Difference between revisions of "Fish"
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su --shell=/usr/bin/fish $argv
Revision as of 06:25, 5 December 2018
fish is intentionally not fully POSIX compliant, it aims at addressing POSIX inconsistencies (as perceived by the creators) with a simplified or a different syntax. This means that even simple POSIX compliant scripts may require some significant adaptation or even full rewriting to run with fish.
- 1 Installation
- 2 System integration
- 3 Configuration
- 4 Tips and tricks
- 4.1 Command substitution
- 4.2 Command chaining
- 4.3 Disable greeting
- 4.4 Make su launch fish
- 4.5 Start X at login
- 4.6 Use liquidprompt
- 4.7 Put git status in prompt
- 4.8 Color the hostname in the prompt in SSH
- 4.9 Evaluate ssh-agent
- 4.10 The "command not found" hook
- 4.11 Remove a process from the list of jobs
- 4.12 Set a persistent alias
- 5 See also
Install the package. For the development version, install the AUR package.
Once installed, simply type
fish to drop into the fish shell.
Documentation can be found by typing
help from fish; it will be opened in a web browser. It is recommended to read at least the "Syntax overview" section, since fish's syntax is different from many other shells.
One must decide whether fish is going to be the default user's shell, which means that the user falls directly in fish at login, or whether it is used in interactive terminal mode as a child process of the current default shell, here we will assume the latter is Bash. To elaborate on these two setups:
- fish used as the default shell: this mode requires some basic understanding of the fish functioning and its scripting language. The user's current initialization scripts and environment variables need to be migrated to the new fish environment. To configure the system in this mode, follow #Setting fish as default shell.
- fish used as an interactive shell only: this is the less disruptive mode, all the Bash initialization scripts are run as usual and fish runs on top of Bash in interactive mode connected to a terminal. To setup fish in this mode, follow #Setting fish as interactive shell only.
Setting fish as default shell
If you decide to set fish as the default user shell, the first step is to set the shell of this particular user to
/usr/bin/fish. This can be done by following the instructions in Command-line shell#Changing your default shell.
The next step is to port the current needed actions and configuration performed in the various Bash initialization scripts, namely
~/.bashrc, into the fish framework.
In particular, the content of the
$PATH environment variable, once directly logged under fish, should be checked and adjusted to one's need. In fish,
$PATH is defined as a global environment variable: it has a global scope across all functions, it is lost upon reboot and it is an environment variable which means it is exported to child processes.
The recommended way of adding permanently additional locations to the path is by assigning them to the
fish_user_paths universal variable. This variable is automatically added to
$PATH and is preserved across restarts of the shell. For example by setting:
$ set -U fish_user_paths /first/path /second/path /third/one
These three locations will be permanently prepended to the path. This is an easy way to complement the path without the need to add any instruction in scripts.
Setting fish as interactive shell only
Not setting fish as system wide or user default allows the current Bash scripts to run on startup. It ensures the current user's environment variables are unchanged and are exported to fish which then runs as a Bash child. Below are several ways of running fish in interactive mode without setting it as the default shell.
Modify .bashrc to drop into fish
Keep the default shell as Bash and simply add the line
exec fish to the appropriate Bash#Configuration files, such as
.bashrc. This will allow Bash to properly source
/etc/profile and all files in
/etc/profile.d. Because fish replaces the Bash process, exiting fish will also exit the terminal. Compared to the following options, this is the most universal solution, since it works both on a local machine and on a SSH server.
- In this setup, use
bash --norcto manually enter Bash without executing the commands from
~/.bashrcwhich would run
exec fishand drop back into fish.
- To have commands such as
bash -c 'echo test'run the command in Bash instead of starting fish, you can write
if [ -z "$BASH_EXECUTION_STRING" ]; then exec fish; fiinstead.
Use terminal emulator options
Another option is to open your terminal emulator with a command line option that executes fish. For most terminals this is the
-e switch, so for example, to open gnome-terminal using fish, change your shortcut to use:
gnome-terminal -e fish
With terminal emulators that do not support setting the shell, for exampleAUR, it would look like this:
Also, depending on the terminal, you may be able to set fish as the default shell in either the terminal configuration or the terminal profile.
Use terminal multiplexer options
To set fish as the shell started in tmux, put this into your
set-option -g default-shell "/usr/bin/fish"
Whenever you run tmux, you will be dropped into fish.
