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Commands

# Command reference

`fish` ships with a large number of builtin commands, shellscript functions and external commands. These are all described below.

Almost all fish commands respond to the `-h` or `--help` options to display their relevant help, also accessible using the `help` and `man` commands, like so:

    echo -h
    echo --help
    # Prints help to the terminal window

    man echo
    # Displays the man page in the system pager
    # (normally 'less', 'more' or 'most').

    help echo
    # Open a web browser to show the relevant documentation

# abbr - manage fish abbreviations

## Synopsis

    abbr --add word phrase...
    abbr --rename word new_word
    abbr --show
    abbr --list
    abbr --erase word

## Description

`abbr` manipulates the list of abbreviations that fish will expand.

Abbreviations are user-defined character sequences or words that are replaced with longer phrases after they are entered. For example, a frequently-run command such as `git checkout` can be abbreviated to `gco`. After entering `gco` and pressing Space or Enter, the full text `git checkout` will appear in the command line.

Abbreviations are stored in a variable named `fish_user_abbreviations`. This is automatically created as a universal variable the first time an abbreviation is created. If you want your abbreviations to be private to a particular fish session you can put the following in your *~/.config/fish/config.fish* file before you define your first abbrevation:

    if status --is-interactive
        set -g fish_user_abbreviations
        abbr --add first 'echo my first abbreviation'
        abbr --add second 'echo my second abbreviation'
        # etcetera
    end

You can create abbreviations directly on the command line and they will be saved automatically and made visible to other fish sessions if `fish_user_abbreviations` is a universal variable. If you keep the variable as universal, `abbr --add` statements in config.fish will do nothing but slow down startup slightly.

## Options

The following parameters are available:

- `-a WORD PHRASE` or `--add WORD PHRASE` Adds a new abbreviation, causing WORD to be expanded to PHRASE.
- `-r WORD NEW_WORD` or `--rename WORD NEW_WORD` Renames an abbreviation, from WORD to NEW_WORD.
- `-s` or `--show` Show all abbreviated words and their expanded phrases in a manner suitable for export and import.
- `-l` or `--list` Lists all abbreviated words.
- `-e WORD` or `--erase WORD` Erase the abbreviation WORD.

Note: fish version 2.1 supported `-a WORD=PHRASE`. This syntax is now deprecated but will still be converted.

## Examples

    abbr -a gco git checkout

Add a new abbreviation where `gco` will be replaced with `git checkout`.

    abbr -r gco gch

Renames an existing abbreviation from `gco` to `gch`.

    abbr -e gco

Erase the `gco` abbreviation.

    ssh another_host abbr -s | source

Import the abbreviations defined on another_host over SSH.

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# alias - create a function

## Synopsis

    alias
    alias NAME DEFINITION
    alias NAME=DEFINITION

## Description

`alias` is a simple wrapper for the `function` builtin, which creates a function wrapping a command. It has similar syntax to POSIX shell `alias`. For other uses, it is recommended to define a function.

`fish` marks functions that have been created by `alias` by including the command used to create them in the function description. You can list `alias`-created functions by running `alias` without arguments. They must be erased using `functions -e`.

- `NAME` is the name of the alias
- `DEFINITION` is the actual command to execute. The string `$argv` will be appended.

You cannot create an alias to a function with the same name. Note that spaces need to be escaped in the call to `alias` just like at the command line, even inside quoted parts.

## Example

The following code will create `rmi`, which runs `rm` with additional arguments on every invocation.

    alias rmi="rm -i"

    # This is equivalent to entering the following function:
    function rmi --wraps rm --description 'alias rmi=rm -i'
        rm -i $argv
    end

    # This needs to have the spaces escaped or "Chrome.app..." will be seen as an argument to "/Applications/Google":
    alias chrome='/Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome banana'

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# and - conditionally execute a command

## Synopsis

    COMMAND1; and COMMAND2

## Description

`and` is used to execute a command if the current exit status (as set by the previous command) is 0.

`and` statements may be used as part of the condition in an `if` or `while` block. See the documentation for `if` and `while` for examples.

`and` does not change the current exit status itself, but the command it runs most likely will. The exit status of the last foreground command to exit can always be accessed using the $status variable.

## Example

The following code runs the `make` command to build a program. If the build succeeds, `make`'s exit status is 0, and the program is installed. If either step fails, the exit status is 1, and `make clean` is run, which removes the files created by the build process.

    make; and make install; or make clean

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# argparse - parse options passed to a fish script or function

## Synopsis

    argparse [OPTIONS] OPTION_SPEC... -- [ARG...]

## Description

This command makes it easy for fish scripts and functions to handle arguments in a manner 100% identical to how fish builtin commands handle their arguments. You pass a sequence of arguments that define the options recognized, followed by a literal `--`, then the arguments to be parsed (which might also include a literal `--`). More on this in the usage section below.

Each OPTION_SPEC can be written in the domain specific language described below or created using the companion `fish_opt` command. All OPTION_SPECs must appear after any argparse flags and before the `--` that separates them from the arguments to be parsed.

Each option that is seen in the ARG list will result in a var name of the form `_flag_X`, where `X` is the short flag letter and the long flag name. The OPTION_SPEC always requires a short flag even if it can't be used. So there will always be `_flag_X` var set using the short flag letter if the corresponding short or long flag is seen. The long flag name var (e.g., `_flag_help`) will only be defined, obviously, if the OPTION_SPEC includes a long flag name.

For example `_flag_h` and `_flag_help` if `-h` or `--help` is seen. The var will be set with local scope (i.e., as if the script had done `set -l _flag_X`). If the flag is a boolean (that is, does not have an associated value) the values are the short and long flags seen. If the option is not a boolean flag the values will be zero or more values corresponding to the values collected when the ARG list is processed. If the flag was not seen the flag var will not be set.

The following `argparse` options are available. They must appear before all OPTION_SPECs:

- `-n` or `--name` is the command name to insert into any error messages. If you don't provide this value `argparse` will be used.
- `-x` or `--exclusive` should be followed by a comma separated list of short of long options that are mutually exclusive. You can use this option more than once to define multiple sets of mutually exclusive options.
- `-N` or `--min-args` is followed by an integer that defines the minimum number of acceptable non-option arguments. The default is zero.
- `-X` or `--max-args` is followed by an integer that defines the maximum number of acceptable non-option arguments. The default is infinity.
- `-s` or `--stop-nonopt` causes scanning the arguments to stop as soon as the first non-option argument is seen. Using this arg is equivalent to calling the C function `getopt_long()` with the short options starting with a `+` symbol. This is sometimes known as "POSIXLY CORRECT". If this flag is not used then arguments are reordered (i.e., permuted) so that all non-option arguments are moved after option arguments. This mode has several uses but the main one is to implement a command that has subcommands.
- `-h` or `--help` displays help about using this command.

## Usage

Using this command involves passing two sets of arguments separated by `--`. The first set consists of one or more option specifications (`OPTION_SPEC` above) and options that modify the behavior of `argparse`. These must be listed before the `--` argument. The second set are the arguments to be parsed in accordance with the option specifications. They occur after the `--` argument and can be empty. More about this below but here is a simple example that might be used in a function named `my_function`:

    argparse --name=my_function 'h/help' 'n/name:' -- $argv
    or return

If `$argv` is empty then there is nothing to parse and `argparse` returns zero to indicate success. If `$argv` is not empty then it is checked for flags `-h`, `--help`, `-n` and `--name`. If they are found they are removed from the arguments and local variables (more on this below) are set so the script can determine which options were seen. Assuming `$argv` doesn't have any errors, such as a missing mandatory value for an option, then `argparse` exits with status zero. Otherwise it writes appropriate error messages to stderr and exits with a status of one.

Not including a `--` argument is an error condition. You do not have to include any arguments after the `--` but you must include the `--`. For example, this is acceptable:

    set -l argv
    argparse 'h/help' 'n/name' -- $argv

But this is not:

    set -l argv
    argparse 'h/help' 'n/name' $argv

The first `--` seen is what allows the `argparse` command to reliably seperate the option specifications from the command arguments.

## Option Specifications

Each option specification is a string composed of

- A short flag letter (which is mandatory). It must be an alphanumeric or "#". The "#" character is special and means that a flag of the form `-123` is valid. The short flag "#" must be followed by "-" (since the short name isn't otherwise valid since `_flag_#` is not a valid var name) and must but followed by a long flag name with no modifiers.
- A `/` if the short flag can be used by someone invoking your command else `-` if it should not be exposed as a valid short flag. If there is no long flag name these characters should be omitted. You can also specify a '#' to indicate the short and long flag names can be used and the value can be specified as an implicit int; i.e., a flag of the form `-NNN`.
- A long flag name which is optional. If not present then only the short flag letter can be used.
- Nothing if the flag is a boolean that takes no argument or is an implicit int flag, else
- `=` if it requires a value and only the last instance of the flag is saved, else
- `=?` it takes an optional value and only the last instance of the flag is saved, else
- `=+` if it requires a value each instance of the flag is saved.
- Optionally a `!` followed by fish script to validate the value. Typically this will be a function to run. If the return status is zero the value for the flag is valid. If non-zero the value is invalid. Any error messages should be written to stdout (not stderr). See the section on Flag Value Validation for more information.

See the `fish_opt` command for a friendlier but more verbose way to create option specifications.

In the following examples if a flag is not seen when parsing the arguments then the corresponding _flag_X var(s) will not be set.

## Flag Value Validation

It is common to want to validate the the value provided for an option satisfies some criteria. For example, that it is a valid integer within a specific range. You can always do this after `argparse` returns but you can also request that `argparse` perform the validation by executing arbitrary fish script. To do so simply append an `!` (exclamation-mark) then the fish script to be run. When that code is executed three vars will be defined:

- `_argparse_cmd` will be set to the value of the value of the `argparse --name` value.
- `_flag_name` will be set to the short or long flag that being processed.
- `_flag_value` will be set to the value associated with the flag being processed.

If you do this via a function it should be defined with the `--no-scope-shadowing` flag. Otherwise it won't have access to those variables.

The script should write any error messages to stdout, not stderr. It should return a status of zero if the flag value is valid otherwise a non-zero status to indicate it is invalid.

Fish ships with a `_validate_int` function that accepts a `--min` and `--max` flag. Let's say your command accepts a `-m` or `--max` flag and the minimum allowable value is zero and the maximum is 5. You would define the option like this: `m/max=!_validate_int --min 0 --max 5`. The default if you just call `_validate_int` without those flags is to simply check that the value is a valid integer with no limits on the min or max value allowed.

## Example OPTION_SPECs

Some OPTION_SPEC examples:

- `h/help` means that both `-h` and `--help` are valid. The flag is a boolean and can be used more than once. If either flag is used then `_flag_h` and `_flag_help` will be set to the count of how many times either flag was seen.
- `h-help` means that only `--help` is valid. The flag is a boolean and can be used more than once. If the long flag is used then `_flag_h` and `_flag_help` will be set to the count of how many times the long flag was seen.
- `n/name=` means that both `-n` and `--name` are valid. It requires a value and can be used at most once. If the flag is seen then `_flag_n` and `_flag_name` will be set with the single mandatory value associated with the flag.
- `n/name=?` means that both `-n` and `--name` are valid. It accepts an optional value and can be used at most once. If the flag is seen then `_flag_n` and `_flag_name` will be set with the value associated with the flag if one was provided else it will be set with no values.
- `n-name=+` means that only `--name` is valid. It requires a value and can be used more than once. If the flag is seen then `_flag_n` and `_flag_name` will be set with the values associated with each occurrence of the flag.
- `x` means that only `-x` is valid. It is a boolean can can be used more than once. If it is seen then `_flag_x` will be set to the count of how many times the flag was seen.
- `x=`, `x=?`, and `x=+` are similar to the n/name examples above but there is no long flag alternative to the short flag `-x`.
- `x-` is not valid since there is no long flag name and therefore the short flag, `-x`, has to be usable. This is obviously true whether or not the specification also includes one of `:`, `::`, `+`.
- `#-max` means that flags matching the regex "^--?\d+$" are valid. When seen they are assigned to the variable `_flag_max`. This allows any valid positive or negative integer to be specified by prefixing it with a single "-". Many commands support this idiom. For example `head -3 /a/file` to emit only the first three lines of /a/file.
- `n::max` means that flags matching the regex "^--?\d+$" are valid. When seen they are assigned to the variables `_flag_n` and `_flag_max`. This allows any valid positive or negative integer to be specified by prefixing it with a single "-". Many commands support this idiom. For example `head -3 /a/file` to emit only the first three lines of /a/file. You can also specify the value using either flag: `-n NNN` or `--max NNN` in this example.

After parsing the arguments the `argv` var is set with local scope to any values not already consumed during flag processing. If there are not unbound values the var is set but `count $argv` will be zero.

If an error occurs during argparse processing it will exit with a non-zero status and appropriate error messages are written to stderr.

## Notes

Prior to the addition of this builtin command in the 2.7.0 release there were two main ways to parse the arguments passed to a fish script or function. One way was to use the OS provided `getopt` command. The problem with that is that the GNU and BSD implementations are not compatible. Which makes using that external command difficult other than in trivial situations. The other way is to iterate over `$argv` and use the fish `switch` statement to decide how to handle the argument. That, however, involves a huge amount of boilerplate code. It is also borderline impossible to implement the same behavior as builtin commands.

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# begin - start a new block of code

## Synopsis

    begin; [COMMANDS...;] end

## Description

`begin` is used to create a new block of code.

The block is unconditionally executed. `begin; ...; end` is equivalent to `if true; ...; end`.

`begin` is used to group a number of commands into a block. This allows the introduction of a new variable scope, redirection of the input or output of a set of commands as a group, or to specify precedence when using the conditional commands like `and`.

`begin` does not change the current exit status itself. After the block has completed, `$status` will be set to the status returned by the most recent command.

## Example

The following code sets a number of variables inside of a block scope. Since the variables are set inside the block and have local scope, they will be automatically deleted when the block ends.

    begin
        set -l PIRATE Yarrr
        ...
    end

    echo $PIRATE
    # This will not output anything, since the PIRATE variable
    # went out of scope at the end of the block

In the following code, all output is redirected to the file out.html.

    begin
        echo $xml_header
        echo $html_header
        if test -e $file
            ...
        end
        ...
    end > out.html

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# bg - send jobs to background

## Synopsis

    bg [PID...]

## Description

`bg` sends jobs to the background, resuming them if they are stopped. A background job is executed simultaneously with fish, and does not have access to the keyboard. If no job is specified, the last job to be used is put in the background. If PID is specified, the jobs with the specified process group IDs are put in the background.

The PID of the desired process is usually found by using process expansion.

When at least one of the arguments isn't a valid job specifier (i.e. PID), `bg` will print an error without backgrounding anything.

When all arguments are valid job specifiers, bg will background all matching jobs that exist.

## Example

`bg %1` will put the job with job ID 1 in the background.

`bg 123 456 789` will background 123, 456 and 789.

If only 123 and 789 exist, it will still background them and print an error about 456.

`bg 123 banana` or `bg banana 123` will complain that "banana" is not a valid job specifier.

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# bind - handle fish key bindings

## Synopsis

    bind [(-M | --mode) MODE] [(-m | --sets-mode) NEW_MODE]
         [(-k | --key)] SEQUENCE COMMAND [COMMAND...]
    bind [(-M | --mode) MODE] [(-k | --key)] SEQUENCE
    bind (-K | --key-names) [(-a | --all)]
    bind (-f | --function-names)
    bind (-L | --list-modes)
    bind (-e | --erase) [(-M | --mode) MODE]
         (-a | --all | [(-k | --key)] SEQUENCE [SEQUENCE...])

## Description

`bind` adds a binding for the specified key sequence to the specified command.

