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!
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.
When you start fish, you should see this:
Welcome to fish, the friendly interactive shell Type help for instructions on how to use fish you@hostname ~>
fish comes with a default prompt that shows your username, hostname, and working directory. You'll see how to change your prompt further down. From now on, we'll pretend your prompt is just a '>' to save space.
fish runs commands like other shells: you type a command, followed by its arguments. Spaces are separators:
> echo hello world hello worldYou 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 FileCommands can be chained with semicolons.
> man set set - handle environment variables Synopsis...
> /bin/mkdA 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:
> /bin/mkdirfish will underline valid file paths 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 variables directly.
> 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.
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 < and >. Unlike other shells, stderr is redirected with a caret ^
> grep fish < /etc/shells > ~/output.txt ^ ~/errors.txt
> /bin/hostnameIt knows about paths and options:
> grep --ignore-caseAnd 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/dooTo accept the autosuggestion, hit right arrow or Control-F. If the autosuggestion is not what you want, just ignore it.
fish comes with a rich set of tab completions, that work "out of the box."
Press tab, and fish will attempt to complete the command, argument, or path:
If there's more than one possibility, it will list them:
> ~/stuff/s~/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 prTry hitting tab and see what fish can do! git merge prompt_designer > git checkout b builtin_list_io_merge (Branch) builtin_set_color (Branch) busted_events (Tag)
Like other shells, a dollar sign performs variable substitution:
> echo My home directory is $HOME My home directory is /home/tutorialVariable substitution also occurs 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 $PWDUnlike other shells, fish has no dedicated 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, Mister and 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 NoodleIn 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.
> false > echo $status 1Zero is considered success, and non-zero is failure.
> set -x MyVariable SomeValue > env | grep MyVariable MyVariable=SomeValueYou can erase a variable with -e or --erase
> set -e MyVariable > env | grep MyVariable
The 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
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:
> count $PATH 5You 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/binYou 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/binYou 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 /binYou 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
> echo In (pwd), running (uname) In /home/tutorial, running FreeBSDA common idiom is to capture the output of a command in a variable:
> set os (uname) > echo $os LinuxCommand 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
> cp file1.txt file1_bak.txt; and echo "Backup successful"; or echo "Backup failed" Backup failed
if grep fish /etc/shells echo Found fish else if grep bash /etc/shells echo Found bash else echo Got nothing endThere 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! endNote that case does not fall through, and can accept multiple arguments or (quoted) wildcards.
> 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.
You can list the names of all functions with the functions keyword (note the plural!). fish starts out with a number of functions:
> functions alias, cd, delete-or-exit, dirh, dirs, down-or-search, eval, export, fish_command_not_found_setup, fish_config, fish_default_key_bindings, fish_prompt, fish_right_prompt, fish_sigtrap_handler, fish_update_completions, funced, funcsave, grep, help, history, isatty, ls, man, math, nextd, nextd-or-forward-word, open, popd, prevd, prevd-or-backward-word, prompt_pwd, psub, pushd, seq, setenv, sgrep, trap, type, umask, up-or-search, vared
You can see the source for any function by passing its name to functions:
> 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 ...For loops can be used to iterate over a list. For example, a list of files:
> for file in *.txt cp $file $file.bak endIterating over a list of numbers can be done with `seq`:
> for x in (seq 5) touch file_$x.txt end
> function fish_prompt echo "New Prompt % " end New Prompt %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 FF0 echo (pwd) '>' set_color normal end 02/06/13 /home/tutorial >
You can choose among some sample prompts by running fish_config prompt. fish also supports RPROMPT through fish_right_prompt.
> set -U fish_user_paths $fish_user_paths /usr/local/bin
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.
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 ~/.config/fish/functions/.
For example, if you wanted to have a function ll, you would add a text file ll.fish to ~/.config/fish/functions:
> cat ~/.config/fish/functions/ll.fish function ll ls -lh $argv endThis 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:
> set -U EDITOR vimNow in another shell:
> echo $EDITOR vim