The configuration file runs at every login and is located at
~/.config/fish/config.fish. Adding commands or functions to the file will execute/define them when opening a terminal, similar to
.bashrc. Note that whenever a variable needs to be preserved, it be set as universal rather than defined in the aforementioned configuration file.
The user's functions are located in the directory
~/.config/fish/functions under the filenames
The fish terminal colors, prompt, functions, variables, history, bindings and abbreviations can be set with the interactive web interface:
fish can generate autocompletions from man pages. Completions are written to
~/.config/fish/generated_completions/ and can be generated by calling:
You can also define your own completions in
/usr/share/fish/completions/ for a few examples.
Context-aware completions for Arch Linux-specific commands like pacman, pacman-key, makepkg, cower, pbget, pacmatic are built into fish, since the policy of the fish development is to include all the existent completions in the upstream tarball. The memory management is clever enough to avoid any negative impact on resources.
Tips and tricks
fish does not implement Bash style history substitution (e.g.
sudo !!), and the developers recommend in the fish faq to use the interactive history recall interface instead: the
Up arrow recalls whole past lines and
Alt+Up recalls individual arguments.
However some workarounds are described in the fish wiki: while not providing complete history substitution, some functions replace
!! with the previous command or
!$ with the previous last argument.
|| is not implemented and the syntax to achieve similar results in fish is respectively
; and and
Some keybindings can be set for automatic substitution as described in the fish wiki.
By default, fish prints a greeting message at startup. To disable it, run once:
$ set -U fish_greeting
This clears the universal
fish_greeting variable, shared with all fish instances and which is preserved upon restart of the shell.
Make su launch fish
If su starts with Bash because Bash is the target user's (root if no username is provided) default shell, one can define a function to redirect it to fish whatever the user's shell:
function su command su --shell=/usr/bin/fish $argv end
Start X at login
Add the following to the bottom of your
# Start X at login if status is-login if test -z "$DISPLAY" -a $XDG_VTNR = 1 exec startx -- -keeptty end end
Put git status in prompt
If you would like fish to display the branch and dirty status when you are in a git directory, you can define the following
function fish_prompt set -l last_status $status if not set -q __fish_git_prompt_show_informative_status set -g __fish_git_prompt_show_informative_status 1 end if not set -q __fish_git_prompt_color_branch set -g __fish_git_prompt_color_branch brmagenta end if not set -q __fish_git_prompt_showupstream set -g __fish_git_prompt_showupstream "informative" end if not set -q __fish_git_prompt_showdirtystate set -g __fish_git_prompt_showdirtystate "yes" end if not set -q __fish_git_prompt_color_stagedstate set -g __fish_git_prompt_color_stagedstate yellow end if not set -q __fish_git_prompt_color_invalidstate set -g __fish_git_prompt_color_invalidstate red end if not set -q __fish_git_prompt_color_cleanstate set -g __fish_git_prompt_color_cleanstate brgreen end printf '%s%s %s%s%s%s ' (set_color $fish_color_host) (prompt_hostname) (set_color $fish_color_cwd) (prompt_pwd) (set_color normal) (__fish_git_prompt) if not test $last_status -eq 0 set_color $fish_color_error end echo -n '$ ' set_color normal end
More explanations about the parameters can be found in the fish-shell git.
Color the hostname in the prompt in SSH
To color the hostname in the prompt dynamically whenever connected through SSH, add the following lines in either the
fish_prompt function or the fish configuration file, here using the red color:
... if set -q SSH_TTY set -g fish_color_host brred end ...
eval (ssh-agent) generate errors due to how variables are set. To work around this, use the csh-style option
$ eval (ssh-agent -c)
The "command not found" hook
pkgfile includes a "command not found" hook that will automatically search the official repositories, when entering an unrecognized command. This hook will be run by default if is installed.
Remove a process from the list of jobs
fish terminates any jobs put into the background when fish terminates. To keep a job running after fish terminates, first use the
disown builtin. For example, the following starts
firefox in the background and then disowns it:
$ firefox & $ disown
This means firefox will not be closed when the fish process is closed. Seein fish for more details.
Set a persistent alias
To quickly make a persistent alias, one can simply use the method showed in this example:
$ alias lsl "ls -l" $ funcsave lsl
This will create the function:
function lsl ls -l $argv end
and will set the alias as a persistent shell function. To see all functions and/or edit them, one can simply use
fish_config and look into the Function tab in the web configuration page.
For more detailed information, refer to fish - alias.