why zsh doesn't understand more csh syntax. This is far from a definitive answer and the debate will no doubt continue. Paul's object in writing zsh was to produce a ksh-like shell which would have features familiar to csh users. For a long time, csh was the preferred interactive shell and there is a strong resistance to changing to something unfamiliar, hence the additional syntax and CSH_JUNKIE options. This argument still holds. On the other hand, the arguments for having what is close to a plug-in replacement for ksh are, if anything, even more powerful: the deficiencies of csh as a programming language are well known (look in any Usenet FAQ archive, e.g. http://www.cis.ohio-state.edu/hypertext/faq/usenet/unix-faq/shell/\ csh-whynot/faq.html if you are in any doubt) and zsh is able to run many standard scripts such as /etc/rc. Of course, this makes zsh rather large and feature-ridden so that it seems to appeal mainly to hackers --- but note it is only slightly larger than bash and tcsh, and uses much less memory and CPU time than tcsh. The only answer, perhaps not entirely satisfactory, is that you have to ignore the bits you don't want. Section C: How to get various things to work C1) How do I turn off spelling correction/globbing for an individual command? In the first case, you presumably have `setopt correctall' in an initialisation file, so that zsh checks the spelling of each word in the command line. You probably do not want this behaviour for commands which do not operate on existing files. The answer is to alias the offending command to itself with `nocorrect' stuck on the front, e.g. alias mkdir='nocorrect mkdir' To turn off globbing, the rationale is identical: alias mkdir='noglob mkdir' (you can have both nocorrect and nglob, if you like). C2) How do I get the meta key to work on my xterm? As stated in the manual, zsh needs to be told about the meta key by using `bindkey -me' or `bindkey -mv' in your .zshrc or on the command line. You probably also need to tell the terminal driver to allow the `meta' bit of the character through; `stty pass8' is the usual incantation. Sample .zshrc entry: [[ $TERM = "xterm" ]] && stty pass8 && bindkey -me or, on SYSVR4-ish systems without pass8, [[ $TERM = "xterm" ]] && stty -parenb -istrip cs8 && bindkey -me (disable parity detection, don't strip high bit, use 8-bit characters). Make sure this comes *before* any bindkey entries in your .zshrc which redefine keys normally defined in the emacs/vi keymap. C3) Why does my terminal act funny in some way? If you are using an OpenWindows cmdtool as your terminal, any escape sequences (such as those produced by cursor keys) will be swallowed up and never reach zsh. Either use shelltool or avoid commands with escape sequences. You can also disable scrolling from the cmdtool pane menu (which effectively turns it into a shelltool). If you still want scrolling, try using an xterm with the scrollbar activated. If that's not the problem, and you are using stty to change some tty settings, make sure you haven't asked zsh to freeze the tty settings: type ttyctl -u before any stty commands you use. On the other hand, if you aren't using stty and have problems you may need the opposite: `ttyctl -f' freezes the terminal to protect it from hiccups introduced by other programmes (kermit has been known to do this). If _that's_ not the problem, and you are having difficulties with external commands (not part of zsh), and you think some terminal setting is wrong (e.g. ^V is getting interpreted as `literal next character' when you don't want it to be), try ttyctl -u STTY='lnext "^-"' commandname (in this example), or just export STTY for all commands to see. Note that zsh doesn't reset the terminal completely afterwards: just the modes it uses itself and a number of special processing characters (see the stty(1) manual page). At some point there may be an overhaul which allows the terminal modes used by the shell to be modified separately from those seen by external programmes. This is partially implemented already: from 2.5, the shell is less susceptible to mode changes inherited from programmes than it used to be. C4) Why does `$var' where var="foo bar" not do what I expect? In most Bourne-shell derivatives, multiple-word variables such as var="foo bar" are split into words when passed to a command or used in a `for foo in $var' loop. By default, zsh does not have that behaviour: the variable remains intact. (This is not a bug! See below.) An option (shwordsplit) exists to provide compatibility. For example, defining the function args to show the number of its arguments: args() { echo $#; } and with our definition of `var', args $var produces the output `1'. After setopt shwordsplit the same function produces the output `2', as with sh