Fish Shell:
Organizing code into functions

How to:

In Fish, you write a function with function keyword, give it a name, and end with end. Here’s a simple one:

function hello
    echo "Hello, World!"
end

hello

Output:

Hello, World!

Now, let’s make it greet a user:

function greet
    set user (whoami)
    echo "Hey there, $user!"
end

greet

Output:

Hey there, your_username!

To save it across sessions, use funcsave greet.

Deep Dive

Fish Shell functions are like mini-scripts — you can shove pretty much anything in there. Historically, the concept of functions in shell scripting has saved countless hours of repetitive typing and debugging. Unlike programming languages like Python, Shell functions are more about convenience than structure.

Some shells, like Bash, use function or just straight braces. Fish sticks to function ... end— clear and readable. Inside Fish functions, you get all the bells and whistles: parameters, local variables with set -l, and you can even define a function inside another function.

You won’t need a return value because Fish isn’t big on that; your function’s output is its return. And if you want persistent functions available for future sessions, remember funcsave.

See Also

• The fish tutorial on functions: https://fishshell.com/docs/current/tutorial.html#tut_functions

Function commands

• function — Create a function
• functions — Print or erase functions
• funcsave — Save the definition of a function to the user’s autoload directory
• funced — Edit a function interactively