#include <sys/utsname.h>

#include <stdio.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
	int c;
	int kernel_name = 0, nodename = 0, kernel_release = 0,
	    kernel_version = 0, machine = 0;
	struct utsname sysname;

	if (uname(&sysname) == -1) {
		printf("An unknown error occured.\n");
	}

	while (--argc > 0)
		if ((*++argv)[0] == '-')
			while (c = *++argv[0])
				switch (c) {
				case 'a':
					kernel_name = 1;
					nodename = 1;
					kernel_release = 1;
					kernel_version = 1;
					machine = 1;
					break;
				case 's':
					kernel_name = 1;
					break;
				case 'n':
					nodename = 1;
					break;
				case 'r':
					kernel_release = 1;
					break;
				case 'v':
					kernel_version = 1;
					break;
				case 'm':
					machine = 1;
					break;
				default:
					printf("Unknown option.\n");
					printf("Usage: uname -asnrvm\n");
					exit(0);
				}

	if (!kernel_name && !nodename && !kernel_release && !kernel_version &&
			!machine) {
		printf("Usage: uname -asnrvm\n");
		exit(0);
	}

	if (kernel_name)
		printf("%s ", sysname.sysname);

	if (nodename)
		printf("%s ", sysname.nodename);

	if (kernel_release)
		printf("%s ", sysname.release);

	if (kernel_version)
		printf("%s ", sysname.version);

	if (machine)
		printf("%s ", sysname.machine);

	putchar('\n');

	return 0;
}