substr

linux下bash的源码

#
# substr -- a function to emulate the ancient ksh builtin
#

#
# -l == shortest from left
# -L == longest from left
# -r == shortest from right (the default)
# -R == longest from right

substr()
{
	local flag pat str
	local usage="usage: substr -lLrR pat string or substr string pat"

	case "$1" in
	-l | -L | -r | -R)
		flag="$1"
		pat="$2"
		shift 2
		;;
	-*)
		echo "substr: unknown option: $1"
		echo "$usage"
		return 1
		;;
	*)
		flag="-r"
		pat="$2"
		;;
	esac

	if [ "$#" -eq 0 -o "$#" -gt 2 ] ; then
		echo "substr: bad argument count"
		return 2
	fi

	str="$1"

	#
	# We don't want -f, but we don't want to turn it back on if
	# we didn't have it already
	#
	case "$-" in
	"*f*")
		;;
	*)
		fng=1
		set -f
		;;
	esac

	case "$flag" in
	-l)
		str="${str#$pat}"		# substr -l pat string
		;;
	-L)
		str="${str##$pat}"		# substr -L pat string
		;;
	-r)
		str="${str%$pat}"		# substr -r pat string
		;;
	-R)
		str="${str%%$pat}"		# substr -R pat string
		;;
	*)
		str="${str%$2}"			# substr string pat
		;;
	esac

	echo "$str"

	#
	# If we had file name generation when we started, re-enable it
	#
	if [ "$fng" = "1" ] ; then
		set +f
	fi
}