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# Chapter 1: Introducing zsh and how to install it

## 1.1: Sources of information

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

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

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

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

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

I have 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: https://zsh.sourceforge.io/Guide/

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

For any more eclectic information, you should contact the mailing list: see question 6.2.

## 1.2: What is it?

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

It was written by Paul Falstad when a student at Princeton; however, Paul doesn't maintain it any more and enquiries should be sent to the mailing list (see question 6.2). Zsh is distributed under a standard Berkeley style copyright.

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

## 1.3: What is it good at?

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

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

## 1.4: On what machines will it run?

From version 3.0, zsh uses GNU autoconf as the installation mechanism. This considerably increases flexibility over the old `buildzsh' mechanism. Consequently, zsh should compile and run on any modern version of UNIX, and a great many not-so-modern versions too. The file 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 6.2). Please make sure you have the latest version first.

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

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

## 1.5: 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 `development` subdirectory.

Note also that as the shell changes, it may become incompatible with older versions; see the end of question 6.1 for a partial list. Changes of this kind are almost always forced by an awkward or unnecessary feature in the original design (as perceived by current users), or to enhance compatibility with other Bourne shell derivatives, or (mostly in the 3.0 series) to provide POSIX compliance.

## 1.6: Where do I get it?

The coordinator of development is currently me; the alias coordinator@zsh.org can be used to contact whoever is in the hot seat. 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 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 http://www.cygwin.com/. Please 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 1.1) at:

https://zsh.sourceforge.io/Patches/

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

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

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

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

        [ -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.

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