fish-shell/doc_src/tutorial.hdr

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\page tutorial Tutorial
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- <a href="#tut_why_fish">Why fish?</a>
- <a href="#tut_learning_Fish">Learning fish</a>
- <a href="#tut_running_commands">Running Commands</a>
- <a href="#tut_getting_help">Getting Help</a>
- <a href="#tut_syntax_highlighting">Syntax Highlighting</a>
- <a href="#tut_wildcards">Wildcards</a>
- <a href="#tut_pipes_and_redirections">Pipes and Redirections</a>
- <a href="#tut_autosuggestions">Autosuggestions</a>
- <a href="#tut_tab_completions">Tab Completions</a>
- <a href="#tut_variables">Variables</a>
- <a href="#tut_exit_status">Exit Status</a>
- <a href="#tut_exports">Shell Variables</a>
- <a href="#tut_lists">Lists</a>
- <a href="#tut_command_substitutions">Command Substitutions</a>
- <a href="#tut_combiners">Combiners (And, Or, Not)</a>
- <a href="#tut_conditionals">Conditionals (If, Else, Switch)</a>
- <a href="#tut_functions">Functions</a>
- <a href="#tut_loops">Loops</a>
- <a href="#tut_prompt">Prompt</a>
- <a href="#tut_path">$PATH</a>
- <a href="#tut_startup">Startup</a>
- <a href="#tut_autoload">Autoloading Functions</a>
- <a href="#tut_more">Ready for more?</a>

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<div class="tutorial fish_right_bar">
<h1 class="interior_title">fish tutorial</h1>
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\section tut_why_fish Why fish?

`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!


\section tut_learning_Fish Learning fish

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 <em>unlike other shells</em>, which is used to call out important differences.

When you start `fish`, you should see this:

\fish{cli-dark}
<outp>Welcome to fish, the friendly interactive shell</outp>
<outp>Type <span class="cwd">help</span> for instructions on how to use fish</outp>
<asis>you@hostname</asis> ~>____
\endfish

`fish` comes with a default prompt that shows your username, hostname, and working directory. You'll see <a href="#tut_prompt">how to change your prompt</a> further down. From now on, we'll pretend your prompt is just a '`>`' to save space.


\section tut_running_commands Running Commands

`fish` runs commands like other shells: you type a command, followed by its arguments. Spaces are separators:

\fish{cli-dark}
>_ echo hello world
<outp>hello world</outp>
\endfish

You can include a literal space in an argument with a backslash, or by using single or double quotes:

\fish{cli-dark}
>_ mkdir My\ Files
>_ cp ~/Some\ File 'My Files'
>_ ls "My Files"
<outp>Some File</outp>
\endfish

Commands can be chained with semicolons.


\section tut_getting_help Getting Help

`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.

\fish{cli-dark}
>_ man set
<outp>set - handle shell variables</outp>
<outp>  Synopsis...</outp>
\endfish


\section tut_syntax_highlighting Syntax Highlighting

You'll quickly notice that `fish` performs syntax highlighting as you type. Invalid commands are colored red by default:

\fish{cli-dark}
>_ <error>/bin/mkd</error>
\endfish

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:

\fish{cli-dark}
>_ /bin/mkdir
\endfish

`fish` will underline valid file paths as you type them:

\fish{cli-dark}
>_ cat <u>~/somefi</u>___
\endfish

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.


\section tut_wildcards Wildcards

`fish` supports the familiar wildcard `*`. To list all JPEG files:

\fish{cli-dark}
>_ ls *.jpg
<outp>lena.jpg</outp>
<outp>meena.jpg</outp>
<outp>santa maria.jpg</outp>
\endfish

You can include multiple wildcards:

\fish{cli-dark}
>_ ls l*.p*
<outp>lena.png</outp>
<outp>lesson.pdf</outp>
\endfish

Especially powerful is the recursive wildcard ** which searches directories recursively:

\fish{cli-dark}
>_ ls /var/**.log
<outp>/var/log/system.log</outp>
<outp>/var/run/sntp.log</outp>
\endfish

If that directory traversal is taking a long time, you can @key{Control,C} out of it.