SEQUENCE is the character sequence to bind to. These should be written as fish escape sequences. For example, because pressing the Alt key and another character sends that character prefixed with an escape character, Alt-based key bindings can be written using the `\e` escape. For example, Alt-w can be written as `\ew`. The control character can be written in much the same way using the `\c` escape, for example Control-X (^X) can be written as `\cx`. Note that Alt-based key bindings are case sensitive and Control-based key bindings are not. This is a constraint of text-based terminals, not `fish`.

The default key binding can be set by specifying a `SEQUENCE` of the empty string (that is, `''` ). It will be used whenever no other binding matches. For most key bindings, it makes sense to use the `self-insert` function (i.e. `bind '' self-insert`) as the default keybinding. This will insert any keystrokes not specifically bound to into the editor. Non- printable characters are ignored by the editor, so this will not result in control sequences being printable.

If the `-k` switch is used, the name of the key (such as 'down', 'up' or 'backspace') is used instead of a sequence. The names used are the same as the corresponding curses variables, but without the 'key_' prefix. (See `terminfo(5)` for more information, or use `bind --key-names` for a list of all available named keys.)

`COMMAND` can be any fish command, but it can also be one of a set of special input functions. These include functions for moving the cursor, operating on the kill-ring, performing tab completion, etc. Use `bind --function-names` for a complete list of these input functions.

When `COMMAND` is a shellscript command, it is a good practice to put the actual code into a function and simply bind to the function name. This way it becomes significantly easier to test the function while editing, and the result is usually more readable as well.

If such a script produces output, the script needs to finish by calling `commandline -f repaint` in order to tell fish that a repaint is in order.

When multiple `COMMAND`s are provided, they are all run in the specified order when the key is pressed. Note that special input functions cannot be combined with ordinary shell script commands. The commands must be entirely a sequence of special input functions (from `bind -f`) or all shell script commands (i.e., valid fish script).

If no `SEQUENCE` is provided, all bindings (or just the bindings in the specified `MODE`) are printed. If `SEQUENCE` is provided without `COMMAND`, just the binding matching that sequence is printed.

Key bindings are not saved between sessions by default. Bare `bind` statements in config.fish won't have any effect because it is sourced before the default keybindings are setup. To save custom keybindings, put the `bind` statements into a function called `fish_user_key_bindings`, which will be autoloaded.

Key bindings may use "modes", which mimics Vi's modal input behavior. The default mode is "default", and every bind applies to a single mode. The mode can be viewed/changed with the `$fish_bind_mode` variable.

The following parameters are available:

- `-k` or `--key` Specify a key name, such as 'left' or 'backspace' instead of a character sequence
- `-K` or `--key-names` Display a list of available key names. Specifying `-a` or `--all` includes keys that don't have a known mapping
- `-f` or `--function-names` Display a list of available input functions
- `-L` or `--list-modes` Display a list of defined bind modes
- `-M MODE` or `--mode MODE` Specify a bind mode that the bind is used in. Defaults to "default"
- `-m NEW_MODE` or `--sets-mode NEW_MODE` Change the current mode to `NEW_MODE` after this binding is executed
- `-e` or `--erase` Erase the binding with the given sequence and mode instead of defining a new one. Multiple sequences can be specified with this flag. Specifying `-a` or `--all` with `-M` or `--mode` erases all binds in the given mode regardless of sequence. Specifying `-a` or `--all` without `-M` or `--mode` erases all binds in all modes regardless of sequence.
- `-a` or `--all` See `--erase` and `--key-names`

The following special input functions are available:

- `accept-autosuggestion`, accept the current autosuggestion completely
- `backward-char`, moves one character to the left
- `backward-bigword`, move one whitespace-delimited word to the left
- `backward-delete-char`, deletes one character of input to the left of the cursor
- `backward-kill-bigword`, move the whitespace-delimited word to the left of the cursor to the killring
- `backward-kill-line`, move everything from the beginning of the line to the cursor to the killring
- `backward-kill-path-component`, move one path component to the left of the cursor (everything from the last "/" or whitespace exclusive) to the killring
- `backward-kill-word`, move the word to the left of the cursor to the killring
- `backward-word`, move one word to the left
- `beginning-of-buffer`, moves to the beginning of the buffer, i.e. the start of the first line
- `beginning-of-history`, move to the beginning of the history
- `beginning-of-line`, move to the beginning of the line
- `begin-selection`, start selecting text
- `capitalize-word`, make the current word begin with a capital letter
- `complete`, guess the remainder of the current token
- `complete-and-search`, invoke the searchable pager on completion options (for convenience, this also moves backwards in the completion pager)
- `delete-char`, delete one character to the right of the cursor
- `downcase-word`, make the current word lowercase
- `end-of-buffer`, moves to the end of the buffer, i.e. the end of the first line
- `end-of-history`, move to the end of the history
- `end-of-line`, move to the end of the line
- `end-selection`, end selecting text
- `forward-bigword`, move one whitespace-delimited word to the right
- `forward-char`, move one character to the right
- `forward-word`, move one word to the right
- `history-search-backward`, search the history for the previous match
- `history-search-forward`, search the history for the next match
- `kill-bigword`, move the next whitespace-delimited word to the killring
- `kill-line`, move everything from the cursor to the end of the line to the killring
- `kill-selection`, move the selected text to the killring
- `kill-whole-line`, move the line to the killring
- `kill-word`, move the next word to the killring
- `suppress-autosuggestion`, remove the current autosuggestion
- `swap-selection-start-stop`, go to the other end of the highlighted text without changing the selection
- `transpose-chars`, transpose two characters to the left of the cursor
- `transpose-words`, transpose two words to the left of the cursor
- `upcase-word`, make the current word uppercase
- `yank`, insert the latest entry of the killring into the buffer
- `yank-pop`, rotate to the previous entry of the killring

## Examples

    bind \cd 'exit'

Causes `fish` to exit when Control-D is pressed.

    bind -k ppage history-search-backward

Performs a history search when the Page Up key is pressed.

    set -g fish_key_bindings fish_vi_key_bindings
    bind -M insert \cc kill-whole-line force-repaint

Turns on Vi key bindings and rebinds Control-C to clear the input line.

## Special Case: The escape Character

The escape key can be used standalone, for example, to switch from insertion mode to normal mode when using Vi keybindings. Escape may also be used as a "meta" key, to indicate the start of an escape sequence, such as function or arrow keys. Custom bindings can also be defined that begin with an escape character.

fish waits for a period after receiving the escape character, to determine whether it is standalone or part of an escape sequence. While waiting, additional key presses make the escape key behave as a meta key. If no other key presses come in, it is handled as a standalone escape. The waiting period is set to 300 milliseconds (0.3 seconds) in the default key bindings and 10 milliseconds in the vi key bindings. It can be configured by setting the `fish_escape_delay_ms` variable to a value between 10 and 5000 ms. It is recommended that this be a universal variable that you set once from an interactive session.

Note: fish 2.2.0 and earlier used a default of 10 milliseconds, and provided no way to configure it. That effectively made it impossible to use escape as a meta key.

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# block - temporarily block delivery of events

## Synopsis

    block [OPTIONS...]

## Description

`block` prevents events triggered by `fish` or the `emit` command from being delivered and acted upon while the block is in place.

In functions, `block` can be useful while performing work that should not be interrupted by the shell.

The block can be removed. Any events which triggered while the block was in place will then be delivered.

Event blocks should not be confused with code blocks, which are created with `begin`, `if`, `while` or `for`

The following parameters are available:

- `-l` or `--local` Release the block automatically at the end of the current innermost code block scope
- `-g` or `--global` Never automatically release the lock
- `-e` or `--erase` Release global block

## Example

    # Create a function that listens for events
    function --on-event foo foo; echo 'foo fired'; end

    # Block the delivery of events
    block -g

    emit foo
    # No output will be produced

    block -e
    # 'foo fired' will now be printed

## Notes

Note that events are only received from the current fish process as there is no way to send events from one fish process to another.

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# break - stop the current inner loop

## Synopsis

    LOOP_CONSTRUCT; [COMMANDS...] break; [COMMANDS...] end

## Description

`break` halts a currently running loop, such as a for loop or a while loop. It is usually added inside of a conditional block such as an if statement or a switch statement.

There are no parameters for `break`.

## Example

The following code searches all .c files for "smurf", and halts at the first occurrence.

    for i in *.c
        if grep smurf $i
            echo Smurfs are present in $i
            break
        end
    end

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# breakpoint - Launch debug mode

## Synopsis

    breakpoint

## Description

`breakpoint` is used to halt a running script and launch an interactive debugging prompt.

For more details, see Debugging fish scripts in the `fish` manual.

There are no parameters for `breakpoint`.

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# builtin - run a builtin command

## Synopsis

    builtin BUILTINNAME [OPTIONS...]

## Description

`builtin` forces the shell to use a builtin command, rather than a function or program.

The following parameters are available:

- `-n` or `--names` List the names of all defined builtins

## Example

    builtin jobs
    # executes the jobs builtin, even if a function named jobs exists

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# case - conditionally execute a block of commands

## Synopsis

    switch VALUE; [case [WILDCARD...]; [COMMANDS...]; ...] end

## Description

`switch` performs one of several blocks of commands, depending on whether a specified value equals one of several wildcarded values. `case` is used together with the `switch` statement in order to determine which block should be executed.

Each `case` command is given one or more parameters. The first `case` command with a parameter that matches the string specified in the switch command will be evaluated. `case` parameters may contain wildcards. These need to be escaped or quoted in order to avoid regular wildcard expansion using filenames.

Note that fish does not fall through on case statements. Only the first matching case is executed.

Note that command substitutions in a case statement will be evaluated even if its body is not taken. All substitutions, including command substitutions, must be performed before the value can be compared against the parameter.

## Example

If the variable $animal contains the name of an animal, the following code would attempt to classify it:

    switch $animal
        case cat
            echo evil
        case wolf dog human moose dolphin whale
            echo mammal
        case duck goose albatross
            echo bird
        case shark trout stingray
            echo fish
        # Note that the next case has a wildcard which is quoted
        case '*'
            echo I have no idea what a $animal is
    end

If the above code was run with `$animal` set to `whale`, the output would be `mammal`.

Back to command index.

# cd - change directory

## Synopsis

    cd [DIRECTORY]

## Description

`cd` changes the current working directory.

If `DIRECTORY` is supplied, it will become the new directory. If no parameter is given, the contents of the `HOME` environment variable will be used.

If `DIRECTORY` is a relative path, the paths found in the `CDPATH` environment variable array will be tried as prefixes for the specified path.

Note that the shell will attempt to change directory without requiring `cd` if the name of a directory is provided (starting with `.`, `/` or `~`, or ending with `/`).

Fish also ships a wrapper function around the builtin `cd` that understands `cd -` as changing to the previous directory. See also `prevd`. This wrapper function maintains a history of the 25 most recently visited directories in the `$dirprev` and `$dirnext` global variables. If you make those universal variables your `cd` history is shared among all fish instances.

## Examples

    cd
    # changes the working directory to your home directory.

    cd /usr/src/fish-shell
    # changes the working directory to /usr/src/fish-shell

## See Also

See also the `cdh` command for changing to a recently visited directory.

Back to command index.

# cdh - change to a recently visited directory

## Synopsis

    cdh [ directory ]

## Description

`cdh` with no arguments presents a list of recently visited directories. You can then select one of the entries by letter or number. You can also press tab to use the completion pager to select an item from the list. If you give it a single argument it is equivalent to `cd directory`.

Note that the `cd` command limits directory history to the 25 most recently visited directories. The history is stored in the `$dirprev` and `$dirnext` variables which this command manipulates. If you make those universal variables your `cd` history is shared among all fish instances.

## See Also

See also the `prevd` and `pushd` commands which also work with the recent `cd` history and are provided for compatibility with other shells.

Back to command index.

# command - run a program

## Synopsis

    command [OPTIONS] COMMANDNAME [ARGS...]

## Description

`command` forces the shell to execute the program `COMMANDNAME` and ignore any functions or builtins with the same name.

The following options are available:

- `-a` or `--all` returns all the external commands that are found in `$PATH` in the order they are found.
- `-s` or `--search` returns the name of the external command that would be executed, or nothing if no file with the specified name could be found in the `$PATH`.

With the `-s` option, `command` treats every argument as a separate command to look up and sets the exit status to 0 if any of the specified commands were found, or 1 if no commands could be found. Additionally passing a `-q` or `--quiet` option prevents any paths from being printed, like the `type -q`, for testing only the exit status.

For basic compatibility with POSIX `command`, the `-v` flag is recognized as an alias for `-s`.

## Examples

`command ls` causes fish to execute the `ls` program, even if an `ls` function exists.

`command -s ls` returns the path to the `ls` program.

Back to command index.

# commandline - set or get the current command line buffer

## Synopsis

    commandline [OPTIONS] [CMD]

## Description

`commandline` can be used to set or get the current contents of the command line buffer.

With no parameters, `commandline` returns the current value of the command line.

With `CMD` specified, the command line buffer is erased and replaced with the contents of `CMD`.

The following options are available:

- `-C` or `--cursor` set or get the current cursor position, not the contents of the buffer. If no argument is given, the current cursor position is printed, otherwise the argument is interpreted as the new cursor position.
- `-f` or `--function` inject readline functions into the reader. This option cannot be combined with any other option. It will cause any additional arguments to be interpreted as readline functions, and these functions will be injected into the reader, so that they will be returned to the reader before any additional actual key presses are read.

The following options change the way `commandline` updates the command line buffer:

- `-a` or `--append` do not remove the current commandline, append the specified string at the end of it
- `-i` or `--insert` do not remove the current commandline, insert the specified string at the current cursor position
- `-r` or `--replace` remove the current commandline and replace it with the specified string (default)

The following options change what part of the commandline is printed or updated:

- `-b` or `--current-buffer` select the entire buffer (default)
- `-j` or `--current-job` select the current job
- `-p` or `--current-process` select the current process
- `-t` or `--current-token` select the current token.

The following options change the way `commandline` prints the current commandline buffer:

- `-c` or `--cut-at-cursor` only print selection up until the current cursor position
- `-o` or `--tokenize` tokenize the selection and print one string-type token per line

If `commandline` is called during a call to complete a given string using `complete -C STRING`, `commandline` will consider the specified string to be the current contents of the command line.

The following options output metadata about the commandline state:

- `-L` or `--line` print the line that the cursor is on, with the topmost line starting at 1
- `-S` or `--search-mode` evaluates to true if the commandline is performing a history search
- `-P` or `--paging-mode` evaluates to true if the commandline is showing pager contents, such as tab completions

## Example

`commandline -j $history[3]` replaces the job under the cursor with the third item from the command line history.

If the commandline contains

    > echo $flounder >&2 | less; and echo $catfish

(with the cursor on the "o" of "flounder")

Then the following invocations behave like this:

    > commandline -t
    $flounder
    > commandline -ct
    $fl
    > commandline -b ## or just commandline
    echo $flounder >&2 | less; and echo $catfish
    > commandline -p
    echo $flounder >&2
    > commandline -j
    echo $flounder >&2 | less

Back to command index.

# complete - edit command specific tab-completions

## Synopsis

    complete ( -c | --command | -p | --path ) COMMAND
            [( -c | --command | -p | --path ) COMMAND]...
            [( -e | --erase )]
            [( -s | --short-option ) SHORT_OPTION]...
            [( -l | --long-option | -o | --old-option ) LONG_OPTION]...
            [( -a | --arguments ) OPTION_ARGUMENTS]
            [( -f | --no-files )]
            [( -r | --require-parameter )]
            [( -x | --exclusive )]
            [( -w | --wraps ) WRAPPED_COMMAND]...
            [( -n | --condition ) CONDITION]
            [( -d | --description ) DESCRIPTION]
    complete ( -C[STRING] | --do-complete[=STRING] )

## Description

For an introduction to specifying completions, see Writing your own completions in the fish manual.