and ksh. Unless you need strict sh/ksh compatibility, you should ask yourself whether you really want this behaviour, as it can produce unexpected effects for variables with entirely innocuous embedded spaces. This can cause horrendous quoting problems when invoking scripts from other shells. The natural way to produce word-splitting behaviour in zsh is via arrays. For example, set -A array one two three twenty (or array=(one two three twenty) if you prefer), followed by args $array produces the output `4', regardless of the setting of shwordsplit. Arrays are also much more versatile than single strings. Probably if this mechanism had always been available there would never have been automatic word splitting in scalars, which is a sort of uncontrollable poor man's array. Note that this happens regardless of the value of the internal field separator, $IFS; in other words, with `IFS=:; foo=a:b; args $foo' you get the answer 1. Other ways of causing word splitting include a judicious use of `eval': sentence="Longtemps, je me suis couch\\'e de bonne heure." eval "words=($sentence)" after which $words is an array with the words of $sentence (note characters special to the shell, such as the `'' in this example, must already be quoted), or, less standard but more reliable, turning on shwordsplit for one variable only: args ${=sentence} always returns 8 with the above definition of `args'. (In older versions of zsh, ${=foo} toggled shwordsplit; now it forces it on.) Note also the "$@" method of word splitting is always available in zsh functions and scripts (though strictly this does array splitting, not word splitting). Shwordsplit is set when zsh is invoked with the names `ksh' or `sh', or (entirely equivalent) when `emulate ksh' or `emulate sh' is in effect. C5) Why do my autoloaded functions not autoload [the first time]? (Before version 3.0, autoloading in the Korn shell way was not allowed; this article is now a historical artefact and will eventually be removed. Note, however, that the old form of autoloading is still allowed and there are no plans to remove it.) When you put a shell function in an autoload directory (i.e. one mentioned in $FPATH), it should be written just as if it were a shell script. In other words, there should be no line at the beginning saying `function foo {' or `foo () {', and consequently no matching '}' at the end. If you include those, then the first time you try to use the function, the _whole_ file is run --- in other words, zsh simply defines the function and does nothing else. As a concrete example, if you have a function which you would define on the command line as `xhead () { print -n "\033]2;$*\a"; }' and your have assigned `FPATH=~/fns', then your .zshrc should contain `autoload xhead' and the file ~/fns/xhead should contain only `print -n "\033]2;$*\a"'. (A neat trick to autoload all functions in a given directory is to include a line like `autoload ~/fns/*(:t)' in .zshrc; the bit in parentheses removes the directory part of the filenames, leaving just the function names.) C6) How does base arithmetic work? The ksh syntax is now understood, i.e. let 'foo = 16#ff' or equivalently (( foo = 16#ff )) or even foo=$[16#ff] (note that `foo=$((16#ff))' is now supported). The original syntax was (( foo = [16]ff )) --- this was based on a misunderstanding of the ksh manual page. It still works but its use is deprecated. Then echo $foo gives the answer `255'. It is possible to declare variables explicitly to be integers, via typeset -i foo which has a different effect: namely the base used in the first assignment (hexadecimal in the example) is subsequently used whenever `foo' is displayed (although the internal representation is unchanged). To ensure foo is always displayed in decimal, declare it as typeset -i 10 foo which requests base 10 for output. You can change the output base of an existing variable in this fashion. Using the `$[ ... ]' method will always display in decimal. C7) How do I get a newline in my prompt? You can place a literal newline in quotes, i.e. PROMPT="Hi Joe, what now?%# " If you have the bad taste to set the option cshjunkiequotes, which inhibits such behaviour, you will have to bracket this with `unsetopt cshjunkiequotes' and `setopt cshjunkiequotes', or put it in your .zshrc before the option is set. Arguably the prompt code should handle `print'-like escapes. Feel free to write this :-). Otherwise, you can use PROMPT=$(print "Hi Joe,\nwhat now?