#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <sys/utsname.h>

/* sys node release version machine */
int flags[] = {0, 0, 0, 0, 0};
enum {
	O_SYS,
	O_NODE,
	O_RELEASE,
	O_VERSION,
	O_MACHINE
};

int main(const int argc, const char **argv) {
	for (int i = 0; i < argc; i++) {
		if (!strcmp("-a", argv[i])) {
			for (size_t i = 0; i < sizeof(flags) / sizeof(flags[0]); i++)
				flags[i] = 1;
		}

		else if (!strcmp("-s", argv[i]))
			flags[O_SYS] = 1;

		else if (!strcmp("-n", argv[i]))
			flags[O_NODE] = 1;

		else if (!strcmp("-r", argv[i]))
			flags[O_RELEASE] = 1;

		else if (!strcmp("-v", argv[i]))
			flags[O_VERSION] = 1;

		else if (!strcmp("-m", argv[i]))
			flags[O_MACHINE] = 1;

		else if (!strcmp("-h", argv[i])) {
			printf("uname [-a (All)] [-s (Sys)] [-n (Nodename)] [-r (Release)] [-v (Version)] [-m (Machine)]\n");
			return 0;
		}
	}

	struct utsname uts;
	if (uname(&uts)) {
		fprintf(stderr, "uname: %s", strerror(errno));
		return 1;
	}

	if (flags[O_SYS] || argc == 1)
		printf("%s ", uts.sysname);

	if (flags[O_NODE])
		printf("%s ", uts.nodename);

	if (flags[O_RELEASE])
		printf("%s ", uts.release);

	if (flags[O_VERSION])
		printf("%s ", uts.version);

	if (flags[O_MACHINE])
		printf("%s ", uts.machine);

	putchar('\n');
}