fish - ArchWiki

# fish

fish (the friendly interactive shell) is a user friendly command line shell intended mostly for interactive use.

## Installation

Install the fish package from the official repositories for the stable version of the mainstream fork of the project.

Install fish-shell-gitAUR from the AUR for the latest development version.

Install fish-gitAUR from the AUR for the legacy version that was discontinued by its original developer in 2011.

To make fish the default shell, run `chsh -s /usr/bin/fish`.

## Input/output

### File descriptors

Like other shells, fish lets you redirect input/output streams. This is useful when using text files to save programs output or errors, or when using text files as input. Most programs use three input/output streams, represented by numbers called file descriptors (FD). These are:

- Standard input (FD 0), used for reading (keyboard by default).
- Standard output (FD 1), used for writing (screen by default).
- Standard error (FD 2), used for displaying errors and warnings (screen by default).

### Redirection

Any file descriptor can be directed to other files through a mechanism called redirection:

    Redirecting standard input:
    $ command < source_file

    Redirecting standard output:
    $ command > destination

    Appending standard output to an existing file:
    $ command >> destination

    Redirecting standard error:
    $ command ^ destination

    Appending standard error to an existing file:
    $ command ^^ destination

You can use one of the following as `destination`:

- A filename (the output will be written to the specified file).
- An `&` followed by the number of another file descriptor. The output will be written to the other file descriptor.
- An `&` followed by a `-` sign. The output will not be written anywhere.

Examples:

    Redirecting standard output to a file:
    $ command > destination_file.txt

    Redirecting both standard output and standard error to the same file:
    $ command > destination_file.txt ^ &1

    Silencing standard output:
    $ command > &-

### Piping

You can redirect standard output of one command to standard input of the next command. This is done by separating the commands by the pipe character (`|`). Example:

    cat example.txt | head

You can redirect other file descriptors to the pipe (besides standard output). The next example shows how to use standard error of one command as standard input of another command, prepending standard error file descriptor's number and `>` to the pipe:

    $ command 2>| less

This will run `command` and redirect its standard error to the `less` command.

## Configuration

User configurations for fish are located at `~/.config/fish/config.fish`. Adding commands or functions to the file will execute/define them when opening a terminal, similar to `.bashrc`.

### Web interface

The fish prompt and terminal colors can be set with the interactive web interface:

    fish_config

Selected settings are written to your personal configuration file. You can also view defined functions and your history.

### Prompt

If you would like fish to display the branch and dirty status when you are in a git directory, you can add the following to your `~/.config/fish/config.fish`:

    # fish git prompt
    set __fish_git_prompt_showdirtystate 'yes'
    set __fish_git_prompt_showstashstate 'yes'
    set __fish_git_prompt_showupstream 'yes'
    set __fish_git_prompt_color_branch yellow

    # Status Chars
    set __fish_git_prompt_char_dirtystate '⚡'
    set __fish_git_prompt_char_stagedstate '→'
    set __fish_git_prompt_char_stashstate '↩'
    set __fish_git_prompt_char_upstream_ahead '↑'
    set __fish_git_prompt_char_upstream_behind '↓'

    function fish_prompt
            set last_status $status
            set_color $fish_color_cwd
            printf '%s' (prompt_pwd)
            set_color normal
            printf '%s ' (__fish_git_prompt)
           set_color normal
    end

### 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

### History Substitution

Fish does not implement history substitution (e.g. `sudo !!`), and the fish developers have said that they do not plan to. Still, this is an essential piece of many users' workflow. Reddit user, crossroads1112, created a function that regains some of the functionality of history substitution and with another syntax. The function is on github and instructions are included as comments in it. There is a forked version that is closer to the original syntax and allows for `command !!` if you specify the command in the helper function.

## Troubleshooting

The factual accuracy of this article or section is disputed.

Reason: Changing the default shell should not interfere with the execution of shell scripts, so long as they begin with a proper shebang line. (Discuss in Talk:Fish#)

In Arch, there are a lot of shell scripts written for Bash, and these have not been translated to fish. It is advisable not to set fish as your default shell because of this. The best 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 LilyTerm and other light terminal emulators that do not support setting the shell it would look like this:

    SHELL=/usr/bin/fish lilyterm

Another option is to set fish as the default shell for the terminal in the terminal's configuration or for a terminal profile if your terminal emulator has a profiles feature. This is contrast to changing the default shell for the user which would cause the above mentioned problem.

To set fish as the shell started in tmux, put this into your `~/.tmux.conf`:

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

Not setting fish as system wide default allows the arch scripts to run on startup, ensure the environment variables are set correctly, and generally reduces the issues associated with using a non-Bash compatible terminal like fish.

If you decide to set fish as your default shell, 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
            set PATH $PATH /usr/bin /sbin
    end

Note that you will need to manually add various other environment variables, such as `$MOZ_PLUGIN_PATH`. It is a huge amount of work to get a seamless experience with fish as your default shell.

### su launching Bash

If su starts with Bash (because Bash is the default shell), define a function in fish:

    $ funced su
    function su
            /bin/su --shell=/usr/bin/fish $argv
    end
    $ funcsave su

### 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 -eq 1
            exec startx -- -keeptty
        end
    end

Note: See this issue for reasons why `startx` requires the `-keeptty` flag when using fish.

## See also

- http://fishshell.com/ - Home page
- http://fishshell.com/docs/2.1/index.html - Documentation

Category:

- Command shells