%# ") in your initialisation file. C8) Why does `bindkey ^a command-name' or 'stty intr ^-' do something funny? You probably have the extendedglob option set in which case ^ and # are metacharacters. ^a matches any file except one called a, so the line is interpreted as bindkey followed by a list of files. Quote the ^ with a backslash or put quotation marks around ^a. C9) Why can't I bind \C-s and \C-q any more? The control-s and control-q keys now do flow control by default, unless you have turned this off with `stty -ixon' or redefined the keys which control it with `stty start' or `stty stop'. (This is done by the system, not zsh; the shell simply respects these settings.) In other words, \C-s stops all output to the terminal, while \C-q resumes it. There is an option NO_FLOW_CONTROL to stop zsh from allowing flow control and hence restoring the use of the keys: put `setopt noflowcontrol' in .zshrc. C10) How do I execute command `foo' within function `foo'? The command `command foo' does just that. You don't need this with aliases, but you do with functions. Note that error messages like zsh: job table full or recursion limit exceeded are a good sign that you tried calling `foo' in function `foo' without using `command'. C11) Why do history substitutions with single bangs do something funny? If you have a command like "echo !-2:$ !$", the first history substitution then sets a default to which later history substitutions with single unqualified bangs refer, so that !$ becomes equivalent to !-2:$. The option CSH_JUNKIE_HISTORY makes all single bangs refer to the last command. C12) Why does zsh kill off all my background jobs when I logout? Simple answer: you haven't asked it not to. Zsh (unlike [t]csh) gives you the option of having background jobs killed or not: the `nohup' option exists if you don't want them killed. Note that you can always run programs with `nohup' in front of the pipeline whether or not the option is set, which will prevent that job from being killed on logout. (Nohup is actually an external command.) The `disown' builtin is very useful in this respect: if zsh informs you that you have background jobs when you try to logout, you can `disown' all the ones you don't want killed when you exit. This is also a good way of making jobs you don't need the shell to know about (such as commands which create new windows) invisible to the shell. C13) How do I list all my history entries? Tell zsh to start from entry 1: `history 1'. Those entries at the start which are no longer in memory will be silently omitted. Section D: The mysteries of completion Programmable completion using the `compctl' command is one of the most powerful, and also potentially confusing, features of zsh; here I give a short introduction. There is a set of example completions supplied with the source in Misc/compctl-examples; completion definitions for many of the most obvious commands can be found there. D1) What is completion? `Completion' is where you hit a particular command key (TAB is the standard one) and the shell tries to guess the word you are typing and finish it for you --- a godsend for long file names, in particular, but in zsh there are many, many more possibilities than that. There is also a related process, `expansion', where the shell sees you have typed something which would be turned by the shell into something else, such as a variable turning into its value ($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 "CTRL-x g", which lists expansions.) Expansion is generally fairly intuitive and not under user control; for the rest of the section I will discuss completion only. D2) What sorts of things can be completed? The simplest sort is filename completion, mentioned above. Unless you have made special arrangements, as described below, then after you type a command name, anything else you type is assumed by the completion system to be a filename. If you type part of a word and hit TAB, zsh will see if it matches the first part a file name and if it does it will automatically insert the rest. The other simple type is command completion, which applies (naturally) to the first word on the line. In this case, zsh assumes the word is some command to be executed lying in your $PATH and tries to complete that. Other forms of completion have to be set up by special arrangement. See the manual entry for compctl for a list of all the flags: you can make commands complete variable names, user names, job names, etc., etc. For example, one common use is that you have an array variable, $hosts, which contains names of other machines you use frequently on the network: hosts=(fred.ph.ku.ac.uk snuggles.floppy-bunnies.com here.there.edu) then you can tell zsh that when you use telnet (or ftp, or ...), the argument will be one of those names: compctl -k hosts telnet ftp ... so that if you type `telnet fr' and hit TAB, the rest of the name will appear by itself. An even more powerful option to compctl (-g) is to tell zsh that only certain sorts of filename are allowed. The argument to -g is exactly like a glob pattern, with the usual wildcards `*', `?', etc. In the compctl statement it needs to be quoted to avoid it being turned into filenames straight away. For example, compctl -g '*.