fish-shell/share/functions/trap.fish

# This defines a compatibility shim for the `trap` command found in other shells like bash and zsh.

function __trap_translate_signal
    set upper (echo $argv[1]|tr a-z A-Z)
    string replace -r '^SIG' '' -- $upper
end

function __trap_switch
    switch $argv[1]
        case EXIT exit
            echo --on-process-exit %self

        case '*'
            echo --on-signal $argv[1]
    end
end

function trap -d 'Perform an action when the shell receives a signal'

    set -l mode
    set -l cmd
    set -l sig

    set -l options
    set -l longopt
    set -l shortopt lph
    if not getopt -T >/dev/null
        # GNU getopt
        set longopt print,help,list-signals
        set options -o $shortopt -l $longopt --
        # Verify options
        if not getopt -n type $options $argv >/dev/null
            return 1
        end
    else
        # Old getopt, used on OS X
        set options $shortopt
        # Verify options
        if not getopt $options $argv >/dev/null
            return 1
        end
    end

    # Do the real getopt invocation
    set -l tmp (getopt $options $argv)

    # Break tmp up into an array
    set -l opt
    eval set opt $tmp

    while count $opt >/dev/null
        switch $opt[1]
            case -h --help
                __fish_print_help trap
                return 0

            case -p --print
                set mode print

            case -l --list-signals
                set mode list

            case --
                set -e opt[1]
                break

        end
        set -e opt[1]
    end

    if not count $mode >/dev/null

        switch (count $opt)

            case 0
                set mode print

            case 1
                set mode clear

            case '*'
                if test opt[1] = -
                    set -e opt[1]
                    set mode clear
                else
                    set mode set
                end
        end
    end

    switch $mode
        case clear
            for i in $opt
                set sig (__trap_translate_signal $i)
                if test $sig
                    functions -e __trap_handler_$sig
                end
            end

        case set
            set -l cmd $opt[1]
            set -e opt[1]

            for i in $opt
                set -l sig (__trap_translate_signal $i)
                set sw (__trap_switch $sig)

                if test $sig
                    echo "function __trap_handler_$sig $sw; $cmd; end" | source
                else
                    return 1
                end
            end

        case print
            set -l names

            if count $opt >/dev/null
                set names $opt
            else
                set names (functions -na| string match "__trap_handler_*" | string replace '__trap_handler_' '')
            end

            for i in $names

                set sig (__trap_translate_signal $i)

                if test sig
                    functions __trap_handler_$i
                else
                    return 1
                end

            end

        case list
            kill -l

    end

end