#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.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,
	O_ALL
};

int main(int argc, char **argv) {
	int opt;
	while ((opt = getopt(argc, argv, "ashrvm")) != -1) {
		switch (opt) {
			case 'a':
				for (int i = 0; i < O_ALL; i++)
					flags[i] = 1;
				break;

			case 's':
				flags[O_SYS] = 1;
				break;

			case 'n':
				flags[O_NODE] = 1;
				break;

			case 'r':
				flags[O_RELEASE] = 1;
				break;

			case 'v':
				flags[O_VERSION] = 1;
				break;

			case 'm':
				flags[O_MACHINE] = 1;
				break;

			default:
				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');
}