(ps|eps)' ghostview tells zsh that if you type TAB on an argument after a ghostview command, only files ending in `.ps' or `.eps' should be considered for completion. Note that flags may be combined; if you have more than one, all the possible completions for all of them are put into the same list, all of them being possible completions. So compctl -k hosts -f rcp tells zsh that rcp can have a hostname or a filename after it. (You really need to be able to handle host:file, which is where programmable completion comes in, see D4).) D3) 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 it's options. The default is for it to beep and completion to stop until you type another character. You can type ^D to see all the possible completions. This can be changed by the following options, among others: - with nobeep set, that annoying beep goes away - with nolistbeep, beeping is only turned off for ambiguous completions - with autolist set, when the completion is ambiguous you get a list without having to type ^D - with listambigous, this is modified so that nothing is listed if there is an unambiguous prefix or suffix to be inserted - with menucomplete set, one completion is always inserted completely, then when you hit TAB it changes to the next, and so on until you get back to where you started - with automenu, you only get the menu behaviour when you hit TAB again on the ambiguous completion. Combinations of these are possible; for example, autolist and automenu together give an intuitive combination. D4) How do I get started with programmable completion? Finally, the hairiest part of completion. It is possible to get zsh to consider different completions not only for different commands, but for different words of the same command, or even to look at other words on the command line (for example, if the last word was a particular flag) and decide then. There are really two sorts of things to worry about. The simpler is alternative completion: that just means zsh will try one alternative, and only if there are no possible completions try the next. For example compctl -g '*.ps' + -f lpr says that after lpr you'd prefer to find only `.ps' files, so if there are any, only those are used, but if there aren't any, any old file is a possibility. You can also have a + with no flags after it, which tells zsh that it's to treat the command like any other if nothing was found. That's only really useful if your default completion is fancy, i.e. you have done something with `compctl -D' to tell zsh how commands which aren't specially handled are to have their arguments completed. The second sort is the hard one. Following a `-x', zsh expects that the next thing will be some completion code, which is a single letter followed by an argument in square brackets. For example 'p[1]': `p' is for position, and the argument tells it to look at position 1; that says that this completion only applies to the word immediately after the command. You can also say 'p[1,3]' which says the completion only applies to the word if it's between the first and third words, inclusive, after the command, and so on. See the list in the `compctl' manual entry for a list of these conditions: some conditions take one argument in the square brackets, some two. Usually, negative numeric arguments count backwards from the end (for example, 'p[-1]' applies to the last word on the line). The condition is then followed by the flags as usual (as in D2)), and possibly other condition/flag sets following a single -; the whole lot ends with a double -- before the command name. In other words, each extended completion section looks like this: -x <pattern> <flags>... [ - <pattern> <flags>... ...] -- Let's look at rcp again: this assumes you've set up $hosts as above. This uses the `n[<n>,<string>]' flag, which tells zsh to look for the <n>'th occurrence of <string> in the word, ignoring anything up to and including that. We'll use it for completing the bits of rcp's `user@host:file' combination. (Of course, the file name is on the local machine, not `host', but let's ignore that; it may still be useful.) compctl -k hosts -S ':' + -f -x 'n[1,:]' -f - \ 'n[1,@]' -k hosts -S ':' -- rcp This means: (1) try and complete a hostname (the bit before the `+'), if successful add a `:' (-S for suffix); (2) if that fails move on to try the code after the `+': look and see if there is a `:' in a word (the `n[1,:]'); if there is, complete filenames (-f) after the first of them; (3) otherwise look for an `@' and complete hostnames after the first of them (the `n[1,@]'), adding a `:' if successful; (4) if all else fails use the -f before the `-x' and