Fish is a fully-equipped command line shell (like bash or zsh) that is smart and user-friendly. Fish supports powerful features like syntax highlighting, autosuggestions, and tab completions that just work, with nothing to learn or configure.
If you want to make your command line more productive, more useful, and more fun, without learning a bunch of arcane syntax and configuration options, then fish might be just what you're looking for!
Once installed, just type in
fish into your current shell to try it out!
You will be greeted by the standard fish prompt, which means you are all set up and can start using fish:
> fish Welcome to fish, the friendly interactive shell Type help for instructions on how to use fish you@hostname ~>
This prompt that you see above is the fish default prompt: it shows your username, hostname, and working directory. - to change this prompt see how to change your prompt - to switch to fish permanently see switch your default shell to fish.
From now on, we'll pretend your prompt is just a
> to save space.
This tutorial assumes a basic understanding of command line shells and Unix commands, and that you have a working copy of fish.
If you have a strong understanding of other shells, and want to know what fish does differently, search for the magic phrase unlike other shells, which is used to call out important differences.
Fish runs commands like other shells: you type a command, followed by its arguments. Spaces are separators:
> echo hello world hello world
This runs the command
echo with the arguments
You can include a literal space in an argument with a backslash, or by using single or double quotes:
> mkdir My\ Files > cp ~/Some\ File 'My Files' > ls "My Files" Some File
Commands can be chained with semicolons.
Fish has excellent help and man pages. Run
help to open help in a web browser, and
man to open it in a man page. You can also ask for help with a specific command, for example,
help set to open in a web browser, or
man set to see it in the terminal.
> man set set - handle shell variables Synopsis...
You'll quickly notice that fish performs syntax highlighting as you type. Invalid commands are colored red by default:
A command may be invalid because it does not exist, or refers to a file that you cannot execute. When the command becomes valid, it is shown in a different color:
Valid file paths are underlined as you type them:
> cat ~/somefi
This tells you that there exists a file that starts with
somefi, which is useful feedback as you type.
These colors, and many more, can be changed by running
fish_config, or by modifying color variables directly.
Fish supports the familiar wildcard
*. To list all JPEG files:
> ls *.jpg lena.jpg meena.jpg santa maria.jpg
You can include multiple wildcards:
> ls l*.p* lena.png lesson.pdf
Especially powerful is the recursive wildcard ** which searches directories recursively:
> ls /var/**.log /var/log/system.log /var/run/sntp.log
If that directory traversal is taking a long time, you can Control+C out of it.
Pipes and Redirections¶
You can pipe between commands with the usual vertical bar:
> echo hello world | wc 1 2 12
stdin and stdout can be redirected via the familiar
>. stderr is redirected with a
> grep fish < /etc/shells > ~/output.txt 2> ~/errors.txt
To redirect stdout and stderr into one file, you need to first redirect stdout, and then stderr into stdout:
> make > make_output.txt 2>&1
As you type fish will suggest commands to the right of the cursor, in gray. For example:
It knows about paths and options:
> grep --ignore-case
And history too. Type a command once, and you can re-summon it by just typing a few letters:
> rsync -avze ssh . firstname.lastname@example.org:/some/long/path/doo/dee/doo/dee/doo
To accept the autosuggestion, hit → (right arrow) or Control+F. To accept a single word of the autosuggestion, Alt+→ (right arrow). If the autosuggestion is not what you want, just ignore it.
A rich set of tab completions work "out of the box".
Press Tab and fish will attempt to complete the command, argument, or path:
> /priTab => /private/
If there's more than one possibility, it will list them:
> ~/stuff/sTab ~/stuff/script.sh (Executable, 4.8kB) ~/stuff/sources/ (Directory)
Hit tab again to cycle through the possibilities.
fish can also complete many commands, like git branches:
> git merge prTab => git merge prompt_designer > git checkout bTab builtin_list_io_merge (Branch) builtin_set_color (Branch) busted_events (Tag)
Try hitting tab and see what fish can do!
Like other shells, a dollar sign performs variable substitution:
> echo My home directory is $HOME My home directory is /home/tutorial
Variable substitution also happens in double quotes, but not single quotes:
> echo "My current directory is $PWD" My current directory is /home/tutorial > echo 'My current directory is $PWD' My current directory is $PWD
Unlike other shells, fish has no dedicated
VARIABLE=VALUE syntax for setting variables. Instead it has an ordinary command:
set, which takes a variable name, and then its value.