\section tut_pipes_and_redirections Pipes and Redirections

You can pipe between commands with the usual vertical bar:

\fish{cli-dark}
>_ echo hello world | wc
<outp>       1       2      12</outp>
\endfish

stdin and stdout can be redirected via the familiar &lt; and &gt;. Unlike other shells, stderr is redirected with a caret ^

\fish{cli-dark}
>_ grep fish < /etc/shells > ~/output.txt ^ ~/errors.txt
\endfish


\section tut_autosuggestions Autosuggestions

`fish` suggests commands as you type, and shows the suggestion to the right of the cursor, in gray. For example:

\fish{cli-dark}
>_ <error>/bin/h</error><s>___ostname</s>
\endfish

It knows about paths and options:

\fish{cli-dark}
>_ grep --i<s>___gnore-case</s>
\endfish

And history too. Type a command once, and you can re-summon it by just typing a few letters:

\fish{cli-dark}
>_ <error>r</error><s>___sync -avze ssh . myname@somelonghost.com:/some/long/path/doo/dee/doo/dee/doo</s>
\endfish

To accept the autosuggestion, hit @cursor_key{&rarr;,right arrow} or @key{Control,F}. To accept a single word of the autosuggestion, @key{Alt,&rarr;} (right arrow). If the autosuggestion is not what you want, just ignore it.

\section tut_tab_completions Tab Completions

`fish` comes with a rich set of tab completions, that work "out of the box."

Press @key{Tab}, and `fish` will attempt to complete the command, argument, or path:

\fish{cli-dark}
>_ <error>/pri</error> @key{Tab} &rarr; /private/
\endfish

If there's more than one possibility, it will list them:

\fish{cli-dark}
>_ <error>~/stuff/s</error> @key{Tab}
<outp><m>~/stuff/s</m>cript.sh  <i>(Executable, 4.8kB)</i>  <m>~/stuff/s</m>ources/  <i>(Directory)</i></outp>
\endfish

Hit tab again to cycle through the possibilities.

`fish` can also complete many commands, like git branches:

\fish{cli-dark}
>_ git merge pr @key{Tab} &rarr; git merge prompt_designer
>_ git checkout b @key{Tab}
<outp><m>b</m>uiltin_list_io_merge <i>(Branch)</i> <m>b</m>uiltin_set_color <i>(Branch)</i> <m>b</m>usted_events <i>(Tag)</i></outp>
\endfish

Try hitting tab and see what `fish` can do!

\section tut_variables Variables

Like other shells, a dollar sign performs variable substitution:

\fish{cli-dark}
>_ echo My home directory is $HOME
<outp>My home directory is /home/tutorial</outp>
\endfish

Variable substitution also occurs in double quotes, but not single quotes:

\fish{cli-dark}
>_ echo "My current directory is $PWD"
<outp>My current directory is /home/tutorial</outp>
>_ echo 'My current directory is $PWD'
<outp>My current directory is $PWD</outp>
\endfish

Unlike 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.

\fish{cli-dark}
>_ set name 'Mister Noodle'
>_ echo $name
<outp>Mister Noodle</outp>
\endfish

(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:

\fish{cli-dark}
>_ mkdir $name
>_ ls
<outp>Mister Noodle</outp>
\endfish

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.


\section tut_exit_status Exit Status

Unlike other shells, `fish` stores the exit status of the last command in `$status` instead of `$?`.

\fish{cli-dark}
>_ false
>_ echo $status
<outp>1</outp>
\endfish

Zero is considered success, and non-zero is failure.


\section tut_exports Exports (Shell Variables)

Unlike other shells, `fish` does not have an export command. Instead, a variable is exported via an option to `set`, either `--export` or just `-x`.