try to complete files. So the rules for order are (1) try anything before a `+' before anything after it (2) try the conditions after a -x in order until one succeeds (3) use the default flags before the -x if none of the conditions was true. Different conditions can also be combined. There are three levels of this (in decreasing order of precedence): i) multiple square brackets after a single condition give alternatives: for example, 's[foo][bar]' says apply the completion if the word begins with `foo' or `bar', ii) spaces between conditions mean both must match: for example, 'p[1] s[-]' says this completion only applies for the first word after the command and only if it begins with a `-', iii) commas between conditions mean either can match: for example, 'c[-1,-f], s[-f]' means either the previous word (-1 relative to the current one) is -f, or the current word begins with -f --- useful to use the same completion whether or not the -f has a space after it. Here's a useless example just to show a general `-x' completion. compctl -f -x 'c[-1,-u][-1,-U] p[2], s[-u]' -u - \ 'c[-1,-j]' -P % -j -- foobar The way to read this is: for command `foobar', look and see if (((the word before the current one is -u) or (the word before the current one is -U)) and (the current word is 2)) or (the current word begins with -u); if so, try to complete user names. If the word before the current one is -j, insert the prefix `%' before the current word if it's not there already and complete job names. Otherwise, just complete file names. D5) And if programmable completion isn't good enough? ...then your last resort is to write a shell function to do it for you. By combining the `-U' and `-K func' flags you can get almost unlimited power. The `-U' tells zsh that whatever the completion produces is to be used, even if it doesn't fit what's there already (so that gets deleted when the completion is inserted). The `-K func' tells zsh a function name. The function is passed what's on the line already, but it can return anything it likes via the `reply' array, and this becomes the set of possible completions. The best way to understand this is to look at `multicomp' and other functions supplied with the zsh distribution. Section Z: The future of zsh Z1) What bugs are currently known and unfixed? (Plus recent important changes) Here are some of the more well-known ones, very roughly in decreasing order of significance. Many of these can also be counted against differences from ksh in question B1); note that this applies to the latest beta version and that simple bugs are often fixed quite quickly. There is a file Etc/BUGS in the source distribution with more detail. Special variables won't be unset after e.g. `PATH=... read ...', i.e. if used with a builtin command or shell function. (According to POSIX, this is not a bug with `special' builtins.) `time' is ignored with builtins and can't be used with {...}. `set -x' (`setopt xtrace') still has a few glitches. The :q modifier doesn't split words and -q and -x don't work for variables. In vi mode, `u' can go past the original modification point. The singlelinezle option has problems with prompts containing escapes. The `r' command does not work inside $(...) or `...` expansions. Note that a few recent changes introduce incompatibilities (these are not bugs): Changes since zsh 2.5: Signal traps established with the `trap' builtin are now called with the environment of the caller, instead of as a new function level, as in ksh. Traps established as functions (e.g. `TRAPINT() {...}') work as before. The NO_CLOBBER option is now -C and PRINT_EXIT_VALUE -1; they used to be the other way around. (Use of names rather than letters is generally recommended.) `[[' is a reserved word, hence must be separated from other characters by whitespace; `{' and `}' are also reserved words if the IGNORE_BRACES option is set. The option CSH_JUNKIE_PAREN has been removed: csh-like code now always does what it looks like it does, so `if ( ... ) ...' executes the code in parentheses in a subshell. To make this useful, the syntax expected after an `if', etc., is less strict than in other shells. On the other hand, `foo=*' does not perform globbing immediately on the right hand side of the assignment; the old behaviour now requires the option GLOB_ASSIGN. (`foo=(*)' is and has always been the consistent way of doing this.) <> performs redirection of input and output to the specified file. For numeric globs, you now need <->. The command line qualifiers exec, noglob, command, - are now treated more like builtin commands: previously they were syntactically special. This should make it easier to perform tricks with them (disabling, hiding in parameters, etc.). The pushd builtin has been rewritten for compatibility with