Difference between revisions of "Fish"

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[[Category:Command shells (English)]]
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{{lowercase title}}
 +
[[Category:Command shells]]
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[[de:Fish]]
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[[ja:Fish]]
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[[ru:Fish]]
 +
[[zh-hans:Fish]]
  
{{i18n_links_start}}
+
[https://fishshell.com fish], the '''''f'''riendly '''i'''nteractive '''sh'''ell'', is a [[command-line shell|commandline shell]] intended to be interactive and user-friendly.
{{i18n_entry|Deutsch|fish (Deutsch)}}
 
{{i18n_entry|English|fish}}
 
{{i18n_links_end}}
 
  
{{Article summary start}}
+
''fish'' is intentionally not fully [[Wikipedia:POSIX|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.
{{Article summary heading|Available Languages}}
 
{{i18n_entry|Deutsch|fish (Deutsch)}}
 
{{i18n_entry|English|fish}}
 
{{Article summary end}}
 
  
== Introduction ==
+
== Installation ==
'''fish''' is a user friendly commandline shell intended mostly for interactive use.
 
  
== Installation instructions ==
+
[[Install]] the {{Pkg|fish}} package. For the development version, install the {{AUR|fish-git}} package.
To install the package for fish using pacman (the package is in the community repo)
 
run:
 
# pacman -S fish
 
  
To verify that it has been installed you can run:
+
Once installed, simply type {{ic|fish}} to drop into the fish shell.
$ less /etc/shells
 
  
If you wanted to make fish your default shell run:
+
Documentation can be found by typing {{ic|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.
$ chsh -s /usr/bin/fish
 
  
== Pacman and fish ==
+
== System integration ==
Context-aware completions for pacman and makepkg 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.
 
  
== Troubleshooting ==
+
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:
After you change your default shell to fish, you may find that you no longer have very much in your path.
 
You can add a section to your ~/.config/fish/config.fish file that will set your path correctly on login. This is much like .profile or .bash_profile as it is only executed for login shells.
 
  
  if status --is-login
+
* 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]].
    set PATH $PATH /usr/bin /sbin
+
 
end
+
* 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 {{ic|/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 {{ic|/etc/profile}}, {{ic|~/.bash_profile}}, {{ic|/etc/bash.bashrc}} and {{ic|~/.bashrc}}, into the fish framework.
 +
 
 +
In particular, the content of the {{ic|$PATH}} environment variable, once directly logged under fish, should be checked and adjusted to one's need. In fish, {{ic|$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 {{ic|fish_user_paths}} universal variable. This variable is automatically added to {{ic|$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 {{ic|exec fish}} to the appropriate [[Bash#Configuration files]], such as {{ic|.bashrc}}. This will allow Bash to properly source {{ic|/etc/profile}} and all files in {{ic|/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.
 +
 
 +
{{Tip|
 +
* In this setup, use {{ic|bash --norc}} to manually enter Bash without executing the commands from {{ic|~/.bashrc}} which would run {{ic|exec fish}} and drop back into fish.
 +
* To have commands such as {{ic|bash -c 'echo test'}} run the command in Bash instead of starting fish, you can write {{ic|if [ -z "$BASH_EXECUTION_STRING" ]; then exec fish; fi}} instead.}}
 +
 
 +
==== 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 {{ic|-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 example {{aur|lilyterm-git}}, it would look like this:
 +
 
 +
SHELL=/usr/bin/fish lilyterm
 +
 
 +
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 {{ic|~/.tmux.conf}}:
 +
 
 +
set-option -g default-shell "/usr/bin/fish"
 +
 
 +
Whenever you run ''tmux'', you will be dropped into fish.
 +
 
 +
== Configuration ==
 +
 
 +
The configuration file runs at every login and is located at {{ic|~/.config/fish/config.fish}}. Adding commands or functions to the file will execute/define them when opening a terminal, similar to {{ic|.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 {{ic|~/.config/fish/functions}} under the filenames {{ic|''function_name''.fish}}.
 +
 