- `COMMAND` is the name of the command for which to add a completion.
- `SHORT_OPTION` is a one character option for the command.
- `LONG_OPTION` is a multi character option for the command.
- `OPTION_ARGUMENTS` is parameter containing a space-separated list of possible option-arguments, which may contain command substitutions.
- `DESCRIPTION` is a description of what the option and/or option arguments do.
- `-c COMMAND` or `--command COMMAND` specifies that `COMMAND` is the name of the command.
- `-p COMMAND` or `--path COMMAND` specifies that `COMMAND` is the absolute path of the program (optionally containing wildcards).
- `-e` or `--erase` deletes the specified completion.
- `-s SHORT_OPTION` or `--short-option=SHORT_OPTION` adds a short option to the completions list.
- `-l LONG_OPTION` or `--long-option=LONG_OPTION` adds a GNU style long option to the completions list.
- `-o LONG_OPTION` or `--old-option=LONG_OPTION` adds an old style long option to the completions list (See below for details).
- `-a OPTION_ARGUMENTS` or `--arguments=OPTION_ARGUMENTS` adds the specified option arguments to the completions list.
- `-f` or `--no-files` specifies that the options specified by this completion may not be followed by a filename.
- `-r` or `--require-parameter` specifies that the options specified by this completion always must have an option argument, i.e. may not be followed by another option.
- `-x` or `--exclusive` implies both `-r` and `-f`.
- `-w WRAPPED_COMMAND` or `--wraps=WRAPPED_COMMAND` causes the specified command to inherit completions from the wrapped command (See below for details).
- `-n` or `--condition` specifies a shell command that must return 0 if the completion is to be used. This makes it possible to specify completions that should only be used in some cases.
- `-CSTRING` or `--do-complete=STRING` makes complete try to find all possible completions for the specified string.
- `-C` or `--do-complete` with no argument makes complete try to find all possible completions for the current command line buffer. If the shell is not in interactive mode, an error is returned.
- `-A` and `--authoritative` no longer do anything and are silently ignored.
- `-u` and `--unauthoritative` no longer do anything and are silently ignored.

Command specific tab-completions in `fish` are based on the notion of options and arguments. An option is a parameter which begins with a hyphen, such as '`-h`', '`-help`' or '`--help`'. Arguments are parameters that do not begin with a hyphen. Fish recognizes three styles of options, the same styles as the GNU version of the getopt library. These styles are:

- Short options, like '`-a`'. Short options are a single character long, are preceded by a single hyphen and may be grouped together (like '`-la`', which is equivalent to '`-l -a`'). Option arguments may be specified in the following parameter ('`-w 32`') or by appending the option with the value ('`-w32`').
- Old style long options, like '`-Wall`'. Old style long options can be more than one character long, are preceded by a single hyphen and may not be grouped together. Option arguments are specified in the following parameter ('`-ao null`').
- GNU style long options, like '`--colors`'. GNU style long options can be more than one character long, are preceded by two hyphens, and may not be grouped together. Option arguments may be specified in the following parameter ('`--quoting-style shell`') or by appending the option with a '`=`' and the value ('`--quoting-style=shell`'). GNU style long options may be abbreviated so long as the abbreviation is unique ('`--h`') is equivalent to '`--help`' if help is the only long option beginning with an 'h').

The options for specifying command name and command path may be used multiple times to define the same completions for multiple commands.

The options for specifying command switches and wrapped commands may be used multiple times to define multiple completions for the command(s) in a single call.

Invoking `complete` multiple times for the same command adds the new definitions on top of any existing completions defined for the command.

When `-a` or `--arguments` is specified in conjunction with long, short, or old style options, the specified arguments are only used as completions when attempting to complete an argument for any of the specified options. If `-a` or `--arguments` is specified without any long, short, or old style options, the specified arguments are used when completing any argument to the command (except when completing an option argument that was specified with `-r` or `--require-parameter`).

Command substitutions found in `OPTION_ARGUMENTS` are not expected to return a space-separated list of arguments. Instead they must return a newline-separated list of arguments, and each argument may optionally have a tab character followed by the argument description. Any description provided in this way overrides a description given with `-d` or `--description`.

The `-w` or `--wraps` options causes the specified command to inherit completions from another command. The inheriting command is said to "wrap" the inherited command. The wrapping command may have its own completions in addition to inherited ones. A command may wrap multiple commands, and wrapping is transitive: if A wraps B, and B wraps C, then A automatically inherits all of C's completions. Wrapping can be removed using the `-e` or `--erase` options. Note that wrapping only works for completions specified with `-c` or `--command` and are ignored when specifying completions with `-p` or `--path`.

When erasing completions, it is possible to either erase all completions for a specific command by specifying `complete -c COMMAND -e`, or by specifying a specific completion option to delete by specifying either a long, short or old style option.

## Example

The short style option `-o` for the `gcc` command requires that a file follows it. This can be done using writing:

    complete -c gcc -s o -r

The short style option `-d` for the `grep` command requires that one of the strings '`read`', '`skip`' or '`recurse`' is used. This can be specified writing:

    complete -c grep -s d -x -a "read skip recurse"

The `su` command takes any username as an argument. Usernames are given as the first colon-separated field in the file /etc/passwd. This can be specified as:

    complete -x -c su -d "Username" -a "(cat /etc/passwd | cut -d : -f 1)"

The `rpm` command has several different modes. If the `-e` or `--erase` flag has been specified, `rpm` should delete one or more packages, in which case several switches related to deleting packages are valid, like the `nodeps` switch.

This can be written as:

    complete -c rpm -n "__fish_contains_opt -s e erase" -d nodeps "Don't check dependencies"

where `__fish_contains_opt` is a function that checks the command line buffer for the presence of a specified set of options.

To implement an alias, use the `-w` or `--wraps` option:

    complete -c hub -w git

Now hub inherits all of the completions from git. Note this can also be specified in a function declaration.

Back to command index.

# contains - test if a word is present in a list

## Synopsis

    contains [OPTIONS] KEY [VALUES...]

## Description

`contains` tests whether the set `VALUES` contains the string `KEY`. If so, `contains` exits with status 0; if not, it exits with status 1.

The following options are available:

- `-i` or `--index` print the word index

Note that, like GNU tools, `contains` interprets all arguments starting with a `-` as options to contains, until it reaches an argument that is `--` (two dashes). See the examples below.

## Example

    for i in ~/bin /usr/local/bin
        if not contains $i $PATH
            set PATH $PATH $i
        end
    end

The above code tests if `~/bin` and `/usr/local/bin` are in the path and adds them if not.

    function hasargs
        if contains -- -q $argv
            echo '$argv contains a -q option'
        end
    end

The above code checks for `-q` in the argument list, using the `--` argument to demarcate options to `contains` from the key to search for.

Back to command index.

# continue - skip the remainder of the current iteration of the current inner loop

## Synopsis

    LOOP_CONSTRUCT; [COMMANDS...;] continue; [COMMANDS...;] end

## Description

`continue` skips the remainder of the current iteration of the current inner loop, such as a for loop or a while loop. It is usually added inside of a conditional block such as an if statement or a switch statement.

## Example

The following code removes all tmp files that do not contain the word smurf.

    for i in *.tmp
        if grep smurf $i
            continue
        end
        rm $i
    end

Back to command index.

# count - count the number of elements of an array

## Synopsis

    count $VARIABLE

## Description

`count` prints the number of arguments that were passed to it. This is usually used to find out how many elements an environment variable array contains.

`count` does not accept any options, including `-h` or `--help`.

`count` exits with a non-zero exit status if no arguments were passed to it, and with zero if at least one argument was passed.

## Example

    count $PATH
    # Returns the number of directories in the users PATH variable.

    count *.txt
    # Returns the number of files in the current working directory ending with the suffix '.txt'.

Back to command index.

# dirh - print directory history

## Synopsis

    dirh

## Description

`dirh` prints the current directory history. The current position in the history is highlighted using the color defined in the `fish_color_history_current` environment variable.

`dirh` does not accept any parameters.

Note that the `cd` command limits directory history to the 25 most recently visited directories. The history is stored in the `$dirprev` and `$dirnext` variables.

Back to command index.

# dirs - print directory stack

## Synopsis

    dirs
    dirs -c

## Description

`dirs` prints the current directory stack, as created by the `pushd` command.

With "-c", it clears the directory stack instead.

`dirs` does not accept any parameters.

Back to command index.

# disown - remove a process from the list of jobs

## Synopsis

    disown [ PID ... ]

## Description

`disown` removes the specified job from the list of jobs. The job itself continues to exist, but fish does not keep track of it any longer.

Jobs in the list of jobs are sent a hang-up signal when fish terminates, which usually causes the job to terminate; `disown` allows these processes to continue regardless.

If no process is specified, the most recently-used job is removed (like `bg` and `fg`). If one or more `PID`s are specified, jobs with the specified process IDs are removed from the job list. Invalid jobs are ignored and a warning is printed.

If a job is stopped, it is sent a signal to continue running, and a warning is printed. It is not possible to use the `bg` builtin to continue a job once it has been disowned.

The PID of the desired process is usually found by using process expansion, which can specify jobs or search by process name.

`disown` returns 0 if all specified jobs were disowned successfully, and 1 if any problems were encountered.

## Example

`firefox &; disown` will start the Firefox web browser in the background and remove it from the job list, meaning it will not be closed when the fish process is closed.

`disown (jobs -p)` removes all jobs from the job list without terminating them.

Back to command index.

# echo - display a line of text

## Synopsis

    echo [OPTIONS] [STRING]

## Description

`echo` displays a string of text.

The following options are available:

- `-n`, Do not output a newline
- `-s`, Do not separate arguments with spaces
- `-E`, Disable interpretation of backslash escapes (default)
- `-e`, Enable interpretation of backslash escapes

## Escape Sequences

If `-e` is used, the following sequences are recognized:

- `\` backslash
- `\a` alert (BEL)
- `\b` backspace
- `\c` produce no further output
- `\e` escape
- `\f` form feed
- `\n` new line
- `\r` carriage return
- `\t` horizontal tab
- `\v` vertical tab
- `\0NNN` byte with octal value NNN (1 to 3 digits)
- `\xHH` byte with hexadecimal value HH (1 to 2 digits)

## Example

    echo 'Hello World'

Print hello world to stdout

    echo -e 'Top\nBottom'

Print Top and Bottom on separate lines, using an escape sequence

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# else - execute command if a condition is not met

## Synopsis

    if CONDITION; COMMANDS_TRUE...; [else; COMMANDS_FALSE...;] end

## Description

`if` will execute the command `CONDITION`. If the condition's exit status is 0, the commands `COMMANDS_TRUE` will execute. If it is not 0 and `else` is given, `COMMANDS_FALSE` will be executed.

## Example

The following code tests whether a file `foo.txt` exists as a regular file.

    if test -f foo.txt
        echo foo.txt exists
    else
        echo foo.txt does not exist
    end

Back to command index.

# emit - Emit a generic event

## Synopsis

    emit EVENT_NAME [ARGUMENTS...]

## Description

`emit` emits, or fires, an event. Events are delivered to, or caught by, special functions called event handlers. The arguments are passed to the event handlers as function arguments.

## Example

The following code first defines an event handler for the generic event named 'test_event', and then emits an event of that type.

    function event_test --on-event test_event
        echo event test: $argv
    end

    emit test_event something

    \subsection emit-notes Notes

    Note that events are only sent to the current fish process as there is no way to send events from one fish process to another.

Back to command index.

# end - end a block of commands.

## Synopsis

    begin; [COMMANDS...] end
    if CONDITION; COMMANDS_TRUE...; [else; COMMANDS_FALSE...;] end
    while CONDITION; COMMANDS...; end
    for VARNAME in [VALUES...]; COMMANDS...; end
    switch VALUE; [case [WILDCARD...]; [COMMANDS...]; ...] end

## Description

`end` ends a block of commands.

For more information, read the documentation for the block constructs, such as `if`, `for` and `while`.

The `end` command does not change the current exit status. Instead, the status after it will be the status returned by the most recent command.

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# eval - evaluate the specified commands

## Synopsis

    eval [COMMANDS...]

## Description

`eval` evaluates the specified parameters as a command. If more than one parameter is specified, all parameters will be joined using a space character as a separator.

## Example

The following code will call the ls command. Note that `fish` does not support the use of shell variables as direct commands; `eval` can be used to work around this.

    set cmd ls
    eval $cmd

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# exec - execute command in current process

## Synopsis

    exec COMMAND [OPTIONS...]

## Description

`exec` replaces the currently running shell with a new command. On successful completion, `exec` never returns. `exec` cannot be used inside a pipeline.

## Example

`exec emacs` starts up the emacs text editor, and exits `fish`. When emacs exits, the session will terminate.

Back to command index.

# exit - exit the shell

## Synopsis

    exit [STATUS]

## Description

`exit` causes fish to exit. If `STATUS` is supplied, it will be converted to an integer and used as the exit code. Otherwise, the exit code will be that of the last command executed.

If exit is called while sourcing a file (using the source builtin) the rest of the file will be skipped, but the shell itself will not exit.

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# false - return an unsuccessful result

## Synopsis

    false

## Description

`false` sets the exit status to 1.

Back to command index.

# fg - bring job to foreground

## Synopsis

    fg [PID]

## Description

`fg` brings the specified job to the foreground, resuming it if it is stopped. While a foreground job is executed, fish is suspended. If no job is specified, the last job to be used is put in the foreground. If PID is specified, the job with the specified group ID is put in the foreground.

The PID of the desired process is usually found by using process expansion. Fish is capable of expanding far more than just the numeric PID, including referencing itself and finding PIDs by name.

## Example

`fg %1` will put the job with job ID 1 in the foreground.

Back to command index.

# fish - the friendly interactive shell

## Synopsis

    fish [OPTIONS] [-c command] [FILE [ARGUMENTS...]]

## Description

`fish` is a command-line shell written mainly with interactive use in mind. The full manual is available in HTML by using the help command from inside fish.

The following options are available:

- `-c` or `--command=COMMANDS` evaluate the specified commands instead of reading from the commandline
- `-C` or `--init-command=COMMANDS` evaluate the specified commands after reading the configuration, before running the command specified by `-c` or reading interactive input
- `-d` or `--debug-level=DEBUG_LEVEL` specify the verbosity level of fish. A higher number means higher verbosity. The default level is 1.
- `-i` or `--interactive` specify that fish is to run in interactive mode
- `-l` or `--login` specify that fish is to run as a login shell
- `-n` or `--no-execute` do not execute any commands, only perform syntax checking
- `-p` or `--profile=PROFILE_FILE` when fish exits, output timing information on all executed commands to the specified file
- `-v` or `--version` display version and exit
- `-D` or `--debug-stack-frames=DEBUG_LEVEL` specify how many stack frames to display when debug messages are written. The default is zero. A value of 3 or 4 is usually sufficient to gain insight into how a given debug call was reached but you can specify a value up to 128.

The fish exit status is generally the exit status of the last foreground command. If fish is exiting because of a parse error, the exit status is 127.

Back to command index.

# fish_breakpoint_prompt - define the appearance of the command line prompt when in the context of a `breakpoint` command

## Synopsis

    function fish_breakpoint_prompt
        ...
    end

## Description

By defining the `fish_breakpoint_prompt` function, the user can choose a custom prompt when asking for input in response to a `breakpoint` command. The `fish_breakpoint_prompt` function is executed when the prompt is to be shown, and the output is used as a prompt.

The exit status of commands within `fish_breakpoint_prompt` will not modify the value of $status outside of the `fish_breakpoint_prompt` function.

`fish` ships with a default version of this function that displays the function name and line number of the current execution context.

## Example

A simple prompt that is a simplified version of the default debugging prompt:

    function fish_breakpoint_prompt -d "Write out the debug prompt"
        set -l function (status current-function)
        set -l line (status current-line-number)
        set -l prompt "$function:$line >"
        echo -ns (set_color $fish_color_status) \ (set_color normal)
    end

Back to command index.