> set name 'Mister Noodle' > echo $name Mister Noodle
(Notice the quotes: without them,
Noodle would have been separate arguments, and
$name would have been made into a list of two elements.)
Unlike other shells, variables are not further split after substitution:
> mkdir $name > ls Mister Noodle
In bash, this would have created two directories "Mister" and "Noodle". In fish, it created only one: the variable had the value "Mister Noodle", so that is the argument that was passed to
mkdir, spaces and all. Other shells use the term "arrays", rather than lists.
You can erase (or "delete") a variable with
> set -e MyVariable > env | grep MyVariable (no output)
Exports (Shell Variables)¶
Sometimes you need to have a variable available to an external command, often as a setting. For example many programs like
man read the
$PAGER variable to figure out your preferred pager (the program that lets you scroll text). Other variables used like this include
$LANG (to configure your language) and
$PATH. You'll note these are written in ALLCAPS, but that's just a convention.
To give a variable to an external command, it needs to be "exported". Unlike other shells, fish does not have an export command. Instead, a variable is exported via an option to
--export or just
> set -x MyVariable SomeValue > env | grep MyVariable MyVariable=SomeValue
It can also be unexported with
This works the other way around as well! If fish is started by something else, it inherits that parents exported variables. So if your terminal emulator starts fish, and it exports
$LANG set to
en_US.UTF-8, fish will receive that setting. And whatever started your terminal emulator also gave it some variables that it will then pass on unless it specifically decides not to. This is how fish usually receives the values for things like
$TERM, without you having to specify them again.
Note that exported variables can be local or global or universal - "exported" is not a scope. Usually you'd make them global via
set -gx MyVariable SomeValue.
set command above used quotes to ensure that
Mister Noodle was one argument. If it had been two arguments, then
name would have been a list of length 2. In fact, all variables in fish are really lists, that can contain any number of values, or none at all.
Some variables, like
$PWD, only have one value. By convention, we talk about that variable's value, but we really mean its first (and only) value.
Other variables, like
$PATH, really do have multiple values. During variable expansion, the variable expands to become multiple arguments:
> echo $PATH /usr/bin /bin /usr/sbin /sbin /usr/local/bin
Variables whose name ends in "PATH" are automatically split on colons to become lists. They are joined using colons when exported to subcommands. This is for compatibility with other tools, which expect $PATH to use colons. You can also explicitly add this quirk to a variable with
set --path, or remove it with
Lists cannot contain other lists: there is no recursion. A variable is a list of strings, full stop.
Get the length of a list with
> count $PATH 5
You can append (or prepend) to a list by setting the list to itself, with some additional arguments. Here we append /usr/local/bin to $PATH:
> set PATH $PATH /usr/local/bin
You can access individual elements with square brackets. Indexing starts at 1 from the beginning, and -1 from the end:
> echo $PATH /usr/bin /bin /usr/sbin /sbin /usr/local/bin > echo $PATH /usr/bin > echo $PATH[-1] /usr/local/bin
You can also access ranges of elements, known as "slices":
> echo $PATH[1..2] /usr/bin /bin > echo $PATH[-1..2] /usr/local/bin /sbin /usr/sbin /bin
You can iterate over a list (or a slice) with a for loop:
> for val in $PATH echo "entry: $val" end entry: /usr/bin/ entry: /bin entry: /usr/sbin entry: /sbin entry: /usr/local/bin
> set a 1 2 3 > set 1 a b c > echo $a$1 1a 2a 3a 1b 2b 3b 1c 2c 3c > echo $a" banana" 1 banana 2 banana 3 banana > echo "$a banana" 1 2 3 banana
This is similar to Brace expansion.
Command substitutions use the output of one command as an argument to another. Unlike other shells, fish does not use backticks `` for command substitutions. Instead, it uses parentheses:
> echo In (pwd), running (uname) In /home/tutorial, running FreeBSD
A common idiom is to capture the output of a command in a variable:
> set os (uname) > echo $os Linux
Command substitutions are not expanded within quotes. Instead, you can temporarily close the quotes, add the command substitution, and reopen them, all in the same argument:
> touch "testing_"(date +%s)".txt" > ls *.txt testing_1360099791.txt
Unlike other shells, fish does not split command substitutions on any whitespace (like spaces or tabs), only newlines. This can be an issue with commands like
pkg-config that print what is meant to be multiple arguments on a single line. To split it on spaces too, use
> printf '%s\n' (pkg-config --libs gio-2.0) -lgio-2.0 -lgobject-2.0 -lglib-2.0 > printf '%s\n' (pkg-config --libs gio-2.0 | string split -n " ") -lgio-2.0 -lgobject-2.0 -lglib-2.0
Separating Commands (Semicolon)¶
Like other shells, fish allows multiple commands either on separate lines or the same line.