\fish{cli-dark}
>_ set -x MyVariable SomeValue
>_ env | grep MyVariable
<outp><sm>MyVariable</sm>=SomeValue</outp>
\endfish

You can erase a variable with `-e` or `--erase`

\fish{cli-dark}
>_ set -e MyVariable
>_ env | grep MyVariable
<outp>(no output)</outp>
\endfish


\section tut_lists Lists

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:

\fish{cli-dark}
>_ echo $PATH
<outp>/usr/bin /bin /usr/sbin /sbin /usr/local/bin</outp>
\endfish

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`:

\fish{cli-dark}
>_ count $PATH
<outp>5</outp>
\endfish

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:

\fish{cli-dark}
>_ set PATH $PATH /usr/local/bin
\endfish


You can access individual elements with square brackets. Indexing starts at 1 from the beginning, and -1 from the end:

\fish{cli-dark}
>_ echo $PATH
<outp>/usr/bin /bin /usr/sbin /sbin /usr/local/bin</outp>
>_ echo $PATH[1]
<outp>/usr/bin</outp>
>_ echo $PATH[-1]
<outp>/usr/local/bin</outp>
\endfish

You can also access ranges of elements, known as "slices:"

\fish{cli-dark}
>_ echo $PATH[1..2]
<outp>/usr/bin /bin</outp>
>_ echo $PATH[-1..2]
<outp>/usr/local/bin /sbin /usr/sbin /bin</outp>
\endfish

You can iterate over a list (or a slice) with a for loop:

\fish{cli-dark}
>_ for val in $PATH
    echo "entry: $val"
  end
<outp>entry: /usr/bin/</outp>
<outp>entry: /bin</outp>
<outp>entry: /usr/sbin</outp>
<outp>entry: /sbin</outp>
<outp>entry: /usr/local/bin</outp>
\endfish

Lists adjacent to other lists or strings are expanded as cartesian products unless quoted (see <a href="index.html#expand-variable">Variable expansion</a>):

\fish{cli-dark}
>_ set -l a 1 2 3
>_ set -l 1 a b c
>_ echo $a$1
<outp>1a 2a 3a 1b 2b 3b 1c 2c 3c</outp>
>_ echo $a" banana"
<outp>1 banana 2 banana 3 banana</outp>
>_ echo "$a banana"
<outp>1 2 3 banana</outp>
\endfish

This is similar to <a href="index.html#expand-brace">Brace expansion</a>.

\section tut_command_substitutions Command Substitutions

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:

\fish{cli-dark}
>_ echo In (pwd), running (uname)
<outp>In /home/tutorial, running FreeBSD</outp>
\endfish

A common idiom is to capture the output of a command in a variable:

\fish{cli-dark}
>_ set os (uname)
>_ echo $os
<outp>Linux</outp>
\endfish

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:

\fish{cli-dark}
>_ touch <i class="quote">"testing_"</i>(date +%s)<i class="quote">".txt"</i>
>_ ls *.txt
<outp>testing_1360099791.txt</outp>
\endfish


\section tut_combiners Combiners (And, Or, Not)

Unlike other shells, `fish` does not have special syntax like &amp;&amp; or || to combine commands. Instead it has commands `and`, `or`, and `not`.

\fish{cli-dark}
>_ cp file1.txt file1_bak.txt; and echo "Backup successful"; or echo "Backup failed"
<outp>Backup failed</outp>
\endfish


\section tut_conditionals Conditionals (If, Else, Switch)

Use `if`, `else if`, and `else` to conditionally execute code, based on the exit status of a command.

\fish{cli-dark}
if grep fish /etc/shells
    echo Found fish
else if grep bash /etc/shells
    echo Found bash
else
    echo Got nothing
end
\endfish

There is also a `switch` command:

\fish{cli-dark}
switch (uname)
case Linux
    echo Hi Tux!
case Darwin
    echo Hi Hexley!
case FreeBSD NetBSD DragonFly
    echo Hi Beastie!
case '*'
    echo Hi, stranger!
end
\endfish

Note that `case` does not fall through, and can accept multiple arguments or (quoted) wildcards.