# fish_config - start the web-based configuration interface

## Description

`fish_config` starts the web-based configuration interface.

The web interface allows you to view your functions, variables and history, and to make changes to your prompt and color configuration.

`fish_config` starts a local web server and then opens a web browser window; when you have finished, close the browser window and then press the Enter key to terminate the configuration session.

`fish_config` optionally accepts name of the initial configuration tab. For e.g. `fish_config history` will start configuration interface with history tab.

If the `BROWSER` environment variable is set, it will be used as the name of the web browser to open instead of the system default.

## Example

`fish_config` opens a new web browser window and allows you to configure certain fish settings.

Back to command index.

# fish_indent - indenter and prettifier

## Synopsis

    fish_indent [OPTIONS]

## Description

`fish_indent` is used to indent a piece of fish code. `fish_indent` reads commands from standard input and outputs them to standard output or a specified file.

The following options are available:

- `-w` or `--write` indents a specified file and immediately writes to that file.
- `-i` or `--no-indent` do not indent commands; only reformat to one job per line.
- `-v` or `--version` displays the current fish version and then exits.
- `--ansi` colorizes the output using ANSI escape sequences, appropriate for the current $TERM, using the colors defined in the environment (such as `$fish_color_command`).
- `--html` outputs HTML, which supports syntax highlighting if the appropriate CSS is defined. The CSS class names are the same as the variable names, such as `fish_color_command`.
- `-d` or `--debug-level=DEBUG_LEVEL` enables debug output and specifies a verbosity level (like `fish -d`). Defaults to 0.
- `-D` or `--debug-stack-frames=DEBUG_LEVEL` specify how many stack frames to display when debug messages are written. The default is zero. A value of 3 or 4 is usually sufficient to gain insight into how a given debug call was reached but you can specify a value up to 128.
- `--dump-parse-tree` dumps information about the parsed statements to stderr. This is likely to be of interest only to people working on the fish source code.

Back to command index.

# fish_key_reader - explore what characters keyboard keys send

## Synopsis

    fish_key_reader [OPTIONS]

## Description

`fish_key_reader` is used to study input received from the terminal and can help with key binds. The program is interactive and works on standard input. Individual characters themselves and their hexadecimal values are displayed.

The tool will write an example `bind` command matching the character sequence captured to stdout. If the character sequence matches a special key name (see `bind --key-names`), both `bind CHARS ...` and `bind -k KEYNAME ...` usage will be shown. Additional details about the characters received, such as the delay between chars, are written to stderr.

The following options are available:

- `-c` or `--continuous` begins a session where multiple key sequences can be inspected. By default the program exits after capturing a single key sequence.
- `-d` or `--debug-level=DEBUG_LEVEL` enables debug output and specifies a verbosity level (like `fish -d`). Defaults to 0.
- `-D` or `--debug-stack-frames=DEBUG_LEVEL` specify how many stack frames to display when debug messages are written. The default is zero. A value of 3 or 4 is usually sufficient to gain insight into how a given debug call was reached but you can specify a value up to 128.
- `-h` or `--help` prints usage information.
- `-v` or `--version` prints fish_key_reader's version and exits.

## Usage Notes

The delay in milliseconds since the previous character was received is included in the diagnostic information written to stderr. This information may be useful to determine the optimal `fish_escape_delay_ms` setting or learn the amount of lag introduced by tools like `ssh`, `mosh` or `tmux`.

`fish_key_reader` intentionally disables handling of many signals. To terminate `fish_key_reader` in `--continuous` mode do:

- press `Ctrl-C` twice, or
- press `Ctrl-D` twice, or
- type `exit`, or
- type `quit`

Back to command index.

# fish_mode_prompt - define the appearance of the mode indicator

## Synopsis

The fish_mode_prompt function will output the mode indicator for use in vi-mode.

## Description

The default `fish_mode_prompt` function will output indicators about the current Vi editor mode displayed to the left of the regular prompt. Define your own function to customize the appearance of the mode indicator. You can also define an empty `fish_mode_prompt` function to remove the Vi mode indicators. The `$fish_bind_mode variable` can be used to determine the current mode. It will be one of `default`, `insert`, `replace_one`, or `visual`.

## Example

    function fish_mode_prompt
      switch $fish_bind_mode
        case default
          set_color --bold red
          echo 'N'
        case insert
          set_color --bold green
          echo 'I'
        case replace_one
          set_color --bold green
          echo 'R'
        case visual
          set_color --bold brmagenta
          echo 'V'
        case '*'
          set_color --bold red
          echo '?'
      end
      set_color normal
    end

Outputting multiple lines is not supported in `fish_mode_prompt`.

Back to command index.

# fish_opt - create an option spec for the argparse command

## Synopsis

    fish_opt [ -h | --help ]
    fish_opt ( -s X | --short=X ) [ -l LONG | --long=LONG ] [ --long-only ] \
        [ -o | --optional-val ] [ -r | --required-val ] [ --multiple-vals ]

## Description

This command provides a way to produce option specifications suitable for use with the `argparse` command. You can, of course, write the option specs by hand without using this command. But you might prefer to use this for the clarity it provides.

The following `argparse` options are available:

- `-s` or `--short` takes a single letter that is used as the short flag in the option being defined. This option is mandatory.
- `-l` or `--long` takes a string that is used as the long flag in the option being defined. This option is optional and has no default. If no long flag is defined then only the short flag will be allowed when parsing arguments using the option spec.
- `--long-only` means the option spec being defined will only allow the long flag name to be used. The short flag name must still be defined (i.e., `--short` must be specified) but it cannot be used when parsing args using this option spec.
- `-o` or `--optional` means the option being defined can take a value but it is optional rather than required. If the option is seen more than once when parsing arguments only the last value seen is saved. This means the resulting flag variable created by `argparse` will zero elements if no value was given with the option else it will have exactly one element.
- `-r` or `--required` means the option being defined requires a value. If the option is seen more than once when parsing arguments only the last value seen is saved. This means the resulting flag variable created by `argparse` will have exactly one element.
- `--multiple-vals` means the option being defined requires a value each time it is seen. Each instance is stored. This means the resulting flag variable created by `argparse` will have one element for each instance of this option in the args.
- `-h` or `--help` displays help about using this command.

## Examples

Define a single option spec for the boolean help flag:

    set -l options (fish_opt -s h -l help)
    argparse $options -- $argv

Same as above but with a second flag that requires a value:

    set -l options (fish_opt -s h -l help)
    set options $options (fish_opt -s m -l max --required-val)
    argparse $options -- $argv

Same as above but with a third flag that can be given multiple times saving the value of each instance seen and only the long flag name (`--token`) can be used:

    set -l options (fish_opt --short=h --long=help)
    set options $options (fish_opt --short=m --long=max --required-val)
    set options $options (fish_opt --short=t --long=token --multiple-vals --long-only)
    argparse $options -- $argv

Back to command index.

# fish_prompt - define the appearance of the command line prompt

## Synopsis

    function fish_prompt
        ...
    end

## Description

By defining the `fish_prompt` function, the user can choose a custom prompt. The `fish_prompt` function is executed when the prompt is to be shown, and the output is used as a prompt.

The exit status of commands within `fish_prompt` will not modify the value of $status outside of the `fish_prompt` function.

`fish` ships with a number of example prompts that can be chosen with the `fish_config` command.

## Example

A simple prompt:

    function fish_prompt -d "Write out the prompt"
        printf '%s@%s%s%s%s> ' (whoami) (hostname | cut -d . -f 1) \
                (set_color $fish_color_cwd) (prompt_pwd) (set_color normal)
    end

Back to command index.

# fish_right_prompt - define the appearance of the right-side command line prompt

## Synopsis

    function fish_right_prompt
        ...
    end

## Description

`fish_right_prompt` is similar to `fish_prompt`, except that it appears on the right side of the terminal window.

Multiple lines are not supported in `fish_right_prompt`.

## Example

A simple right prompt:

    function fish_right_prompt -d "Write out the right prompt"
        date '+%m/%d/%y'
    end

Back to command index.

# fish_update_completions - Update completions using manual pages

## Description

`fish_update_completions` parses manual pages installed on the system, and attempts to create completion files in the `fish` configuration directory.

This does not overwrite custom completions.

There are no parameters for `fish_update_completions`.

Back to command index.

# fish_vi_mode - Enable vi mode

## Synopsis

    fish_vi_mode

## Description

This function is deprecated. Please call `fish_vi_key_bindings directly`

`fish_vi_mode` enters a vi-like command editing mode. To always start in vi mode, add `fish_vi_mode` to your `config.fish` file.

Back to command index.

# for - perform a set of commands multiple times.

## Synopsis

    for VARNAME in [VALUES...]; COMMANDS...; end

## Description

`for` is a loop construct. It will perform the commands specified by `COMMANDS` multiple times. On each iteration, the local variable specified by `VARNAME` is assigned a new value from `VALUES`. If `VALUES` is empty, `COMMANDS` will not be executed at all.

## Example

    for i in foo bar baz; echo $i; end

    # would output:
    foo
    bar
    baz

Back to command index.

# funced - edit a function interactively

## Synopsis

    funced [OPTIONS] NAME

## Description

`funced` provides an interface to edit the definition of the function `NAME`.

If the `$VISUAL` environment variable is set, it will be used as the program to edit the function. If `$VISUAL` is unset but `$EDITOR` is set, that will be used. Otherwise, a built-in editor will be used. Note that to enter a literal newline using the built-in editor you should press Alt-Enter. Pressing Enter signals that you are done editing the function. This does not apply to an external editor like emacs or vim.

If there is no function called `NAME` a new function will be created with the specified name

- `-e command` or `--editor command` Open the function body inside the text editor given by the command (for example, `-e vi`). The special command `fish` will use the built-in editor (same as specifying `-i`).
- `-i` or `--interactive` Force opening the function body in the built-in editor even if `$VISUAL` or `$EDITOR` is defined.

Back to command index.

# funcsave - save the definition of a function to the user's autoload directory

## Synopsis

    funcsave FUNCTION_NAME

## Description

`funcsave` saves the current definition of a function to a file in the fish configuration directory. This function will be automatically loaded by current and future fish sessions. This can be useful if you have interactively created a new function and wish to save it for later use.

Note that because fish loads functions on-demand, saved functions will not function as event handlers until they are run or sourced otherwise. To activate an event handler for every new shell, add the function to your shell initialization file instead of using `funcsave`.

Back to command index.

# function - create a function

## Synopsis

    function NAME [OPTIONS]; BODY; end

## Description

`function` creates a new function `NAME` with the body `BODY`.

A function is a list of commands that will be executed when the name of the function is given as a command.

The following options are available:

- `-a NAMES` or `--argument-names NAMES` assigns the value of successive command-line arguments to the names given in NAMES.
- `-d DESCRIPTION` or `--description=DESCRIPTION` is a description of what the function does, suitable as a completion description.
- `-w WRAPPED_COMMAND` or `--wraps=WRAPPED_COMMAND` causes the function to inherit completions from the given wrapped command. See the documentation for `complete` for more information.
- `-e` or `--on-event EVENT_NAME` tells fish to run this function when the specified named event is emitted. Fish internally generates named events e.g. when showing the prompt.
- `-v` or `--on-variable VARIABLE_NAME` tells fish to run this function when the variable VARIABLE_NAME changes value.
- `-j PGID` or `--on-job-exit PGID` tells fish to run this function when the job with group ID PGID exits. Instead of PGID, the string 'caller' can be specified. This is only legal when in a command substitution, and will result in the handler being triggered by the exit of the job which created this command substitution.
- `-p PID` or `--on-process-exit PID` tells fish to run this function when the fish child process with process ID PID exits.
- `-s` or `--on-signal SIGSPEC` tells fish to run this function when the signal SIGSPEC is delivered. SIGSPEC can be a signal number, or the signal name, such as SIGHUP (or just HUP).
- `-S` or `--no-scope-shadowing` allows the function to access the variables of calling functions. Normally, any variables inside the function that have the same name as variables from the calling function are "shadowed", and their contents is independent of the calling function.
- `-V` or `--inherit-variable NAME` snapshots the value of the variable `NAME` and defines a local variable with that same name and value when the function is defined. This is similar to a closure in other languages like Python but a bit different. Note the word "snapshot" in the first sentence. If you change the value of the variable after defining the function, even if you do so in the same scope (typically another function) the new value will not be used by the function you just created using this option. See the `function notify` example below for how this might be used.

If the user enters any additional arguments after the function, they are inserted into the environment variable array `$argv`. If the `--argument-names` option is provided, the arguments are also assigned to names specified in that option.

By using one of the event handler switches, a function can be made to run automatically at specific events. The user may generate new events using the emit builtin. Fish generates the following named events:

- `fish_prompt`, which is emitted whenever a new fish prompt is about to be displayed.
- `fish_command_not_found`, which is emitted whenever a command lookup failed.

- `fish_preexec`, which is emitted right before executing an interactive command. The commandline is passed as the first parameter.

  Note: This event will be emitted even if the command is invalid. The commandline parameter includes the entire commandline verbatim, and may potentially include newlines.

- `fish_postexec`, which is emitted right after executing an interactive command. The commandline is passed as the first parameter.

  Note: This event will be emitted even if the command is invalid. The commandline parameter includes the entire commandline verbatim, and may potentially include newlines.

## Example

    function ll
        ls -l $argv
    end

will run the `ls` command, using the `-l` option, while passing on any additional files and switches to `ls`.

    function mkdir -d "Create a directory and set CWD"
        command mkdir $argv
        if test $status = 0
            switch $argv[(count $argv)]
                case '-*'

                case '*'
                    cd $argv[(count $argv)]
                    return
            end
        end
    end

This will run the `mkdir` command, and if it is successful, change the current working directory to the one just created.

    function notify
        set -l job (jobs -l -g)
        or begin; echo "There are no jobs" >&2; return 1; end

        function _notify_job_$job --on-job-exit $job --inherit-variable job
            echo -n \a ## beep
            functions -e _notify_job_$job
        end
    end

This will beep when the most recent job completes.

## Notes

Note that events are only received from the current fish process as there is no way to send events from one fish process to another.

Back to command index.

# functions - print or erase functions

## Synopsis

    functions [ -a | --all ] [ -n | --names ]
    functions [ -D | --details ] [ -v ] FUNCTION
    functions -c OLDNAME NEWNAME
    functions -d DESCRIPTION FUNCTION
    functions [ -e | -q ] FUNCTIONS...

## Description

`functions` prints or erases functions.

The following options are available:

- `-a` or `--all` lists all functions, even those whose name starts with an underscore.
- `-c OLDNAME NEWNAME` or `--copy OLDNAME NEWNAME` creates a new function named NEWNAME, using the definition of the OLDNAME function.
- `-d DESCRIPTION` or `--description=DESCRIPTION` changes the description of this function.
- `-e` or `--erase` causes the specified functions to be erased.
- `-D` or `--details` reports the path name where each function is defined or could be autoloaded, `stdin` if the function was defined interactively or on the command line or by reading stdin, and `n/a` if the function isn't available. If the `--verbose` option is also specified then five lines are written:
  1. the pathname as already described,
  2. `autoloaded`, `not-autoloaded` or `n/a`,
  3. the line number within the file or zero if not applicable,
  4. `scope-shadowing` if the function shadows the vars in the calling function (the normal case if it wasn't defined with `--no-scope-shadowing`), else `no-scope-shadowing`, or `n/a` if the function isn't defined,
  5. the function description minimally escaped so it is a single line or `n/a` if the function isn't defined.

You should not assume that only five lines will be written since we may add additional information to the output in the future.

- `-n` or `--names` lists the names of all defined functions.
- `-q` or `--query` tests if the specified functions exist.
- `-v` or `--verbose` will make some output more verbose.

