Difference between revisions of "Zsh"

Revision as of 13:44, 20 April 2012

Zsh is a powerful shell that operates as both an interactive shell and as a scripting language interpreter. While being compatible with Bash (not by default, only if you issue "emulate sh"), it offers many advantages such as:

• Faster
• Improved tab completion
• Improved globbing
• Improved array handling
• Fully customisable

The Zsh FAQ offers more reasons to use Zsh as your shell.

Installation

Before starting you may want to see what shell is currently being used:

$ echo $SHELL

Install the zsh package available in the official repositories.

Initial configuration

Make sure that Zsh has been installed correctly by running the following in a terminal:

$ zsh

You should now see zsh-newuser-install, which will walk you through some basic configuration. If you want to skip this, press q.

Making Zsh your default shell

If the shell is listed in /etc/shells you can use the chsh command to change your default shell without root access. If you installed Zsh from the official repositories, it should already have an entry in /etc/shells.

Change the default shell for the current user:

$ chsh -s $(which zsh)

After logging back in, you should notice Zsh's prompt, which by default looks different from Bash's. However you can verify that Zsh is the current shell by issuing:

$ echo $SHELL

Configuration files

At login, Zsh sources the following files in this order:

/etc/profile

This file is sourced by all Bourne-compatible shells upon login: it sets up an environment upon login and application-specific (/etc/profile.d/*.sh) settings.

~/.zshenv

This file should contain commands to set the command search path, plus other important environment variables; it should not contain commands that produce output or assume the shell is attached to a tty.

~/.zprofile

This file is generally used for automatic execution of user's scripts.

~/.zshrc

This is Zsh's main configuration file.

~/.zlogin

This file is generally used for automatic execution of user's scripts.

At logout it sources ~/.zlogout, which is used for automatic execution of user's scripts.

~/.zshrc configuration

Although Zsh is usable out of the box, it is almost certainly not set up the way you would like to use it, but due to the sheer amount of customisation available in Zsh, configuring Zsh can be a daunting and time-consuming experience.

Included below is a sample configuration file, it provides a decent set of default options as well as giving examples of many ways that Zsh can be customised. In order to use this configuration save it as a file named .zshrc. You can then apply the changes without needing to logout and then back in by running:

$ source ~/.zshrc

Simple .zshrc

Here is a simple .zshrc, that should be sufficient to get you started:

~/.zshrc

autoload -U compinit promptinit
compinit
promptinit
 
# This will set the default prompt to the walters theme
prompt walters

Command Completion

Perhaps the most compelling feature of Zsh is its advanced autocompletion abilities. At the very least, you will want to enable autocompletion in your .zshrc. To enable autocompletion, add the following to:

~/.zshrc

autoload -U compinit
compinit

The above configuration includes ssh/scp/sftp hostnames completion but in order for this feature to work you will need to prevent ssh from hashing hosts names in ~/.ssh/known_hosts (Warning: be aware that this makes your computer vulnerable to "Island-hopping" attacks). In that intention, comment the following line or set the value to "no":

/etc/ssh/ssh_config

#HashKnownHosts yes

And move your ~/.ssh/known_hosts somewhere else so that ssh creates a new one with with un-hashed hostnames (warning: previously known hosts will thus be lost).

For autocompletion with an arrow-key driven interface, add the following to:

~/.zshrc

zstyle ':completion:*' menu select

For autocompletion of command line switches for aliases, add the following to:

~/.zshrc

setopt completealiases

Key Bindings

Zsh does not use readline, instead it uses its own and more powerful zle. It does not read /etc/inputrc or ~/.inputrc. zle has an emacs mode and a vi mode. By default, it tries to guess whether you want emacs or vi keys from the $EDITOR environment variable. If it is empty, it will default to emacs. You can change this with bindkey -v or bindkey -e.

To get some special keys working:

~/.zshrc

bindkey "\e[1~" beginning-of-line # Home
bindkey "\e[4~" end-of-line # End
bindkey "\e[5~" beginning-of-history # PageUp
bindkey "\e[6~" end-of-history # PageDown
bindkey "\e[2~" quoted-insert # Ins
bindkey "\e[3~" delete-char # Del
bindkey "\e[5C" forward-word
bindkey "\eOc" emacs-forward-word
bindkey "\e[5D" backward-word
bindkey "\eOd" emacs-backward-word
bindkey "\e\e[C" forward-word
bindkey "\e\e[D" backward-word
bindkey "\e[Z" reverse-menu-complete # Shift+Tab
# for rxvt
bindkey "\e[7~" beginning-of-line # Home
bindkey "\e[8~" end-of-line # End
# for non RH/Debian xterm, can't hurt for RH/Debian xterm
bindkey "\eOH" beginning-of-line
bindkey "\eOF" end-of-line
# for freebsd console
bindkey "\e[H" beginning-of-line
bindkey "\e[F" end-of-line
# for guake
bindkey "\eOF" end-of-line
bindkey "\eOH" beginning-of-line
bindkey "^[[1;5D" backward-word
bindkey "^[[1;5C" forward-word
bindkey "\e[3~" delete-char # Del

History search

You can add these lines to your .zshrc

~/.zshrc

bindkey "^[[A" history-beginning-search-backward
bindkey "^[[B" history-beginning-search-forward

Doing this, only past commands beginning with the current input would have been shown.

