# fish_command_not_found - what to do when a command wasn’t found

## Synopsis

    function fish_command_not_found
       ...
    end

## Description

When fish tries to execute a command and can’t find it, it invokes this function.

It can print a message to tell you about it, and it often also checks for a missing package that would include the command.

Fish ships multiple handlers for various operating systems and chooses from them when this function is loaded, or you can define your own.

It receives the full commandline as one argument per token, so $argv[1] contains the missing command.

When you leave `fish_command_not_found` undefined (e.g. by adding an empty function file) or explicitly call `__fish_default_command_not_found_handler`, fish will just print a simple error.

## Example

A simple handler:

    function fish_command_not_found
        echo Did not find command $argv[1]
    end

    > flounder
    Did not find command flounder

Or the handler for OpenSUSE’s command-not-found:

    function fish_command_not_found
        /usr/bin/command-not-found $argv[1]
    end

Or the simple default handler:

    function fish_command_not_found
        __fish_default_command_not_found_handler $argv
    end

## Backwards compatibility

This command was introduced in fish 3.2.0. Previous versions of fish used the “fish_command_not_found” event instead.

To define a handler that works in older versions of fish as well, define it the old way:

    function __fish_command_not_found_handler --on-event fish_command_not_found
         echo COMMAND WAS NOT FOUND MY FRIEND $argv[1]
    end

in which case fish will define a `fish_command_not_found` that calls it, or define a wrapper:

    function fish_command_not_found
         echo "G'day mate, could not find your command: $argv"
    end

    function __fish_command_not_found_handler --on-event fish_command_not_found
         fish_command_not_found $argv
    end