The default behavior of `functions`, when called with no arguments, is to print the names of all defined functions. Unless the `-a` option is given, no functions starting with underscores are not included in the output.

If any non-option parameters are given, the definition of the specified functions are printed.

Automatically loaded functions cannot be removed using `functions -e`. Either remove the definition file or change the $fish_function_path variable to remove autoloaded functions.

Copying a function using `-c` copies only the body of the function, and does not attach any event notifications from the original function.

Only one function's description can be changed in a single invocation of `functions -d`.

The exit status of `functions` is the number of functions specified in the argument list that do not exist, which can be used in concert with the `-q` option.

## Examples

    functions -n
    # Displays a list of currently-defined functions

    functions -c foo bar
    # Copies the 'foo' function to a new function called 'bar'

    functions -e bar
    # Erases the function `bar`

Back to command index.

# help - display fish documentation

## Synopsis

    help [SECTION]

## Description

`help` displays the fish help documentation.

If a `SECTION` is specified, the help for that command is shown.

If the BROWSER environment variable is set, it will be used to display the documentation. Otherwise, fish will search for a suitable browser.

If you prefer to use a different browser (other than as described above) for fish help, you can set the fish_help_browser variable. This variable may be set as an array, where the first element is the browser command and the rest are browser options.

Note that most builtin commands display their help in the terminal when given the `--help` option.

## Example

`help fg` shows the documentation for the `fg` builtin.

Back to command index.

# history - Show and manipulate command history

## Synopsis

    history search [ --show-time ] [ --case-sensitive ] [ --exact | --prefix | --contains ] [ --max=n ] [ --null ] [ "search string"... ]
    history delete [ --show-time ] [ --case-sensitive ] [ --exact | --prefix | --contains ] "search string"...
    history merge
    history save
    history clear
    history ( -h | --help )

## Description

`history` is used to search, delete, and otherwise manipulate the history of interactive commands.

The following operations (sub-commands) are available:

- `search` returns history items matching the search string. If no search string is provided it returns all history items. This is the default operation if no other operation is specified. You only have to explicitly say `history search` if you wish to search for one of the subcommands. The `--contains` search option will be used if you don't specify a different search option. Entries are ordered newest to oldest. If stdout is attached to a tty the output will be piped through your pager by the history function. The history builtin simply writes the results to stdout.
- `delete` deletes history items. Without the `--prefix` or `--contains` options, the exact match of the specified text will be deleted. If you don't specify `--exact` a prompt will be displayed before any items are deleted asking you which entries are to be deleted. You can enter the word "all" to delete all matching entries. You can enter a single ID (the number in square brackets) to delete just that single entry. You can enter more than one ID separated by a space to delete multiple entries. Just press [enter] to not delete anything. Note that the interactive delete behavior is a feature of the history function. The history builtin only supports `--exact --case-sensitive` deletion.
- `merge` immediately incorporates history changes from other sessions. Ordinarily `fish` ignores history changes from sessions started after the current one. This command applies those changes immediately.
- `save` immediately writes all changes to the history file. The shell automatically saves the history file; this option is provided for internal use and should not normally need to be used by the user.
- `clear` clears the history file. A prompt is displayed before the history is erased asking you to confirm you really want to clear all history unless `builtin history` is used.

The following options are available:

These flags can appear before or immediately after one of the sub-commands listed above.

- `-C` or `--case-sensitive` does a case-sensitive search. The default is case-insensitive. Note that prior to fish 2.4.0 the default was case-sensitive.
- `-c` or `--contains` searches or deletes items in the history that contain the specified text string. This is the default for the `--search` flag. This is not currently supported by the `--delete` flag.
- `-e` or `--exact` searches or deletes items in the history that exactly match the specified text string. This is the default for the `--delete` flag. Note that the match is case-insensitive by default. If you really want an exact match, including letter case, you must use the `-C` or `--case-sensitive` flag.
- `-p` or `--prefix` searches or deletes items in the history that begin with the specified text string. This is not currently supported by the `--delete` flag.
- `-t` or `--show-time` prepends each history entry with the date and time the entry was recorded . By default it uses the strftime format `# cn`. You can specify another format; e.g., `–show-time='Y-m-d H:M:S '`or`–show-time='aIp'`. The short option,`-t`doesn't accept a stftime format string; it only uses the default format. Any strftime format is allowed, including`s`to get the raw UNIX seconds since the epoch. Note that`–with-time` is also allowed but is deprecated and will be removed at a future date.
- `-z` or `--null` causes history entries written by the search operations to be terminated by a NUL character rather than a newline. This allows the output to be processed by `read -z` to correctly handle multiline history entries.
- `-<number>` `-n <number>` or `--max=<number>` limits the matched history items to the first "n" matching entries. This is only valid for `history search`.
- `-h` or `--help` display help for this command.

## Example

    history clear
    # Deletes all history items

    history search --contains "foo"
    # Outputs a list of all previous commands containing the string "foo".

    history delete --prefix "foo"
    # Interactively deletes commands which start with "foo" from the history.
    # You can select more than one entry by entering their IDs seperated by a space.

## Customizing the name of the history file

By default interactive commands are logged to `$XDG_DATA_HOME/fish/fish_history` (typically `~/.local/share/fish/fish_history`).

You can set the `fish_history` variable to another name for the current shell session. The default value (when the variable is unset) is `fish` which corresponds to `$XDG_DATA_HOME/fish/fish_history`. If you set it to e.g. `fun`, the history would be written to `$XDG_DATA_HOME/fish/fun_history`. An empty string means history will not be stored at all. This is similar to the private session features in web browsers.

You can change `fish_history` at any time (by using `set -x fish_history "session_name"`) and it will take effect right away. If you set it to `"default"`, it will use the default session name (which is `"fish"`).

Other shells such as bash and zsh use a variable named `HISTFILE` for a similar purpose. Fish uses a different name to avoid conflicts and signal that the behavior is different (session name instead of a file path). Also, if you set the var to anything other than `fish` or `default` it will inhibit importing the bash history. That's because the most common use case for this feature is to avoid leaking private or sensitive history when giving a presentation.

## Notes

If you specify both `--prefix` and `--contains` the last flag seen is used.

Note that for backwards compatibility each subcommand can also be specified as a long option. For example, rather than `history search` you can type `history --search`. Those long options are deprecated and will be removed in a future release.

Back to command index.

# if - conditionally execute a command

## Synopsis

    if CONDITION; COMMANDS_TRUE...;
    [else if CONDITION2; COMMANDS_TRUE2...;]
    [else; COMMANDS_FALSE...;]
    end

## Description

`if` will execute the command `CONDITION`. If the condition's exit status is 0, the commands `COMMANDS_TRUE` will execute. If the exit status is not 0 and `else` is given, `COMMANDS_FALSE` will be executed.

You can use `and` or `or` in the condition. See the second example below.

The exit status of the last foreground command to exit can always be accessed using the $status variable.

## Example

The following code will print `foo.txt exists` if the file foo.txt exists and is a regular file, otherwise it will print `bar.txt exists` if the file bar.txt exists and is a regular file, otherwise it will print `foo.txt and bar.txt do not exist`.

    if test -f foo.txt
        echo foo.txt exists
    else if test -f bar.txt
        echo bar.txt exists
    else
        echo foo.txt and bar.txt do not exist
    end

The following code will print "foo.txt exists and is readable" if foo.txt is a regular file and readable

    if test -f foo.txt
       and test -r foo.txt
       echo "foo.txt exists and is readable"
    end

Back to command index.

# isatty - test if a file descriptor is a tty.

## Synopsis

    isatty [FILE DESCRIPTOR]

## Description

`isatty` tests if a file descriptor is a tty.

`FILE DESCRIPTOR` may be either the number of a file descriptor, or one of the strings `stdin`, `stdout`, or `stderr`.

If the specified file descriptor is a tty, the exit status of the command is zero. Otherwise, the exit status is non-zero. No messages are printed to standard error.

## Examples

From an interactive shell, the commands below exit with a return value of zero:

    isatty
    isatty stdout
    isatty 2
    echo | isatty 1

And these will exit non-zero:

    echo | isatty
    isatty 9
    isatty stdout > file
    isatty 2 2> file

Back to command index.

# jobs - print currently running jobs

## Synopsis

    jobs [OPTIONS] [PID]

## Description

`jobs` prints a list of the currently running jobs and their status.

jobs accepts the following switches:

- `-c` or `--command` prints the command name for each process in jobs.
- `-g` or `--group` only prints the group ID of each job.
- `-l` or `--last` prints only the last job to be started.
- `-p` or `--pid` prints the process ID for each process in all jobs.

On systems that supports this feature, jobs will print the CPU usage of each job since the last command was executed. The CPU usage is expressed as a percentage of full CPU activity. Note that on multiprocessor systems, the total activity may be more than 100%.

## Example

`jobs` outputs a summary of the current jobs.

Back to command index.

# math - Perform mathematics calculations

## Synopsis

    math [-sN | --scale=N] [--] EXPRESSION

## Description

`math` is used to perform mathematical calculations. It is a very thin wrapper for the bc program, which makes it possible to specify an expression from the command line without using non-standard extensions or a pipeline.

For a description of the syntax supported by math, see the manual for the bc program. Keep in mind that parameter expansion takes place on any expressions before they are evaluated. This can be very useful in order to perform calculations involving shell variables or the output of command substitutions, but it also means that parenthesis have to be escaped.

The following options are available:

- `-sN` or `--scale=N` sets the scale of the result. `N` must be an integer and defaults to zero. This simply sets bc's `scale` variable to the provided value.

## Return Values

If invalid options or no expression is provided the return `status` is two. If the expression is invalid the return `status` is three. If bc returns a result of `0` (literally, not `0.0` or similar variants) the return `status` is one otherwise it's zero.

## Examples

`math 1+1` outputs 2.

`math $status-128` outputs the numerical exit status of the last command minus 128.

`math 10 / 6` outputs `1`.

`math -s0 10.0 / 6.0` outputs `1`.

`math -s3 10 / 6` outputs `1.666`.

## Cautions

You should always place a `--` flag separator before the expression. 99.99% of the time you'll get the desired result without the separator. Something like `math -10.0 / 2` will fail because the negative floating point value gets treated as an invalid flag. But `math -10 / 2` will work because negative integers are special-cased.

Note that the modulo operator (`x % y`) is not well defined for floating point arithmetic. The `bc` command produces a nonsensical result rather than emit an error and fail in that case. It doesn't matter if the arguments are integers; e.g., `10 % 4`. You'll still get an incorrect result. Do not use the `-sN` flag with N greater than zero if you want sensible answers when using the modulo operator.

Back to command index.

# nextd - move forward through directory history

## Synopsis

    nextd [ -l | --list ] [POS]

## Description

`nextd` moves forwards `POS` positions in the history of visited directories; if the end of the history has been hit, a warning is printed.

If the `-l` or `--list` flag is specified, the current directory history is also displayed.

Note that the `cd` command limits directory history to the 25 most recently visited directories. The history is stored in the `$dirprev` and `$dirnext` variables which this command manipulates.

You may be interested in the `cdh` command which provides a more intuitive way to navigate to recently visited directories.

## Example

    cd /usr/src
    # Working directory is now /usr/src

    cd /usr/src/fish-shell
    # Working directory is now /usr/src/fish-shell

    prevd
    # Working directory is now /usr/src

    nextd
    # Working directory is now /usr/src/fish-shell

Back to command index.

# not - negate the exit status of a job

## Synopsis

    not COMMAND [OPTIONS...]

## Description

`not` negates the exit status of another command. If the exit status is zero, `not` returns 1. Otherwise, `not` returns 0.

## Example

The following code reports an error and exits if no file named spoon can be found.

    if not test -f spoon
        echo There is no spoon
        exit 1
    end

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# open - open file in its default application

## Synopsis

    open FILES...

## Description

`open` opens a file in its default application, using the appropriate tool for the operating system. On GNU/Linux, this requires the common but optional `xdg-open` utility, from the `xdg-utils` package.

Note that this function will not be used if a command by this name exists (which is the case on macOS or Haiku).

## Example

`open *.txt` opens all the text files in the current directory using your system's default text editor.

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# or - conditionally execute a command

## Synopsis

    COMMAND1; or COMMAND2

## Description

`or` is used to execute a command if the current exit status (as set by the previous command) is not 0.

`or` statements may be used as part of the condition in an `and` or `while` block. See the documentation for `if` and `while` for examples.

`or` does not change the current exit status itself, but the command it runs most likely will. The exit status of the last foreground command to exit can always be accessed using the $status variable.

## Example

The following code runs the `make` command to build a program. If the build succeeds, the program is installed. If either step fails, `make clean` is run, which removes the files created by the build process.

    make; and make install; or make clean

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# popd - move through directory stack

## Synopsis

    popd

## Description

`popd` removes the top directory from the directory stack and changes the working directory to the new top directory. Use `pushd` to add directories to the stack.

You may be interested in the `cdh` command which provides a more intuitive way to navigate to recently visited directories.

## Example

    pushd /usr/src
    # Working directory is now /usr/src
    # Directory stack contains /usr/src

    pushd /usr/src/fish-shell
    # Working directory is now /usr/src/fish-shell
    # Directory stack contains /usr/src /usr/src/fish-shell

    popd
    # Working directory is now /usr/src
    # Directory stack contains /usr/src

Back to command index.

# prevd - move backward through directory history

## Synopsis

    prevd [ -l | --list ] [POS]

## Description

`prevd` moves backwards `POS` positions in the history of visited directories; if the beginning of the history has been hit, a warning is printed.

If the `-l` or `--list` flag is specified, the current history is also displayed.

Note that the `cd` command limits directory history to the 25 most recently visited directories. The history is stored in the `$dirprev` and `$dirnext` variables which this command manipulates.

You may be interested in the `cdh` command which provides a more intuitive way to navigate to recently visited directories.

## Example

    cd /usr/src
    # Working directory is now /usr/src

    cd /usr/src/fish-shell
    # Working directory is now /usr/src/fish-shell

    prevd
    # Working directory is now /usr/src

    nextd
    # Working directory is now /usr/src/fish-shell

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# printf - display text according to a format string

## Synopsis

    printf format [argument...]

## Description

printf formats the string FORMAT with ARGUMENT, and displays the result.

The string FORMAT should contain format specifiers, each of which are replaced with successive arguments according to the specifier. Specifiers are detailed below, and are taken from the C library function `printf(3)`.

Unlike `echo`, `printf` does not append a new line unless it is specified as part of the string.

Valid format specifiers are:

- `%d`: Argument will be used as decimal integer (signed or unsigned)
- `%i`: Argument will be used as a signed integer
- `%o`: An octal unsigned integer
- `%u`: An unsigned decimal integer
- `%x` or `%X`: An unsigned hexadecimal integer
- `%f`, `%g` or `%G`: A floating-point number
- `%e` or `%E`: A floating-point number in scientific (XXXeYY) notation
- `%s`: A string
- `%b`: As a string, interpreting backslash escapes, except that octal escapes are of the form \0 or \0ooo.

`%%` signifies a literal "%".

Note that conversion may fail, e.g. "102.234" will not losslessly convert to an integer, causing printf to print an error.

printf also knows a number of backslash escapes:

- `\"` double quote
- `\\` backslash
- `\a` alert (bell)
- `\b` backspace
- `\c` produce no further output
- `\e` escape
- `\f` form feed
- `\n` new line
- `\r` carriage return
- `\t` horizontal tab
- `\v` vertical tab
- `\ooo` octal number (ooo is 1 to 3 digits)
- `\xhh` hexadecimal number (hhh is 1 to 2 digits)
- `\uhhhh` 16-bit Unicode character (hhhh is 4 digits)
- `\Uhhhhhhhh` 32-bit Unicode character (hhhhhhhh is 8 digits)

The `format` argument is re-used as many times as necessary to convert all of the given arguments. If a format specifier is not appropriate for the given argument, an error is printed. For example, `printf 'd' "102.234"` produces an error, as "102.234" cannot be formatted as an integer.