 +
=== Web interface ===
 +
 
 +
The fish terminal colors, prompt, functions, variables, history, bindings and abbreviations can be set with the interactive web interface:
 +
 
 +
fish_config
 +
 
 +
=== Command completion ===
 +
 
 +
fish can generate autocompletions from man pages. Completions are written to {{ic|~/.config/fish/generated_completions/}} and can be generated by calling:
 +
 
 +
fish_update_completions
 +
 
 +
You can also define your own completions in {{ic|~/.config/fish/completions/}}. See {{ic|/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==
 +
 
 +
===Command substitution===
 +
''fish'' does not implement Bash style history substitution (e.g. {{ic|sudo !!}}), and the developers recommend in the [http://fishshell.com/docs/current/faq.html#faq-history fish faq] to use the interactive history recall interface instead: the {{ic|Up}} arrow recalls whole past lines and {{ic|Alt+Up}} recalls individual arguments.
 +
 
 +
However some workarounds are described in the [https://github.com/fish-shell/fish-shell/wiki/Bash-Style-Command-Substitution-and-Chaining-(!!-!$-&&-%7C%7C) fish wiki]: while not providing complete history substitution, some functions replace {{ic|!!}} with the previous command or {{ic|!$}} with the previous last argument.
 +
 
 +
===Command chaining===
 +
Command chaining {{ic|&&}} and {{ic|{{!}}{{!}}}} is not implemented and the syntax to achieve similar results in ''fish'' is respectively {{ic|; and}} and {{ic|; or}}.
 +
Some keybindings can be set for automatic substitution as described in the [https://github.com/fish-shell/fish-shell/wiki/Bash-Style-Command-Substitution-and-Chaining-(!!-!$-&&-%7C%7C)#getting--and- fish wiki].
 +
 
 +
===Disable greeting===
 +
 
 +
By default, fish prints a greeting message at startup. To disable it, run once:
 +
 
 +
  $ set -U fish_greeting
 +
 
 +
This clears the universal {{ic|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:
 +
{{hc|~/.config/fish/functions/su.fish|2=
 +
function su
 +
  command su --shell=/usr/bin/fish $argv
 +
end}}
 +
 
 +
=== Start X at login ===
 +
 
 +
Add the following to the bottom of your {{ic|~/.config/fish/config.fish}}.
 +
 
 +
{{bc|1=<nowiki>
 +
# Start X at login
 +
if status is-login
 +
    if test -z "$DISPLAY" -a $XDG_VTNR = 1
 +
        exec startx -- -keeptty
 +
    end
 +
end
 +
</nowiki>}}
 +
 
 +
=== Use liquidprompt ===
 +
 
 +
[https://github.com/nojhan/liquidprompt Liquidprompt] is a popular "full-featured & carefully designed adaptive prompt for Bash & Zsh" and has no plans to make it compatible with fish [https://github.com/nojhan/liquidprompt/pull/230]. [https://github.com/wesbarnett/fish-lp This project] implements it for fish.
 +
 
 +
=== 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 {{ic|fish_prompt}} function:
 +
{{hc|~/.config/fish/functions/fish_prompt.fish|
 +
<nowiki>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
 +
</nowiki>}}
 +
More explanations about the parameters can be found in the [https://github.com/fish-shell/fish-shell/blob/master/share/functions/__fish_git_prompt.fish 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 {{ic|fish_prompt}} function or the fish configuration file, here using the red color:
 +
 
 +
{{hc|~/.config/fish/functions/fish_prompt.fish|
 +
...
 +
if set -q SSH_TTY
 +
  set -g fish_color_host brred
 +
end
 +
...}}
 +
 
 +
=== Evaluate ssh-agent ===
 +
 
 +
In fish, {{ic|eval (ssh-agent)}} generate errors due to how variables are set. To work around this, use the csh-style option {{ic|-c}}:
 +
 
 +
  $ 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 {{Pkg|pkgfile}} 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 {{ic|disown}} builtin. For example, the following starts {{ic|firefox}} in the background and then disowns it:
 +
 
 +
  $ firefox &
 +
  $ disown
 +
 
 +
This means firefox will not be closed when the fish process is closed. See {{man|1|disown|url=}} in ''fish'' for more details.
  