Prompts

There is a quick and easy way to set up a colored prompt in Zsh. Make sure that prompt is set to autoload in your .zshrc. This can be done by adding these lines to:

~/.zshrc

autoload -U promptinit
promptinit

You can now see available prompts by running the command:

$ prompt -l

To try one of the commands that is listed, use the command prompt followed by the name of the prompt you like. For example, to use the "walters" prompt, you would enter:

$ prompt walters

Customizing your prompt

In case you are dissatisfied with the prompts mentioned above(or want to expand their usefulness), zsh offers the possibility to build your own custom prompt. Zsh supports a left- and right-sided prompt additional to the single, left-sided prompt that is common to all shells. To customize it, the following variables can be used:

Prompt variables

General

 %n 

The username

 %m 

The computer's hostname(truncated to the first period)

 %M 

The computer's hostname

 %l 

The current tty

 %? 

The return code of the last-run application.

 %# 

The prompt based on user privileges (# for root and % for the rest)

Times

 %T 

System time(HH:MM)

 %* 

System time(HH:MM:SS)

 %D 

System date(YY-MM-DD)

Directories

 %~ 

The current working directory. If you are in you are in your $HOME, this will be replaced by ~.

 %d 

The current working directory.

For the options mentioned above: You can prefix an integer to show only certain parts of your working path. If you entered %1d and found yourself in /usr/bin it would show bin. This can also be done with negative integers: %-1d using the same directory as above would show /.

Formatting

 %U [...] %u 

Begin and end underlined print

 %B [...] %b 

Begin and end bold print

 %{ [...] %} 

Begin and enter area that will not be printed. Useful for setting colors.

In fact, this tag forces Zsh to ignore anything inside them when making indents for the prompt as well.

As such, not to use it can have some weird effects on the margins and indentation of the prompt.

Colors

Zsh has a different approach to setting colors on the terminal than the one depicted here. First you write in your .zshrc:

autoload -U colors && colors

Following commands would now produce the color escape sequence needed to set the requested color when the prompt is printed:

$fg[color] 

will set the text color (red, green, blue, etc.)

$reset_color 

will reset the text color to white

It is useful to put these color commands inside %{ [...] %} , so the shell knows there is no output from these sequences and the cursor hasn't moved.

Possible color values

Example

To have a two-sided prompt you could write:

PROMPT="%{$fg[red]%}%n%{$reset_color%}@%{$fg[blue]%}%m %{$fg[yellow]%}%1~ %{$reset_color%}%#"
RPROMPT="[%{$fg[yellow]%}%?%{$reset_color%}]"

It would equal(without colors):

username@host ~ %                                                         [0]

Sample .zshrc files

Here is a list of .zshrc files. Feel free to add your own:

• Oh-my-zsh Plugin and Theme system for Zsh can help you manage your zshrc file and has a huge community of over 1400 forks on github;
• Basic setup, with dynamic prompt and window title/hardinfo => http://github.com/MrElendig/dotfiles-alice/blob/master/.zshrc;
• An Arch package named grml-zsh-config comes from http://grml.org/zsh and provides a zshrc file that includes many tweaks for your zshell.
• https://github.com/slashbeast/things/blob/master/configs/DOTzshrc - zshrc with multiple features, be sure to check out comments into it. Notable features: confirm function to ensure that user wnat to run poweroff, reboot or hibernate, support for GIT in prompt (done without vcsinfo), tab completion with menu, printing current executed command into window's title bar and more.

Global configuration

Occasionally you might want to have some settings applied globally to all zsh users. The zsh wiki tells us that there are some global configuration files, for example /etc/zshrc. This however is slightly different on ArchLinux, since it has been compiled with flags specifically to target /etc/zsh/ instead.

So, for global configuration use /etc/zsh/zshrc, not /etc/zshrc. The same goes for /etc/zsh/zshenv, /etc/zsh/zlogin and /etc/zsh/zlogout. Note that these files are not installed by default, so you need to create them yourself if you want to use them.

The only exception is zprofile, use /etc/profile instead.

Autostarting applications

Zsh always executes /etc/zsh/zshenv and $ZDOTDIR/.zshenv so do not bloat these files.

If the shell is a login shell, commands are read from /etc/profile and then $ZDOTDIR/.zprofile. Then, if the shell is interactive, commands are read from /etc/zsh/zshrc and then $ZDOTDIR/.zshrc. Finally, if the shell is a login shell, /etc/zsh/zlogin and $ZDOTDIR/.zlogin are read.

Uninstallation

If you decide that Zsh is not the shell for you and you want to return to Bash, you must first change your default shell back to Bash, before removing the Zsh package.

Follow, Zsh#Making Zsh your default shell to change the default shell back to Bash, just replace zsh with bash.

Now you can safely remove the Zsh package.

If you did not follow the above, you can still change the default shell back to Bash by editing /etc/passwd as root.

For example:

from:

username:x:1000:1000:Full Name,,,:/home/username:/bin/zsh

to:

username:x:1000:1000:Full Name,,,:/home/username:/bin/bash

External Resources

• Zsh Introduction
• Users Guide
• Zsh Docs (you can choose a different format for the doc in http://zsh.sourceforge.net/Doc/)
• Zsh FAQ
• Zsh Wiki
• Zsh-lovers
• Bash2Zsh Reference Card
• Oh My Zshell by Robby Russell
• Gentoo zsh wiki article
• Setting up the zsh prompt

• IRC channel: #zsh at irc.freenode.org