This file has been imported from the printf in GNU Coreutils version 6.9. If you would like to use a newer version of printf, for example the one shipped with your OS, try `command printf`.

## Example

    printf '%s\t%s\n' flounder fish

Will print "flounder fish" (separated with a tab character), followed by a newline character. This is useful for writing completions, as fish expects completion scripts to output the option followed by the description, separated with a tab character.

    printf '%s:%d' "Number of bananas in my pocket" 42

Will print "Number of bananas in my pocket: 42", without a newline.

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# prompt_pwd - Print pwd suitable for prompt

## Synopsis

    prompt_pwd

## Description

prompt_pwd is a function to print the current working directory in a way suitable for prompts. It will replace the home directory with "~" and shorten every path component but the last to a default of one character.

To change the number of characters per path component, set $fish_prompt_pwd_dir_length to the number of characters. Setting it to 0 or an invalid value will disable shortening entirely.

## Examples

    > cd ~/
    > echo $PWD
    /home/alfa

    > prompt_pwd
    ~

    > cd /tmp/banana/sausage/with/mustard
    > prompt_pwd
    /t/b/s/w/mustard

    > set -g fish_prompt_pwd_dir_length 3
    > prompt_pwd
    /tmp/ban/sau/wit/mustard

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# psub - perform process substitution

## Synopsis

    COMMAND1 ( COMMAND2 | psub [-F | --fifo] [-f | --file] [-s SUFFIX])

## Description

Some shells (e.g., ksh, bash) feature a syntax that is a mix between command substitution and piping, called process substitution. It is used to send the output of a command into the calling command, much like command substitution, but with the difference that the output is not sent through commandline arguments but through a named pipe, with the filename of the named pipe sent as an argument to the calling program. `psub` combined with a regular command substitution provides the same functionality.

The following options are available:

- `-f` or `--file` will cause psub to use a regular file instead of a named pipe to communicate with the calling process. This will cause `psub` to be significantly slower when large amounts of data are involved, but has the advantage that the reading process can seek in the stream. This is the default.
- `-F` or `--fifo` will cause psub to use a named pipe rather than a file. You should only use this if the command produces no more than 8 KiB of output. The limit on the amount of data a FIFO can buffer varies with the OS but is typically 8 KiB, 16 KiB or 64 KiB. If you use this option and the command on the left of the psub pipeline produces more output a deadlock is likely to occur.
- `-s` or `--suffix` will append SUFFIX to the filename.

## Example

    diff (sort a.txt | psub) (sort b.txt | psub)
    # shows the difference between the sorted versions of files `a.txt` and `b.txt`.

    source-highlight -f esc (cpp main.c | psub -f -s .c)
    # highlights `main.c` after preprocessing as a C source.

Back to command index.

# pushd - push directory to directory stack

## Synopsis

    pushd [DIRECTORY]

## Description

The `pushd` function adds `DIRECTORY` to the top of the directory stack and makes it the current working directory. `popd` will pop it off and return to the original directory.

Without arguments, it exchanges the top two directories in the stack.

`pushd +NUMBER` rotates the stack counter-clockwise i.e. from bottom to top

`pushd -NUMBER` rotates clockwise i.e. top to bottom.

See also `dirs` and `dirs -c`.

You may be interested in the `cdh` command which provides a more intuitive way to navigate to recently visited directories.

## Example

    pushd /usr/src
    # Working directory is now /usr/src
    # Directory stack contains /usr/src

    pushd /usr/src/fish-shell
    # Working directory is now /usr/src/fish-shell
    # Directory stack contains /usr/src /usr/src/fish-shell

    pushd /tmp/
    # Working directory is now /tmp
    # Directory stack contains /tmp /usr/src /usr/src/fish-shell

    pushd +1
    # Working directory is now /usr/src
    # Directory stack contains /usr/src /usr/src/fish-shell /tmp

    popd
    # Working directory is now /usr/src/fish-shell
    # Directory stack contains /usr/src/fish-shell /tmp

Back to command index.

# pwd - output the current working directory

## Synopsis

    pwd

## Description

`pwd` outputs (prints) the current working directory.

Note that `fish` always resolves symbolic links in the current directory path.

Back to command index.

# random - generate random number

## Synopsis

    random
    random SEED
    random START END
    random START STEP END
    random choice [ITEMS...]

## Description

`RANDOM` generates a pseudo-random integer from a uniform distribution. The range (inclusive) is dependent on the arguments passed. No arguments indicate a range of [0; 32767]. If one argument is specified, the internal engine will be seeded with the argument for future invocations of `RANDOM` and no output will be produced. Two arguments indicate a range of [START; END]. Three arguments indicate a range of [START; END] with a spacing of STEP between possible outputs. `RANDOM choice` will select one random item from the succeeding arguments.

Note that seeding the engine will NOT give the same result across different systems.

You should not consider `RANDOM` cryptographically secure, or even statistically accurate.

## Example

The following code will count down from a random even number between 10 and 20 to 1:

    for i in (seq (random 10 2 20) -1 1)
        echo $i
    end

And this will open a random picture from any of the subdirectories:

    open (random choice **jpg)

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# read - read line of input into variables

## Synopsis

    read [OPTIONS] [VARIABLES...]

## Description

`read` reads from standard input and stores the result in one or more shell variables. By default, one line (terminated by a newline) is read into each variable. Alternatively, a null character or a maximum number of characters can be used to terminate the input. Unlike other shells, there is no default variable (such as `REPLY`) for storing the result.

The following options are available:

- `-c CMD` or `--command=CMD` sets the initial string in the interactive mode command buffer to `CMD`.
- `-g` or `--global` makes the variables global.
- `-i` or `--silent` makes the characters typed obfuscated. This is useful for reading things like passwords or other sensitive information. Note that in bash the short flag is `-s`. We can't use that due to the existing use as an alias for `--shell`.
- `-l` or `--local` makes the variables local.
- `-n NCHARS` or `--nchars=NCHARS` makes `read` return after reading NCHARS characters or the end of the line, whichever comes first.
- `-p PROMPT_CMD` or `--prompt=PROMPT_CMD` uses the output of the shell command `PROMPT_CMD` as the prompt for the interactive mode. The default prompt command is `set_color green; echo read; set_color normal; echo "> "`.
- `-P PROMPT_STR` or `--prompt-str=PROMPT_STR` uses the string as the prompt for the interactive mode. It is equivalent to `echo PROMPT_STR` and is provided solely to avoid the need to frame the prompt as a command. All special characters in the string are automatically escaped before being passed to the `echo` command.
- `-R RIGHT_PROMPT_CMD` or `--right-prompt=RIGHT_PROMPT_CMD` uses the output of the shell command `RIGHT_PROMPT_CMD` as the right prompt for the interactive mode. There is no default right prompt command.
- `-s` or `--shell` enables syntax highlighting, tab completions and command termination suitable for entering shellscript code in the interactive mode.
- `-u` or `--unexport` prevents the variables from being exported to child processes (default behaviour).
- `-U` or `--universal` causes the specified shell variable to be made universal.
- `-x` or `--export` exports the variables to child processes.
- `-a` or `--array` stores the result as an array in a single variable.
- `-z` or `--null` marks the end of the line with the NUL character, instead of newline. This also disables interactive mode.

`read` reads a single line of input from stdin, breaks it into tokens based on the `IFS` shell variable, and then assigns one token to each variable specified in `VARIABLES`. If there are more tokens than variables, the complete remainder is assigned to the last variable. As a special case, if `IFS` is set to the empty string, each character of the input is considered a separate token.

If `-a` or `--array` is provided, only one variable name is allowed and the tokens are stored as an array in this variable.

See the documentation for `set` for more details on the scoping rules for variables.

When `read` reaches the end-of-file (EOF) instead of the terminator, the exit status is set to 1. Otherwise, it is set to 0.

In order to protect the shell from consuming too many system resources, `read` will only consume a maximum of 10 MiB (1048576 bytes); if the terminator is not reached before this limit then VARIABLE is set to empty and the exit status is set to 122. This limit can be altered with the `FISH_READ_BYTE_LIMIT` variable. If set to 0 (zero), the limit is removed.

## Using another read history file

The `read` command supported the `-m` and `--mode-name` flags in fish versions prior to 2.7.0 to specify an alternative read history file. Those flags are now deprecated and ignored. Instead, set the `fish_history` variable to specify a history session ID. That will affect both the `read` history file and the fish command history file. You can set it to an empty string to specify that no history should be read or written. This is useful for presentations where you do not want possibly private or sensitive history to be exposed to the audience but do want history relevant to the presentation to be available.

## Example

The following code stores the value 'hello' in the shell variable `$foo`.

    echo hello|read foo

    # This is a neat way to handle command output by-line:
    printf '%s\n' line1 line2 line3 line4 | while read -l foo
                      echo "This is another line: $foo"
                  end

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# realpath - Convert a path to an absolute path without symlinks

## Synopsis

    realpath path

## Description

This is implemented as a function and a builtin. The function will attempt to use an external realpath command if one can be found. Otherwise it falls back to the builtin. The builtin does not support any options. It's meant to be used only by scripts which need to be portable. The builtin implementation behaves like GNU realpath when invoked without any options (which is the most common use case). In general scripts should not invoke the builtin directly. They should just use `realpath`.

If the path is invalid no translated path will be written to stdout and an error will be reported.

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# return - stop the current inner function

## Synopsis

    function NAME; [COMMANDS...;] return [STATUS]; [COMMANDS...;] end

## Description

`return` halts a currently running function. The exit status is set to `STATUS` if it is given.

It is usually added inside of a conditional block such as an if statement or a switch statement to conditionally stop the executing function and return to the caller, but it can also be used to specify the exit status of a function.

## Example

The following code is an implementation of the false command as a fish function

    function false
        return 1
    end

Back to command index.

# set - display and change shell variables.

## Synopsis

    set [SCOPE_OPTIONS]
    set [OPTIONS] VARIABLE_NAME VALUES...
    set [OPTIONS] VARIABLE_NAME[INDICES]... VALUES...
    set ( -q | --query ) [SCOPE_OPTIONS] VARIABLE_NAMES...
    set ( -e | --erase ) [SCOPE_OPTIONS] VARIABLE_NAME
    set ( -e | --erase ) [SCOPE_OPTIONS] VARIABLE_NAME[INDICES]...
    set ( -S | --show ) [SCOPE_OPTIONS] [VARIABLE_NAME]...

## Description

`set` manipulates shell variables.

If set is called with no arguments, the names and values of all shell variables are printed in sorted order. If some of the scope or export flags have been given, only the variables matching the specified scope are printed.

With both variable names and values provided, `set` assigns the variable `VARIABLE_NAME` the values `VALUES...`.

The following options control variable scope:

- `-l` or `--local` forces the specified shell variable to be given a scope that is local to the current block, even if a variable with the given name exists and is non-local
- `-g` or `--global` causes the specified shell variable to be given a global scope. Non-global variables disappear when the block they belong to ends
- `-U` or `--universal` causes the specified shell variable to be given a universal scope. If this option is supplied, the variable will be shared between all the current users fish instances on the current computer, and will be preserved across restarts of the shell.
- `-x` or `--export` causes the specified shell variable to be exported to child processes (making it an "environment variable")
- `-u` or `--unexport` causes the specified shell variable to NOT be exported to child processes

The following options are available:

- `-e` or `--erase` causes the specified shell variable to be erased
- `-q` or `--query` test if the specified variable names are defined. Does not output anything, but the builtins exit status is the number of variables specified that were not defined.
- `-n` or `--names` List only the names of all defined variables, not their value. The names are guaranteed to be sorted.
- `-S` or `--show` Shows information about the given variables. If no variable names are given then all variables are shown in sorted order. No other flags can be used with this option. The information shown includes whether or not it is set in each of the local, global, and universal scopes. If it is set in one of those scopes whether or not it is exported is reported. The individual elements are also shown along with the length of each element.
- `-L` or `--long` do not abbreviate long values when printing set variables

If a variable is set to more than one value, the variable will be an array with the specified elements. If a variable is set to zero elements, it will become an array with zero elements.

If the variable name is one or more array elements, such as `PATH[1 3 7]`, only those array elements specified will be changed. If you specify a negative index when expanding or assigning to an array variable, the index will be calculated from the end of the array. For example, the index -1 means the last index of an array.

The scoping rules when creating or updating a variable are:

1. If a variable is explicitly set to either universal, global or local, that setting will be honored. If a variable of the same name exists in a different scope, that variable will not be changed.
2. If a variable is not explicitly set to be either universal, global or local, but has been previously defined, the previous variable scope is used.
3. If a variable is not explicitly set to be either universal, global or local and has never before been defined, the variable will be local to the currently executing function. Note that this is different from using the `-l` or `--local` flag. If one of those flags is used, the variable will be local to the most inner currently executing block, while without these the variable will be local to the function. If no function is executing, the variable will be global.

The exporting rules when creating or updating a variable are identical to the scoping rules for variables:

1. If a variable is explicitly set to either be exported or not exported, that setting will be honored.
2. If a variable is not explicitly set to be exported or not exported, but has been previously defined, the previous exporting rule for the variable is kept.
3. If a variable is not explicitly set to be either exported or unexported and has never before been defined, the variable will not be exported.

In query mode, the scope to be examined can be specified.

In erase mode, if variable indices are specified, only the specified slices of the array variable will be erased.

`set` requires all options to come before any other arguments. For example, `set flags -l` will have the effect of setting the value of the variable `flags` to '-l', not making the variable local.

In assignment mode, `set` does not modify the exit status. This allows simultaneous capture of the output and exit status of a subcommand, e.g. `if set output (command)`. In query mode, the exit status is the number of variables that were not found. In erase mode, `set` exits with a zero exit status in case of success, with a non-zero exit status if the commandline was invalid, if the variable was write-protected or if the variable did not exist.

## Example

    set -xg
    # Prints all global, exported variables.

    set foo hi
    # Sets the value of the variable $foo to be 'hi'.

    set -e smurf
    # Removes the variable $smurf

    set PATH[4] ~/bin
    # Changes the fourth element of the $PATH array to ~/bin

    if set python_path (type -p python)
        echo "Python is at $python_path"
    end
    # Outputs the path to Python if `type -p` returns true.

Back to command index.

# set_color - set the terminal color

## Synopsis

    set_color [OPTIONS] VALUE

## Description

`set_color` is used to control the color and styling of text in the terminal. `VALUE` corresponds to a reserved color name such as red or a RGB color value given as 3 or 6 hexadecimal digits. The br-, as in 'bright', forms are full-brightness variants of the 8 standard-brightness colors on many terminals. brblack has higher brightness than black - towards gray. A special keyword normal resets text formatting to terminal defaults.

Valid colors include:

- black, red, green, yellow, blue, magenta, cyan, white
- brblack, brred, brgreen, bryellow, brblue, brmagenta, brcyan, brwhite

An RGB value with three or six hex digits, such as A0FF33 or f2f can be used. `fish` will choose the closest supported color. A three digit value is equivalent to specifying each digit twice; e.g., `set_color 2BC` is the same as `set_color 22BBCC`. Hexadecimal RGB values can be in lower or uppercase. Depending on the capabilities of your terminal (and the level of support `set_color` has for it) the actual color may be approximated by a nearby matching reserved color name or `set_color` may not have an effect on color. A second color may be given as a desired fallback color. e.g. `set_color 124212` brblue will instruct set_color to use brblue if a terminal is not capable of the exact shade of grey desired. This is very useful when an 8 or 16 color terminal might otherwise not use a color.

The following options are available:

- `-b`, `--background` COLOR sets the background color.
- `-c`, `--print-colors` prints a list of the 16 named colors.
- `-o`, `--bold` sets bold mode.
- `-d`, `--dim` sets dim mode.
- `-i`, `--italics` sets italics mode.
- `-r`, `--reverse` sets reverse mode.
- `-u`, `--underline` sets underlined mode.

