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

const char
*get_operating_system()
{
#ifdef __gnu_linux__
	return "GNU/Linux";
#endif
#ifdef __FreeBSD__
	return "FreeBSD";
#endif
#ifdef __OpenBSD__
	return "OpenBSD";
#endif
#ifdef _WIN32
	return "Here's a USB stick kid, get a real operating system";
#endif
	return "Unknown operating system";
}

int
main(int argc, char *argv[])
{
	int c;
	int all = 0;
	int machine = 0;
	int node_name = 0;
	int kernel_release = 0;
	int kernel_name = 0;
	int operating_system = 0;
	int nothing = 0;
	struct utsname kernel_info;

	if(argc == 1)
		nothing = 1;
	while((c = getopt(argc, argv, "amnrsv")) != -1)
	{
		switch(c)
		{
		case 'a': all = 1; break;
		case 'm': machine = 1; break;
		case 'n': node_name = 1; break;
		case 'r': kernel_release = 1; break;
		case 's': kernel_name = 1; break;
		case 'v': operating_system = 1; break;
		}
	}

	uname(&kernel_info);

	if(all)
	{
		printf("%s %s %s %s %s %s\n",
			  kernel_info.sysname,
			  kernel_info.nodename,
			  kernel_info.release,
			  kernel_info.version,
			  kernel_info.machine,
			  get_operating_system());
	}
	else
	{
		if(machine)
			printf("%s ",kernel_info.machine);
		if(node_name)
			printf("%s ",kernel_info.nodename);
		if(kernel_release)
			printf("%s ",kernel_info.release);
		if(kernel_name || nothing)
			printf("%s ",kernel_info.sysname);
		if(operating_system)
			printf("%s",get_operating_system());
		printf("\n");

	}
	return 0;
}