To write them on the same line, use the semicolon (";"). That means the following two examples are equivalent:
echo fish; echo chips # or echo fish echo chips
When a command exits, it returns a status code as a non-negative integer.
Unlike other shells, fish stores the exit status of the last command in
$status instead of
> false > echo $status 1
This indicates how the command fared - 0 usually means success, while the others signify kinds of failure. For instance fish's
set --query returns the number of variables it queried that weren't set -
set --query PATH usually returns 0,
set --query arglbargl boogagoogoo usually returns 2.
There is also a
$pipestatus list variable for the exit statuses 1 of processes in a pipe.
or "stati" if you prefer, or "statūs" if you've time-travelled from ancient Rome or work as a latin teacher
Combiners (And, Or, Not)¶
fish supports the familiar
|| to combine commands, and
! to negate them:
> ./configure && make && sudo make install
make is only executed if
./configure succeeds (returns 0), and
sudo make install is only executed if both
> cp file1 file1_bak && cp file2 file2_bak; and echo "Backup successful"; or echo "Backup failed" Backup failed
As mentioned in the section on the semicolon, this can also be written in multiple lines, like so:
cp file1 file1_bak && cp file2 file2_bak and echo "Backup successful" or echo "Backup failed"
Conditionals (If, Else, Switch)¶
if grep fish /etc/shells echo Found fish else if grep bash /etc/shells echo Found bash else echo Got nothing end
To compare strings or numbers or check file properties (whether a file exists or is writeable and such), use test, like
if test "$fish" = "flounder" echo FLOUNDER end # or if test "$number" -gt 5 echo $number is greater than five else echo $number is five or less end # or # This test is true if the path /etc/hosts exists # - it could be a file or directory or symlink (or possibly something else). if test -e /etc/hosts echo We most likely have a hosts file else echo We do not have a hosts file end
Combiners can also be used to make more complex conditions, like
if grep fish /etc/shells; and command -sq fish echo fish is installed and configured end
There is also a switch command:
switch (uname) case Linux echo Hi Tux! case Darwin echo Hi Hexley! case FreeBSD NetBSD DragonFly echo Hi Beastie! case '*' echo Hi, stranger! end
Note that case does not fall through, and can accept multiple arguments or (quoted) wildcards.
A fish function is a list of commands, which may optionally take arguments. Unlike other shells, arguments are not passed in "numbered variables" like
$1, but instead in a single list
$argv. To create a function, use the function builtin:
> function say_hello echo Hello $argv end > say_hello Hello > say_hello everybody! Hello everybody!
Unlike other shells, fish does not have aliases or special prompt syntax. Functions take their place. 2
You can list the names of all functions with the functions builtin (note the plural!). fish starts out with a number of functions:
> functions N_, abbr, alias, bg, cd, cdh, contains_seq, delete-or-exit, dirh, dirs, disown, down-or-search, edit_command_buffer, export, fg, fish_add_path, fish_breakpoint_prompt, fish_clipboard_copy, fish_clipboard_paste, fish_config, fish_default_key_bindings, fish_default_mode_prompt, fish_git_prompt, fish_hg_prompt, fish_hybrid_key_bindings, fish_indent, fish_is_root_user, fish_job_summary, fish_key_reader, fish_md5, fish_mode_prompt, fish_npm_helper, fish_opt, fish_print_git_action, fish_print_hg_root, fish_prompt, fish_sigtrap_handler, fish_svn_prompt, fish_title, fish_update_completions, fish_vcs_prompt, fish_vi_cursor, fish_vi_key_bindings, funced, funcsave, grep, help, history, hostname, isatty, kill, la, ll, ls, man, nextd, nextd-or-forward-word, open, popd, prevd, prevd-or-backward-word, prompt_hostname, prompt_pwd, psub, pushd, realpath, seq, setenv, suspend, trap, type, umask, up-or-search, vared, wait
You can see the source for any function by passing its name to
> functions ls function ls --description 'List contents of directory' command ls -G $argv end
> while true echo "Loop forever" end Loop forever Loop forever Loop forever ... # yes, this really will loop forever. Unless you abort it with ctrl-c.