other shells. The old behavour can be achieved with a shell function. The current version now uses ~'s for directory stack substitution instead of ='s. This is for consistency: all other directory substitution (~user, ~name, ~+, ...) used a tilde, while =<number> caused problems with =program substitution. The `HISTLIT' option was broken in various ways and has been removed: the rewritten history mechanism doesn't alter history lines, making the option unnecessary. History expansion is disabled in single-quoted strings, like other forms of expansion -- hence exclamation marks there should not be backslashed. The `HISTCHARS' variable is now `histchars'. Currently both are tied together for compatibility. The PROMPT_SUBST option now performs backquote expansion -- hence you should quote these in prompts. (SPROMPT has changed as a result.) Quoting in prompts has changed: close parentheses inside ternary expressions should be quoted with a %; history is now %!, not !. Backslashes are no longer special. Z2) Where do I report bugs, get more info / who's working on zsh? The shell is being maintained by various (entirely self-appointed) subscribers to the mailing list, zsh-workers@math.gatech.edu so any suggestions, complaints, questions and matters for discussion should be sent there. If you want someone to mail you directly, say so. Most patches to zsh appear there first. Two progressively lower volume lists exist, one with messages concerning the use of zsh, zsh-users@math.gatech.edu and one just containing announcements: about releases, about major changes in the shell, or this FAQ, for example, zsh-announce@math.gatech.edu (posting to the last one is currently restricted). Note that you should only join one of these lists: people on zsh-workers receive all the lists, and people on zsh-users will also receive the announcements list. The lists are handled by an automated server. The instructions for zsh-announce and zsh-users are the same as for zsh-workers: just change zsh-workers to whatever in the following. To join zsh-workers, send email to zsh-workers-request@math.gatech.edu with the *subject* line (this is a change from the old list) subscribe <your-email-address> e.g. Subject: subscribe P.Stephenson@swansea.ac.uk and you can unsubscribe in the same way. The list maintainer, Richard Coleman, can be reached at coleman@math.gatech.edu The list from May 1992 to May 1995 is archived in ftp://ftp.sterling.com/zsh/zsh-list/YY-MM where YY-MM are the year and month in digits. Of course, you can also post zsh queries to the Usenet group comp.unix.shell; if all else fails, you could even e-mail me. Z3) What's on the wish-list? Mostly, a lot of the code needs a major clean-up: particular offenders are the history code (hist.c: this is under way), parameter code (params.c) and substitution code (subst.c). A more efficient set of code for lexing/parsing/execution might also be an advantage. Volunteers are particularly welcome for these tasks. Ksh/sh compatibility could be improved; this is a useful long term goal. Option for glob qualifiers to follow perl syntax. Binding of shell functions (or commands?) to key strokes -- requires some way of accessing the editing buffer from functions and probably of executing zle functions as a command. trap '...' FOO should be eval'd rather than called as a function. `PATH=' should clear the PATH: it inserts `.'; use `unset PATH' or `path=()' for the time being. This is not really a bug as the . would be used internally in any case (cf. ksh). Users should be able to create their own foopath/FOOPATH array/path combinations. Acknowledgments: Thanks to zsh-list, in particular Bart Schaefer, for suggestions regarding this document. Zsh has been in the hands of archivists Jim Mattson, Bas de Bakker, Richard Coleman and Zoltan Hidvegi, and the mailing list has been run by Peter Gray, Rick Ohnemus and Richard Coleman, all of whom deserve thanks. The world is eternally in the debt of Paul Falstad for inventing zsh in the first place (though the wizzo extended completion is by Sven Wischnowsky). Copyright Information: This document is copyright (C) P.W. Stephenson, 1995, 1996. This text originates in the U.K. and the author asserts his moral rights under the Copyrights, Designs and Patents Act, 1988. Permission is hereby granted, without written agreement and without license or royalty fees, to use, copy, modify, and distribute this documentation for any purpose, provided that the above copyright notice appears in all copies of this documentation. Remember, however, that this document changes monthly and it may be more useful to provide a pointer to it rather than the entire text. A suitable pointer is "information on the Z-shell can be obtained on the World Wide Web at URL http://www.mal.com/zsh/".