Using the normal keyword will reset foreground, background, and all formatting back to default.

## Notes

1. Using the normal keyword will reset both background and foreground colors to whatever is the default for the terminal.
2. Setting the background color only affects subsequently written characters. Fish provides no way to set the background color for the entire terminal window. Configuring the window background color (and other attributes such as its opacity) has to be done using whatever mechanisms the terminal provides.
3. Some terminals use the `--bold` escape sequence to switch to a brighter color set rather than increasing the weight of text.
4. `set_color` works by printing sequences of characters to stdout. If used in command substitution or a pipe, these characters will also be captured. This may or may not be desirable. Checking the exit code of `isatty stdout` before using `set_color` can be useful to decide not to colorize output in a script.

## Examples

    set_color red; echo "Roses are red"
    set_color blue; echo "Violets are blue"
    set_color 62A; echo "Eggplants are dark purple"
    set_color normal; echo "Normal is nice" ## Resets the background too

## Terminal Capability Detection

Fish uses a heuristic to decide if a terminal supports the 256-color palette as opposed to the more limited 16 color palette of older terminals. Support can be forced on by setting `fish_term256` to 1. If `$TERM` contains "256color" (e.g., xterm-256color), 256-color support is enabled. If `$TERM` contains xterm, 256 color support is enabled (except for MacOS: `$TERM_PROGRAM` and `$TERM_PROGRAM_VERSION` are used to detect Terminal.app from MacOS 10.6; support is disabled here it because it is known that it reports `xterm` and only supports 16 colors.

If terminfo reports 256 color support for a terminal, support will always be enabled. To debug color palette problems, `tput colors` may be useful to see the number of colors in terminfo for a terminal. Fish launched as `fish -d2` will include diagnostic messages that indicate the color support mode in use.

Many terminals support 24-bit (i.e., true-color) color escape sequences. This includes modern xterm, Gnome Terminal, Konsole, and iTerm2. Fish attempts to detect such terminals through various means in `config.fish` You can explicitly force that support via `set fish_term24bit 1`.

The `set_color` command uses the terminfo database to look up how to change terminal colors on whatever terminal is in use. Some systems have old and incomplete terminfo databases, and may lack color information for terminals that support it. Fish will assume that all terminals can use the ANSI X3.64 escape sequences if the terminfo definition indicates a color below 16 is not supported.

Support for italics, dim, reverse, and other modes is not guaranteed in all terminal emulators. Fish attempts to determine if the terminal supports these modes even if the terminfo database may not be up-to-date.

Back to command index.

# source - evaluate contents of file.

## Synopsis

    source FILENAME [ARGUMENTS...]

## Description

`source` evaluates the commands of the specified file in the current shell. This is different from starting a new process to perform the commands (i.e. `fish < FILENAME`) since the commands will be evaluated by the current shell, which means that changes in shell variables will affect the current shell. If additional arguments are specified after the file name, they will be inserted into the `$argv` variable. The `$argv` variable will not include the name of the sourced file.

If no file is specified, or if the file name '`-`' is used, stdin will be read.

The return status of `source` is the return status of the last job to execute. If something goes wrong while opening or reading the file, `source` exits with a non-zero status.

`.` (a single period) is an alias for the `source` command. The use of `.` is deprecated in favour of `source`, and `.` will be removed in a future version of fish.

## Example

    source ~/.config/fish/config.fish
    # Causes fish to re-read its initialization file.

## Caveats

In fish versions prior to 2.3.0 the `$argv` variable would have a single element (the name of the sourced file) if no arguments are present. Otherwise it would contain arguments without the name of the sourced file. That behavior was very confusing and unlike other shells such as bash and zsh.

Back to command index.

# status - query fish runtime information

## Synopsis

    status
    status is-login
    status is-interactive
    status is-block
    status is-breakpoint
    status is-command-substitution
    status is-no-job-control
    status is-full-job-control
    status is-interactive-job-control
    status filename
    status function
    status line-number
    status stack-trace
    status job-control CONTROL-TYPE

## Description

With no arguments, `status` displays a summary of the current login and job control status of the shell.

The following operations (sub-commands) are available:

- `is-command-sub` returns 0 if fish is currently executing a command substitution. Also `-c` or `--is-command-substitution`.
- `is-block` returns 0 if fish is currently executing a block of code. Also `-b` or `--is-block`.
- `is-breakpoint` returns 0 if fish is currently showing a prompt in the context of a `breakpoint` command. See also the `fish_breakpoint_prompt` function.
- `is-interactive` returns 0 if fish is interactive - that is, connected to a keyboard. Also `-i` or `--is-interactive`.
- `is-login` returns 0 if fish is a login shell - that is, if fish should perform login tasks such as setting up the PATH. Also `-l` or `--is-login`.
- `is-full-job-control` returns 0 if full job control is enabled. Also `--is-full-job-control` (no short flag).
- `is-interactive-job-control` returns 0 if interactive job control is enabled. Also, `--is-interactive-job-control` (no short flag).
- `is-no-job-control` returns 0 if no job control is enabled. Also `--is-no-job-control` (no short flag).
- `filename` prints the filename of the currently running script. Also `current-filename`, `-f` or `--current-filename`.
- `function` prints the name of the currently called function if able, when missing displays "Not a function" (or equivalent translated string). Also `current-function`, `-u` or `--current-function`.
- `line-number` prints the line number of the currently running script. Also `current-line-number`, `-n` or `--current-line-number`.
- `job-control CONTROL-TYPE` sets the job control type, which can be `none`, `full`, or `interactive`. Also `-j CONTROL-TYPE` or `--job-control=CONTROL-TYPE`.
- `stack-trace` prints a stack trace of all function calls on the call stack. Also `print-stack-trace`, `-t` or `--print-stack-trace`.

## Notes

For backwards compatibility each subcommand can also be specified as a long or short option. For example, rather than `status is-login` you can type `status --is-login`. The flag forms are deprecated and may be removed in a future release (but not before fish 3.0).

You can only specify one subcommand per invocation even if you use the flag form of the subcommand.

Back to command index.

# string - manipulate strings

## Synopsis

    string escape [(-n | --no-quoted)] [--style=xxx] [STRING...]
    string join [(-q | --quiet)] SEP [STRING...]
    string length [(-q | --quiet)] [STRING...]
    string lower [(-q | --quiet)] [STRING...]
    string match [(-a | --all)] [((-e | --entire)] [(-i | --ignore-case)] [(-r | --regex)]
                 [(-n | --index)] [(-q | --quiet)] [(-v | --invert)] PATTERN [STRING...]
    string repeat [(-n | --count) COUNT] [(-m | --max) MAX] [(-N | --no-newline)]
                  [(-q | --quiet)] [STRING...]
    string replace [(-a | --all)] [(-f | --filter)] [(-i | --ignore-case)] [(-r | --regex)]
                   [(-q | --quiet)] PATTERN REPLACEMENT [STRING...]
    string split [(-m | --max) MAX] [(-r | --right)] [(-q | --quiet)] SEP
                 [STRING...]
    string sub [(-s | --start) START] [(-l | --length) LENGTH] [(-q | --quiet)]
               [STRING...]
    string trim [(-l | --left)] [(-r | --right)] [(-c | --chars CHARS)]
                [(-q | --quiet)] [STRING...]
    string unescape [--style=xxx] [STRING...]
    string upper [(-q | --quiet)] [STRING...]

## Description

`string` performs operations on strings.

STRING arguments are taken from the command line unless standard input is connected to a pipe or a file, in which case they are read from standard input, one STRING per line. It is an error to supply STRING arguments on the command line and on standard input.

Arguments beginning with `-` are normally interpreted as switches; `--` causes the following arguments not to be treated as switches even if they begin with `-`. Switches and required arguments are recognized only on the command line.

Most subcommands accept a `-q` or `--quiet` switch, which suppresses the usual output but exits with the documented status.

The following subcommands are available.

## "escape" subcommand

`string escape` escapes each STRING in one of three ways. The first is `--style=script`. This is the default. It alters the string such that it can be passed back to `eval` to produce the original argument again. By default, all special characters are escaped, and quotes are used to simplify the output when possible. If `-n` or `--no-quoted` is given, the simplifying quoted format is not used. Exit status: 0 if at least one string was escaped, or 1 otherwise.

The second is `--style=var` which ensures the string can be used as a variable name by hex encoding any non-alphanumeric characters. The string is first converted to UTF-8 before being encoded.

The third is `--style=url` which ensures the string can be used as a URL by hex encoding any character which is not legal in a URL. The string is first converted to UTF-8 before being encoded.

`string unescape` performs the inverse of the `string escape` command. If the string to be unescaped is not properly formatted it is ignored. For example, doing `string unescape --style=var (string escape --style=var $str)` will return the original string.

## "join" subcommand

`string join` joins its STRING arguments into a single string separated by SEP, which can be an empty string. Exit status: 0 if at least one join was performed, or 1 otherwise.

## "length" subcommand

`string length` reports the length of each string argument in characters. Exit status: 0 if at least one non-empty STRING was given, or 1 otherwise.

## "lower" subcommand

`string lower` converts each string argument to lowercase. Exit status: 0 if at least one string was converted to lowercase, else 1. This means that in conjunction with the `-q` flag you can readily test whether a string is already lowercase.

## "match" subcommand

`string match` tests each STRING against PATTERN and prints matching substrings. Only the first match for each STRING is reported unless `-a` or `--all` is given, in which case all matches are reported.

If you specify the `-e` or `--entire` then each matching string is printed including any prefix or suffix not matched by the pattern (equivalent to `grep` without the `-o` flag). You can, obviously, achieve the same result by prepending and appending `*` or `.*` depending on whether or not you have specified the `--regex` flag. The `--entire` flag is simply a way to avoid having to complicate the pattern in that fashion and make the intent of the `string match` clearer. Without `--entire` and `--regex`, a PATTERN will need to match the entire STRING before it will be reported.

Matching can be made case-insensitive with `--ignore-case` or `-i`.

If `--index` or `-n` is given, each match is reported as a 1-based start position and a length. By default, PATTERN is interpreted as a glob pattern matched against each entire STRING argument. A glob pattern is only considered a valid match if it matches the entire STRING.

If `--regex` or `-r` is given, PATTERN is interpreted as a Perl-compatible regular expression, which does not have to match the entire STRING. For a regular expression containing capturing groups, multiple items will be reported for each match, one for the entire match and one for each capturing group. With this, only the matching part of the STRING will be reported, unless `--entire` is given.

If `--invert` or `-v` is used the selected lines will be only those which do not match the given glob pattern or regular expression.

Exit status: 0 if at least one match was found, or 1 otherwise.

## "repeat" subcommand

`string repeat` repeats the STRING `-n` or `--count` times. The `-m` or `--max` option will limit the number of outputed char (excluding the newline). This option can be used by itself or in conjuction with `--count`. If both `--count` and `--max` are present, max char will be outputed unless the final repeated string size is less than max, in that case, the string will repeat until count has been reached. Both `--count` and `--max` will accept a number greater than or equal to zero, in the case of zero, nothing will be outputed. If `-N` or `--no-newline` is given, the output won't contain a newline character at the end. Exit status: 0 if yielded string is not empty, 1 otherwise.

## "replace" subcommand

`string replace` is similar to `string match` but replaces non-overlapping matching substrings with a replacement string and prints the result. By default, PATTERN is treated as a literal substring to be matched.

If `-r` or `--regex` is given, PATTERN is interpreted as a Perl-compatible regular expression, and REPLACEMENT can contain C-style escape sequences like `\t` as well as references to capturing groups by number or name as `$n` or `${n}`.

If you specify the `-f` or `--filter` flag then each input string is printed only if a replacement was done. This is useful where you would otherwise use this idiom: `a_cmd | string match pattern | string replace pattern new_pattern`. You can instead just write `a_cmd | string replace --filter pattern new_pattern`.

Exit status: 0 if at least one replacement was performed, or 1 otherwise.

## "split" subcommand

`string split` splits each STRING on the separator SEP, which can be an empty string. If `-m` or `--max` is specified, at most MAX splits are done on each STRING. If `-r` or `--right` is given, splitting is performed right-to-left. This is useful in combination with `-m` or `--max`. Exit status: 0 if at least one split was performed, or 1 otherwise.

## "sub" subcommand

`string sub` prints a substring of each string argument. The start of the substring can be specified with `-s` or `--start` followed by a 1-based index value. Positive index values are relative to the start of the string and negative index values are relative to the end of the string. The default start value is 1. The length of the substring can be specified with `-l` or `--length`. If the length is not specified, the substring continues to the end of each STRING. Exit status: 0 if at least one substring operation was performed, 1 otherwise.

## "trim" subcommand

`string trim` removes leading and trailing whitespace from each STRING. If `-l` or `--left` is given, only leading whitespace is removed. If `-r` or `--right` is given, only trailing whitespace is trimmed. The `-c` or `--chars` switch causes the characters in CHARS to be removed instead of whitespace. Exit status: 0 if at least one character was trimmed, or 1 otherwise.

## "upper" subcommand

`string upper` converts each string argument to uppercase. Exit status: 0 if at least one string was converted to uppercase, else 1. This means that in conjunction with the `-q` flag you can readily test whether a string is already uppercase.

## Regular Expressions

Both the `match` and `replace` subcommand support regular expressions when used with the `-r` or `--regex` option. The dialect is that of PCRE2.

In general, special characters are special by default, so `a+` matches one or more "a"s, while `a\+` matches an "a" and then a "+". `(a+)` matches one or more "a"s in a capturing group (`(?:XXXX)` denotes a non-capturing group). For the replacement parameter of `replace`, `$n` refers to the n-th group of the match. In the match parameter, `\n` (e.g. `\1`) refers back to groups.

## Examples

    > string length 'hello, world'
    12

    > set str foo
    > string length -q $str; echo $status
    0
    # Equivalent to test -n $str

    > string sub --length 2 abcde
    ab

    > string sub -s 2 -l 2 abcde
    bc

    > string sub --start=-2 abcde
    de

    > string split . example.com
    example
    com

    > string split -r -m1 / /usr/local/bin/fish
    /usr/local/bin
    fish

    > string split '' abc
    a
    b
    c

    > seq 3 | string join ...
    1...2...3

    > string trim ' abc  '
    abc

    > string trim --right --chars=yz xyzzy zany
    x
    zan

    > echo \x07 | string escape
    \cg

    > string escape --style=var 'a1 b2'\\u6161
    \a1_20b2__c_E6_85_A1

## Match Glob Examples

    > string match '?' a
    a

    > string match 'a*b' axxb
    axxb

    > string match -i 'a??B' Axxb
    Axxb

    > echo 'ok?' | string match '*\?'
    ok?

    # Note that only the second STRING will match here.
    > string match 'foo' 'foo1' 'foo' 'foo2'
    foo

    > string match -e 'foo' 'foo1' 'foo' 'foo2'
    foo1
    foo
    foo2

    > string match 'foo?' 'foo1' 'foo' 'foo2'
    foo1
    foo
    foo2

## Match Regex Examples

    > string match -r 'cat|dog|fish' 'nice dog'
    dog

    > string match -r -v "c.*[12]" {cat,dog}(seq 1 4)
    dog1
    dog2
    cat3
    dog3
    cat4
    dog4

    > string match -r '(\d\d?):(\d\d):(\d\d)' 2:34:56
    2:34:56
    2
    34
    56

    > string match -r '^(\w{2,4})\g1$' papa mud murmur
    papa
    pa
    murmur
    mur

    > string match -r -a -n at ratatat
    2 2
    4 2
    6 2

    > string match -r -i '0x[0-9a-f]{1,8}' 'int magic = 0xBadC0de;'
    0xBadC0de

## Replace Literal Examples

    > string replace is was 'blue is my favorite'
    blue was my favorite

    > string replace 3rd last 1st 2nd 3rd
    1st
    2nd
    last

    > string replace -a ' ' _ 'spaces to underscores'
    spaces_to_underscores

## Replace Regex Examples

    > string replace -r -a '[^\d.]+' ' ' '0 one two 3.14 four 5x'
    0 3.14 5

    > string replace -r '(\w+)\s+(\w+)' '$2 $1 $$' 'left right'
    right left $

    > string replace -r '\s*newline\s*' '\n' 'put a newline here'
    put a
    here

## Repeat Examples

    > string repeat -n 2 'foo '
    foo foo

    > echo foo | string repeat -n 2
    foofoo

    > string repeat -n 2 -m 5 'foo'
    foofo

    > string repeat -m 5 'foo'
    foofo

Back to command index.