For loops can be used to iterate over a list. For example, a list of files:
> for file in *.txt cp $file $file.bak end
Iterating over a list of numbers can be done with
> for x in (seq 5) touch file_$x.txt end
Unlike other shells, there is no prompt variable like
PS1. To display your prompt, fish executes the fish_prompt function and uses its output as the prompt. And if it exists, fish also executes the fish_right_prompt function and uses its output as the right prompt.
You can define your own prompt from the command line:
> function fish_prompt; echo "New Prompt % "; end New Prompt % _
Then, if you are happy with it, you can save it to disk by typing
funcsave fish_prompt. This saves the prompt in
~/.config/fish/functions/fish_prompt.fish. (Or, if you want, you can create that file manually from the start.)
Multiple lines are OK. Colors can be set via set_color, passing it named ANSI colors, or hex RGB values:
function fish_prompt set_color purple date "+%m/%d/%y" set_color F00 echo (pwd) '>' (set_color normal) end
This prompt would look like:
02/06/13 /home/tutorial > _
You can choose among some sample prompts by running
$PATH is an environment variable containing the directories that fish searches for commands. Unlike other shells, $PATH is a list, not a colon-delimited string.
Fish takes care to set
$PATH to a default, but typically it is just inherited from fish's parent process and is set to a value that makes sense for the system - see Exports.
To prepend /usr/local/bin and /usr/sbin to
$PATH, you can write:
> set PATH /usr/local/bin /usr/sbin $PATH
To remove /usr/local/bin from
$PATH, you can write:
> set PATH (string match -v /usr/local/bin $PATH)
For compatibility with other shells and external commands, $PATH is a path variable, and so will be joined with colons (not spaces) when you quote it:
> echo "$PATH" /usr/local/sbin:/usr/local/bin:/usr/bin
and it will be exported like that, and when fish starts it splits the $PATH it receives into a list on colon.
You can do so directly in
config.fish, like you might do in other shells with
.profile. See this example.
A faster way is to use the fish_add_path function, which adds given directories to the path if they aren't already included. It does this by modifying the
$fish_user_paths universal variable, which is automatically prepended to
$PATH. For example, to permanently add
/usr/local/bin to your
$PATH, you could write:
> fish_add_path /usr/local/bin
The advantage is that you don't have to go mucking around in files: just run this once at the command line, and it will affect the current session and all future instances too. You can also add this line to config.fish, as it only adds the component if necessary.
Or you can modify $fish_user_paths yourself, but you should be careful not to append to it unconditionally in config.fish, or it will grow longer and longer.
Startup (Where's .bashrc?)¶
Fish starts by executing commands in
~/.config/fish/config.fish. You can create it if it does not exist.
It is possible to directly create functions and variables in
config.fish file, using the commands shown above. For example:
> cat ~/.config/fish/config.fish set -x PATH $PATH /sbin/ function ll ls -lh $argv end
However, it is more common and efficient to use autoloading functions and universal variables.
If you want to organize your configuration, fish also reads commands in .fish files in
~/.config/fish/conf.d/. See initialization for the details.
When fish encounters a command, it attempts to autoload a function for that command, by looking for a file with the name of that command in
For example, if you wanted to have a function
ll, you would add a text file
> cat ~/.config/fish/functions/ll.fish function ll ls -lh $argv end
This is the preferred way to define your prompt as well:
> cat ~/.config/fish/functions/fish_prompt.fish function fish_prompt echo (pwd) "> " end
A universal variable is a variable whose value is shared across all instances of fish, now and in the future – even after a reboot. You can make a variable universal with
> set -U EDITOR vim
Now in another shell:
> echo $EDITOR vim
Switching to fish?¶
If you wish to use fish (or any other shell) as your default shell, you need to enter your new shell's executable in two places.
Add the shell to
> echo /usr/local/bin/fish | sudo tee -a /etc/shells
Change your default shell with:
> chsh -s /usr/local/bin/fish
This assumes you installed fish to /usr/local/bin, which is the default location when you've compiled it yourself. If you installed it with a package manager, the usual location is /usr/bin/fish, but package managers typically already add it to /etc/shells. Just substitute the correct location.
(To change it back to another shell, just substitute
/bin/zsh as appropriate in the steps above.)