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Catalog / Fish Shell Cheatsheet

Fish Shell Cheatsheet

A comprehensive cheat sheet covering essential Fish shell commands, syntax, and configurations for improved productivity and customization.

Basics & Navigation

Shell Navigation

cd directory_name

Change directory to directory_name.

cd ..

Move one directory up.

cd -

Return to the previous directory.

pwd

Print the current working directory.

ls

List files and directories in the current directory.

ls -l

List files with detailed information (permissions, size, etc.).

ls -a

List all files, including hidden files.

Basic Commands

echo 'text'

Prints the specified text to the terminal.

printf '%s\n' 'text'

Prints the specified text with a trailing newline.

read my_variable

Reads input from stdin and assigns it to my_variable.

clear

Clears the terminal screen.

history

Displays the command history.

Keybindings

Ctrl+A

Move cursor to the beginning of the line.

Ctrl+E

Move cursor to the end of the line.

Alt+Left

Jump to the previous word.

Alt+Right

Jump to the next word.

Up/Down Arrows

Switch to the previous/next command in history.

Alt+Up/Down

Switch to the previous/next arguments.

Ctrl+U

Delete from cursor to the beginning of the line.

Ctrl+C

Cancel the current command.

Variables & Loops

Variable Management

set my_variable 'value'

Sets a variable named my_variable to ‘value’.

set -g my_variable 'value'

Sets a global variable accessible in all scopes.

set -l my_variable 'value'

Sets a local variable, only accessible within the current scope.

set --erase my_variable

Removes the variable my_variable.

echo $my_variable

Prints the value of my_variable.

echo $my_variable[1..3]

Prints a slice of the variable (characters 1 to 3).

Loop Structures

for i in item1 item2 item3; ...; end

Iterates over a list of items.

for i in (seq 1 5); ...; end

Iterates over a sequence of numbers from 1 to 5.

while condition; ...; end

Executes a block of code as long as the condition is true.

break

Exits the current loop.

continue

Skips the current iteration and continues with the next.

Arithmetic Operations

math 1 + 2

Performs addition.

math 5 - 3

Performs subtraction.

math 4 \* 6

Performs multiplication.

math 8 / 2

Performs division.

math 7 % 3

Calculates the modulo (remainder).

math 2 ^ 3

Performs exponentiation.

set counter (math $counter + 1)

Increments a variable counter by 1.

Conditionals & Strings

Conditional Statements

if condition; ...; end

Executes a block of code if the condition is true.

else

Executes a block of code if the previous if condition is false.

else if condition; ...; end

Chains another condition to check if the initial if is false.

test condition

Evaluates a condition; returns 0 if true, 1 if false.

and

Logical AND operator for combining conditions.

or

Logical OR operator for combining conditions.

not

Logical NOT operator to negate a condition.

String Manipulation

string length 'text'

Returns the length of the string ‘text’.

string sub --start 2 --length 3 'example'

Extracts a substring of length 3 starting from index 2.

string match --regex 'pattern' 'string'

Matches a string against a regular expression; returns the match or nothing.

string replace --all 'old' 'new' 'string'

Replaces all occurrences of ‘old’ with ‘new’ in ‘string’.

string join 'separator' item1 item2 ...

Joins items together with the specified separator.

string split 'separator' 'string'

Splits a string into an array based on the separator.

String Matching Patterns

x?

Matches zero or one occurrences of x.

x*

Matches zero or more occurrences of x.

x+

Matches one or more occurrences of x.

x{n}

Matches exactly n occurrences of x.

x{n,m}

Matches between n and m occurrences of x.

[xy]

Matches either x or y.

[^xy]

Matches any character that is not x or y.

Functions & Events

Function Definition

function my_function; ...; end

Defines a new function named my_function.

function my_function -a argument1 argument2; ...; end

Defines a function accepting specific arguments.

function my_function -d 'description'; ...; end

Adds a description to the function.

functions --erase my_function

Removes the function my_function.

return

Exits the function, optionally returning a value.

$argv

Array containing the arguments passed to the function.

Event Handling

emit my_event

Emits an event named my_event.

function hook_function --on-event my_event; ...; end

Defines a hook function that runs when my_event is emitted.

function hook_function --on-variable my_variable; ...; end

Defines a hook function that runs when my_variable is changed.

function hook_function --on-signal SIGINT; ...; end

Defines a hook function that runs when the SIGINT signal is received (e.g., Ctrl+C).

Process Communication

> file

Redirects the output to a file, overwriting its contents.

>> file

Appends the output to a file.

| command

Pipes the output to another command.

(command)

Command substitution; replaces the command with its output.

(command | psub)

Process substitution; creates a temporary file with the output of the command.

Abbreviations & Completions

Abbreviations

abbr --add short_cmd 'long command'

Adds an abbreviation; typing short_cmd will execute long command.

abbr --erase short_cmd

Removes the abbreviation short_cmd.

abbr

Lists all defined abbreviations.

Example:

abbr --add gcm 'git commit -m'

Creates an abbreviation for git commit -m. Use: gcm 'Your commit message'

Command Completions

complete --command cmd --arguments arg1 arg2

Adds completions for the command cmd with specified arguments.

complete --command cmd --erase

Removes all completions for the command cmd.

complete --command cmd --no-files

Disables file completion for command cmd.

complete --command cmd --force-files

Forces file completion for command cmd.

complete --command cmd --condition condition

Adds completions based on a specified condition.

complete --command cmd --description 'text'

Adds a description for the completion.

Useful Built-in Functions

__fish_seen_argument

Checks whether a specific argument has been used.

__fish_seen_subcommand_from

Checks if a specific subcommand has been used.

__fish_use_subcommand

Checks if any subcommand is used.

__fish_complete_directories

Completes directories.

__fish_complete_suffix

Completes files with a specific suffix.

__fish_complete_users

Lists all users for completion.
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