whatis

linux下bash的源码

#
# whatis -- and implementation of the 10th Edition Unix sh builtin `whatis'
#	    command.
#
# usage: whatis arg [...]
#
# For each argument, whatis prints the associated value as a parameter,
# builtin, function, alias, or executable file as appropriate.  In each
# case, the value is printed in a form which would yield the same value
# if typed as input to the shell itself.
#

whatis()
{
	local wusage='usage: whatis arg [arg...]'
	local fail=0

	if [ $# -eq 0 ] ; then
		echo "$wusage"
		return 1
	fi

	for arg
	do
		case $(builtin type -type $arg 2>/dev/null) in
		"alias")
			builtin alias "$arg"
			;;
		"function")
			builtin type "$arg" | sed 1d
			;;
		"builtin")
			echo builtin "$arg"
			;;
		"file")
			builtin type -path "$arg"
			;;
		*)
			# OK, we could have a variable, or we could have nada
			if [ "$(eval echo \${$arg+set})" = "set" ] ; then
				# It is a variable, and it is set
				echo -n "$arg="
				eval echo '\"'\$$arg'\"'
			else
				echo whatis: $arg: not found
				fail=1
			fi
			;;
		esac
	done
	return $fail
}