fish-shell/share/functions/trap.fish

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
			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 $sig
					eval "function __trap_handler_$sig $sw; $cmd; end"
				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