\section tut_functions Functions

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:

\fish{cli-dark}
>_ function say_hello
     echo Hello $argv
  end
>_ say_hello
<outp>Hello</outp>
>_ say_hello everybody!
<outp>Hello everybody!</outp>
\endfish

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:

\fish{cli-dark}
>_ functions
<outp>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, trap, type, umask, up-or-search, vared</outp>
\endfish

You can see the source for any function by passing its name to `functions`:

\fish{cli-dark}
>_ functions ls
function ls --description 'List contents of directory'
    command ls -G $argv
end
\endfish


\section tut_loops Loops

While loops:

\fish{cli-dark}
>_ while true
    echo <i class="quote">"Loop forever"</i>
end
<outp>Loop forever</outp>
<outp>Loop forever</outp>
<outp>Loop forever</outp>
<outp>...</outp>
\endfish

For loops can be used to iterate over a list. For example, a list of files:

\fish{cli-dark}
>_ for file in *.txt
    cp $file $file.bak
end
\endfish

Iterating over a list of numbers can be done with `seq`:

\fish{cli-dark}
>_ for x in (seq 5)
    touch file_$x.txt
end
\endfish


\section tut_prompt Prompt

Unlike other shells, there is no prompt variable like PS1. To display your prompt, `fish` executes a function with the name `fish_prompt`, and its output is used as the prompt.

You can define your own prompt:

\fish{cli-dark}
>_ function fish_prompt
    echo "New Prompt % "
end
<asis>New Prompt % </asis>___
\endfish

Multiple lines are OK. Colors can be set via `set_color`, passing it named ANSI colors, or hex RGB values:

\fish{cli-dark}
>_ function fish_prompt
      set_color purple
      date "+%m/%d/%y"
      set_color FF0
      echo (pwd) '>'
      set_color normal
  end
<span style="color: purple">02/06/13</span>
<span style="color: #FF0">/home/tutorial ></span>___
\endfish

You can choose among some sample prompts by running `fish_config prompt`. `fish` also supports RPROMPT through `fish_right_prompt`.

\section tut_path $PATH

`$PATH` is an environment variable containing the directories in which `fish` searches for commands. Unlike other shells, $PATH is a [list](#tut_lists), not a colon-delimited string.

To prepend to `$PATH`, you can write:

\fish{cli-dark}
>_ set PATH /new/path $PATH
\endfish

You can do so directly in `fish.config`, like you might do in other shells with `.profile`. See [this example](#path_example).

A faster way is to modify the `$fish_user_paths` [universal variable](#tut_universal), which is automatically prepended to `$PATH`. For example, to permanently add `/usr/local/bin` to your `$PATH`, you could write:

\fish{cli-dark}
>_ set -U fish_user_paths /usr/local/bin $fish_user_paths
\endfish

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. (Note: you should NOT add this line to `fish.config`. If you do, the variable will get longer each time you run fish!)

\section tut_startup 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:

<a name="path_example"></a>
\fish{cli-dark}
>_ cat ~/.config/fish/config.fish

set -x PATH $PATH /sbin/

function ll
    ls -lh $argv
end
\endfish

However, it is more common and efficient to use  autoloading functions and universal variables.

\section tut_autoload Autoloading Functions

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`:

\fish{cli-dark}
>_ cat ~/.config/fish/functions/ll.fish
function ll
    ls -lh $argv
end
\endfish

This is the preferred way to define your prompt as well:

\fish{cli-dark}
>_ cat ~/.config/fish/functions/fish_prompt.fish
function fish_prompt
    echo (pwd) "> "
end
\endfish

See the documentation for <a href="commands.html#funced">funced</a> and <a href="commands.html#funcsave">funcsave</a> for ways to create these files automatically.

\section tut_universal Universal Variables

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`:

\fish{cli-dark}
>_ set -U EDITOR vim
\endfish

Now in another shell:

\fish{cli-dark}
>_ echo $EDITOR
vim
\endfish

\section tut_more  Ready for more?

If you want to learn more about fish, there is <a href="index.html">lots of detailed documentation</a>, an <a href="https://lists.sourceforge.net/lists/listinfo/fish-users">official mailing list</a>, the IRC channel \#fish on `irc.oftc.net`, and the <a href="https://github.com/fish-shell/fish-shell/">github page</a>.

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