optional_argument   18 tools/power/cpupower/utils/cpupower-info.c      {"perf-bias", optional_argument, NULL, 'b'},
optional_argument  595 tools/usb/usbip/src/usbipd.c 		{ "pid",      optional_argument, NULL, 'P' },
optional_argument 1356 tools/vm/slabinfo.c 	{ "debug", optional_argument, NULL, 'd' },