# suspend - suspend the current shell

## Synopsis

    suspend [--force]

## Description

`suspend` suspends execution of the current shell by sending it a SIGTSTP signal, returning to the controlling process. It can be resumed later by sending it a SIGCONT. In order to prevent suspending a shell that doesn't have a controlling process, it will not suspend the shell if it is a login shell. This requirement is bypassed if the `--force` option is given or the shell is not interactive.

Back to command index.

# switch - conditionally execute a block of commands

## Synopsis

    switch VALUE; [case [WILDCARD...]; [COMMANDS...]; ...] end

## Description

`switch` performs one of several blocks of commands, depending on whether a specified value equals one of several wildcarded values. `case` is used together with the `switch` statement in order to determine which block should be executed.

Each `case` command is given one or more parameters. The first `case` command with a parameter that matches the string specified in the switch command will be evaluated. `case` parameters may contain wildcards. These need to be escaped or quoted in order to avoid regular wildcard expansion using filenames.

Note that fish does not fall through on case statements. Only the first matching case is executed.

Note that command substitutions in a case statement will be evaluated even if its body is not taken. All substitutions, including command substitutions, must be performed before the value can be compared against the parameter.

## Example

If the variable $animal contains the name of an animal, the following code would attempt to classify it:

    switch $animal
        case cat
            echo evil
        case wolf dog human moose dolphin whale
            echo mammal
        case duck goose albatross
            echo bird
        case shark trout stingray
            echo fish
        case '*'
            echo I have no idea what a $animal is
    end

If the above code was run with `$animal` set to `whale`, the output would be `mammal`.

Back to command index.

# test - perform tests on files and text

## Synopsis

    test [EXPRESSION]
    [ [EXPRESSION] ]

## Description

Tests the expression given and sets the exit status to 0 if true, and 1 if false. An expression is made up of one or more operators and their arguments.

The first form (`test`) is preferred. For compatibility with other shells, the second form is available: a matching pair of square brackets (`[ [EXPRESSION ] ]`).

This test is mostly POSIX-compatible.

When using a variable as an argument for a test operator you should almost always enclose it in double-quotes. There are only two situations it is safe to omit the quote marks. The first is when the argument is a literal string with no whitespace or other characters special to the shell (e.g., semicolon). For example, `test -b /my/file`. The second is using a variable that expands to exactly one element including if that element is the empty string (e.g., `set x ''`). If the variable is not set, set but with no value, or set to more than one value you must enclose it in double-quotes. For example,`test "$x" = "$y"`. Since it is always safe to enclose variables in double-quotes when used as`test` arguments that is the recommended practice.

## Operators for files and directories

- `-b FILE` returns true if `FILE` is a block device.
- `-c FILE` returns true if `FILE` is a character device.
- `-d FILE` returns true if `FILE` is a directory.
- `-e FILE` returns true if `FILE` exists.
- `-f FILE` returns true if `FILE` is a regular file.
- `-g FILE` returns true if `FILE` has the set-group-ID bit set.
- `-G FILE` returns true if `FILE` exists and has the same group ID as the current user.
- `-k FILE` returns true if `FILE` has the sticky bit set. If the OS does not support the concept it returns false. See https://en.wikipedia.org/wiki/Sticky_bit.
- `-L FILE` returns true if `FILE` is a symbolic link.
- `-O FILE` returns true if `FILE` exists and is owned by the current user.
- `-p FILE` returns true if `FILE` is a named pipe.
- `-r FILE` returns true if `FILE` is marked as readable.
- `-s FILE` returns true if the size of `FILE` is greater than zero.
- `-S FILE` returns true if `FILE` is a socket.
- `-t FD` returns true if the file descriptor `FD` is a terminal (TTY).
- `-u FILE` returns true if `FILE` has the set-user-ID bit set.
- `-w FILE` returns true if `FILE` is marked as writable; note that this does not check if the filesystem is read-only.
- `-x FILE` returns true if `FILE` is marked as executable.

## Operators for text strings

- `STRING1 = STRING2` returns true if the strings `STRING1` and `STRING2` are identical.
- `STRING1 != STRING2` returns true if the strings `STRING1` and `STRING2` are not identical.
- `-n STRING` returns true if the length of `STRING` is non-zero.
- `-z STRING` returns true if the length of `STRING` is zero.

## Operators to compare and examine numbers

- `NUM1 -eq NUM2` returns true if `NUM1` and `NUM2` are numerically equal.
- `NUM1 -ne NUM2` returns true if `NUM1` and `NUM2` are not numerically equal.
- `NUM1 -gt NUM2` returns true if `NUM1` is greater than `NUM2`.
- `NUM1 -ge NUM2` returns true if `NUM1` is greater than or equal to `NUM2`.
- `NUM1 -lt NUM2` returns true if `NUM1` is less than `NUM2`.
- `NUM1 -le NUM2` returns true if `NUM1` is less than or equal to `NUM2`.

Note that only integers are supported. For more complex mathematical operations, including fractions, the `env` program may be useful. Consult the documentation for your operating system.

## Operators to combine expressions

- `COND1 -a COND2` returns true if both `COND1` and `COND2` are true.
- `COND1 -o COND2` returns true if either `COND1` or `COND2` are true.

Expressions can be inverted using the `!` operator:

- `! EXPRESSION` returns true if `EXPRESSION` is false, and false if `EXPRESSION` is true.

Expressions can be grouped using parentheses.

- `( EXPRESSION )` returns the value of `EXPRESSION`.

  Note that parentheses will usually require escaping with `\(` to avoid being interpreted as a command substitution.

## Examples

If the `/tmp` directory exists, copy the `/etc/motd` file to it:

    if test -d /tmp
        cp /etc/motd /tmp/motd
    end

If the variable `MANPATH` is defined and not empty, print the contents. (If `MANPATH` is not defined, then it will expand to zero arguments, unless quoted.)

    if test -n "$MANPATH"
        echo $MANPATH
    end

Parentheses and the `-o` and `-a` operators can be combined to produce more complicated expressions. In this example, success is printed if there is a `/foo` or `/bar` file as well as a `/baz` or `/bat` file.

    if test \( -f /foo -o -f /bar \) -a \( -f /baz -o -f /bat \)
        echo Success.
    end.

Numerical comparisons will simply fail if one of the operands is not a number:

    if test 42 -eq "The answer to life, the universe and everything"
        echo So long and thanks for all the fish ## will not be executed
    end

A common comparison is with $status:

    if test $status -eq 0
        echo "Previous command succeeded"
    end

The previous test can likewise be inverted:

    if test ! $status -eq 0
        echo "Previous command failed"
    end

which is logically equivalent to the following:

    if test $status -ne 0
        echo "Previous command failed"
    end

## Standards

`test` implements a subset of the IEEE Std 1003.1-2008 (POSIX.1) standard. The following exceptions apply:

- The `<` and `>` operators for comparing strings are not implemented.

- Because this test is a shell builtin and not a standalone utility, using the -c flag on a special file descriptors like standard input and output may not return the same result when invoked from within a pipe as one would expect when invoking the `test` utility in another shell.

  In cases such as this, one can use `command` `test` to explicitly use the system's standalone `test` rather than this `builtin` `test`.

Back to command index.

# trap - perform an action when the shell receives a signal

## Synopsis

    trap [OPTIONS] [[ARG] REASON ... ]

## Description

`trap` is a wrapper around the fish event delivery framework. It exists for backwards compatibility with POSIX shells. For other uses, it is recommended to define an event handler.

The following parameters are available:

- `ARG` is the command to be executed on signal delivery.
- `REASON` is the name of the event to trap. For example, a signal like `INT` or `SIGINT`, or the special symbol `EXIT`.
- `-l` or `--list-signals` prints a list of signal names.
- `-p` or `--print` prints all defined signal handlers.

If `ARG` and `REASON` are both specified, `ARG` is the command to be executed when the event specified by `REASON` occurs (e.g., the signal is delivered).

If `ARG` is absent (and there is a single REASON) or -, each specified signal is reset to its original disposition (the value it had upon entrance to the shell). If `ARG` is the null string the signal specified by each `REASON` is ignored by the shell and by the commands it invokes.

If `ARG` is not present and `-p` has been supplied, then the trap commands associated with each `REASON` are displayed. If no arguments are supplied or if only `-p` is given, `trap` prints the list of commands associated with each signal.

Signal names are case insensitive and the `SIG` prefix is optional.

The return status is 1 if any `REASON` is invalid; otherwise trap returns 0.

## Example

    trap "status --print-stack-trace" SIGUSR1
    # Prints a stack trace each time the SIGUSR1 signal is sent to the shell.

Back to command index.

# true - return a successful result

## Synopsis

    true

## Description

`true` sets the exit status to 0.

Back to command index.

# type - indicate how a command would be interpreted

## Synopsis

    type [OPTIONS] NAME [NAME ...]

## Description

With no options, `type` indicates how each `NAME` would be interpreted if used as a command name.

The following options are available:

- `-a` or `--all` prints all of possible definitions of the specified names.
- `-f` or `--no-functions` suppresses function and builtin lookup.
- `-t` or `--type` prints `function`, `builtin`, or `file` if `NAME` is a shell function, builtin, or disk file, respectively.
- `-p` or `--path` returns the name of the disk file that would be executed, or nothing if `type -t name` would not return `file`.
- `-P` or `--force-path` returns the name of the disk file that would be executed, or nothing if no file with the specified name could be found in the `$PATH`.
- `-q` or `--quiet` suppresses all output; this is useful when testing the exit status.

The `-q`, `-p`, `-t` and `-P` flags (and their long flag aliases) are mutually exclusive. Only one can be specified at a time.

## Example

    > type fg
    fg is a builtin

Back to command index.

# ulimit - set or get resource usage limits

## Synopsis

    ulimit [OPTIONS] [LIMIT]

## Description

`ulimit` builtin sets or outputs the resource usage limits of the shell and any processes spawned by it. If a new limit value is omitted, the current value of the limit of the resource is printed; otherwise, the specified limit is set to the new value.

Use one of the following switches to specify which resource limit to set or report:

- `-c` or `--core-size`: the maximum size of core files created. By setting this limit to zero, core dumps can be disabled.
- `-d` or `--data-size`: the maximum size of a process' data segment.
- `-f` or `--file-size`: the maximum size of files created by the shell.
- `-l` or `--lock-size`: the maximum size that may be locked into memory.
- `-m` or `--resident-set-size`: the maximum resident set size.
- `-n` or `--file-descriptor-count`: the maximum number of open file descriptors (most systems do not allow this value to be set).
- `-s` or `--stack-size`: the maximum stack size.
- `-t` or `--cpu-time`: the maximum amount of CPU time in seconds.
- `-u` or `--process-count`: the maximum number of processes available to a single user.
- `-v` or `--virtual-memory-size` The maximum amount of virtual memory available to the shell.

Note that not all these limits are available in all operating systems.

The value of limit can be a number in the unit specified for the resource or one of the special values `hard`, `soft`, or `unlimited`, which stand for the current hard limit, the current soft limit, and no limit, respectively.

If limit is given, it is the new value of the specified resource. If no option is given, then `-f` is assumed. Values are in kilobytes, except for `-t`, which is in seconds and `-n` and `-u`, which are unscaled values. The return status is 0 unless an invalid option or argument is supplied, or an error occurs while setting a new limit.

`ulimit` also accepts the following switches that determine what type of limit to set:

- `-H` or `--hard` sets hard resource limit
- `-S` or `--soft` sets soft resource limit

A hard limit can only be decreased. Once it is set it cannot be increased; a soft limit may be increased up to the value of the hard limit. If neither -H nor -S is specified, both the soft and hard limits are updated when assigning a new limit value, and the soft limit is used when reporting the current value.

The following additional options are also understood by `ulimit`:

- `-a` or `--all` prints all current limits

The `fish` implementation of `ulimit` should behave identically to the implementation in bash, except for these differences:

- Fish `ulimit` supports GNU-style long options for all switches
- Fish `ulimit` does not support the `-p` option for getting the pipe size. The bash implementation consists of a compile-time check that empirically guesses this number by writing to a pipe and waiting for SIGPIPE. Fish does not do this because it this method of determining pipe size is unreliable. Depending on bash version, there may also be further additional limits to set in bash that do not exist in fish.
- Fish `ulimit` does not support getting or setting multiple limits in one command, except reporting all values using the -a switch

## Example

`ulimit -Hs 64` sets the hard stack size limit to 64 kB.

Back to command index.

# umask - set or get the file creation mode mask

## Synopsis

    umask [OPTIONS] [MASK]

## Description

`umask` displays and manipulates the "umask", or file creation mode mask, which is used to restrict the default access to files.

The umask may be expressed either as an octal number, which represents the rights that will be removed by default, or symbolically, which represents the only rights that will be granted by default.

Access rights are explained in the manual page for the `chmod`(1) program.

With no parameters, the current file creation mode mask is printed as an octal number.

- `-h` or `--help` prints this message.
- `-S` or `--symbolic` prints the umask in symbolic form instead of octal form.
- `-p` or `--as-command` outputs the umask in a form that may be reused as input

If a numeric mask is specified as a parameter, the current shell's umask will be set to that value, and the rights specified by that mask will be removed from new files and directories by default.

If a symbolic mask is specified, the desired permission bits, and not the inverse, should be specified. A symbolic mask is a comma separated list of rights. Each right consists of three parts:

- The first part specifies to whom this set of right applies, and can be one of `u`, `g`, `o` or `a`, where `u` specifies the user who owns the file, `g` specifies the group owner of the file, `o` specific other users rights and `a` specifies all three should be changed.
- The second part of a right specifies the mode, and can be one of `=`, `+` or `-`, where `=` specifies that the rights should be set to the new value, `+` specifies that the specified right should be added to those previously specified and `-` specifies that the specified rights should be removed from those previously specified.
- The third part of a right specifies what rights should be changed and can be any combination of `r`, `w` and `x`, representing read, write and execute rights.

If the first and second parts are skipped, they are assumed to be `a` and `=`, respectively. As an example, `r,u+w` means all users should have read access and the file owner should also have write access.

Note that symbolic masks currently do not work as intended.

## Example

`umask 177` or `umask u=rw` sets the file creation mask to read and write for the owner and no permissions at all for any other users.

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# vared - interactively edit the value of an environment variable

## Synopsis

    vared VARIABLE_NAME

## Description

`vared` is used to interactively edit the value of an environment variable. Array variables as a whole can not be edited using `vared`, but individual array elements can.

## Example

`vared PATH[3]` edits the third element of the PATH array

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# while - perform a command multiple times

## Synopsis

    while CONDITION; COMMANDS...; end

## Description

`while` repeatedly executes `CONDITION`, and if the exit status is 0, then executes `COMMANDS`.

If the exit status of `CONDITION` is non-zero on the first iteration, `COMMANDS` will not be executed at all.

You can use `and` or `or` for complex conditions. Even more complex control can be achieved with `while true` containing a break.

## Example

    while test -f foo.txt; or test -f bar.txt ; echo file exists; sleep 10; end
    # outputs 'file exists' at 10 second intervals as long as the file foo.txt or bar.txt exists.

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