== Licenses ==
+
=== Set a persistent alias ===
Fish Copyright (C) 2005-2006 Axel Liljencrantz.
 
  
Fish is released under the GNU General Public License, version 2.
+
To quickly make a persistent alias, one can simply use the method showed in this example:
 +
$ alias lsl "ls -l"
 +
$ funcsave lsl
  
Fish contains code under the BSD license, namely versions of the two functions strlcat and strlcpy, modified for use with wide character strings. This code is copyrighted by Todd C. Miller.
+
This will create the function:
 +
function lsl
 +
    ls -l $argv
 +
end
  
The XSel command, written and copyrighted by Conrad Parker, is distributed together with, and used by fish. It is released under the MIT license.
+
and will set the alias as a persistent shell function. To see all functions and/or edit them, one can simply use {{ic|fish_config}} and look into the ''Function'' tab in the web configuration page.
  
The xdgmime library, written and copyrighted by Red Hat, Inc, is used by the mimedb command, which is a part of fish. It is released under the LGPL.
+
For more detailed information, refer to [https://fishshell.com/docs/current/commands.html#alias fish - alias].
  
Fish contains code from the glibc library, namely the wcstok function. This code is licensed under the LGPL.
+
== See also ==
  
== External Links ==
+
* http://fishshell.com/ - Home page
*[http://www.fishshell.org HomePage]
+
* http://fishshell.com/docs/current/index.html - Documentation
*[http://www.fishshell.org/user_doc/index.html Documentation]
+
* http://hyperpolyglot.org/unix-shells - Shell grammar correspondence table
 +
* https://github.com/fish-shell/fish-shell - fish on GitHub

Latest revision as of 06:25, 5 December 2018

fish, the friendly interactive shell, is a commandline shell intended to be interactive and user-friendly.

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.

Installation

Install the fish package. For the development version, install the fish-gitAUR 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.

System integration

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 /etc/profile, ~/.bash_profile, /etc/bash.bashrc and ~/.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.

Tip:
  • In this setup, use bash --norc to manually enter Bash without executing the commands from ~/.bashrc which would run exec fish and 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; fi instead.

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 example lilyterm-gitAUR, it would look like this:

SHELL=/usr/bin/fish lilyterm

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 ~/.tmux.conf:

set-option -g default-shell "/usr/bin/fish"

Whenever you run tmux, you will be dropped into fish.

Configuration

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 function_name.fish.

Web interface

The fish terminal colors, prompt, functions, variables, history, bindings and abbreviations can be set with the interactive web interface:

fish_config

Command completion

fish can generate autocompletions from man pages. Completions are written to ~/.config/fish/generated_completions/ and can be generated by calling:

fish_update_completions

You can also define your own completions in ~/.config/fish/completions/. See /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

Command substitution

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.

Command chaining

Command chaining && and || is not implemented and the syntax to achieve similar results in fish is respectively ; and and ; or. Some keybindings can be set for automatic substitution as described in the fish wiki.

Disable greeting

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:

~/.config/fish/functions/su.fish
function su
   command su --shell=/usr/bin/fish $argv
end

Start X at login

Add the following to the bottom of your ~/.config/fish/config.fish.

# Start X at login
if status is-login
    if test -z "$DISPLAY" -a $XDG_VTNR = 1
        exec startx -- -keeptty
    end
end

Use liquidprompt

Liquidprompt is a popular "full-featured & carefully designed adaptive prompt for Bash & Zsh" and has no plans to make it compatible with fish [1]. This project implements it for fish.

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 fish_prompt function:

~/.config/fish/functions/fish_prompt.fish
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:

~/.config/fish/functions/fish_prompt.fish
...
if set -q SSH_TTY
  set -g fish_color_host brred
end
...

Evaluate ssh-agent

In fish, eval (ssh-agent) generate errors due to how variables are set. To work around this, use the csh-style option -c:

 $ 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 pkgfile 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. See disown(1) in 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.

See also