#include <limits.h> /* LOGIN_NAME_MAX */
#include <stdbool.h>
#include <stdio.h> /* fprintf(3) */
#include <stdlib.h> /* stderr, stdout */
#include <sysexits.h>
#include <unistd.h> /* getuid(2), geteuid(2), getopt(3) */
#include "usefulmacros.h"

int main(int argc, char *argv[]){
	int c;
	char mode;
	bool n;
	char name[LOGIN_NAME_MAX];
	bool r;
	uid_t euid;
	uid_t uid;

	NOARGVZERO(argv);

	mode = 0;
	n = false;
	r = false;

	while((c = getopt(argc, argv, "Gghnru")) != -1)
		switch(c){
		case 'G': case 'g': case 'u':
			if(mode == 0){
				mode = c;
				break;
			}
			/* FALLTHROUGH */
		case 'h': default: usage:
			fprintf(stderr, "Usage: %s [-G]|[-g]|[-u] (-rn) (user)\n", argv[0]);
			return EX_USAGE;
		case 'n':
			n = true;
			break;
		case 'r':
			r = true;
			break;
		}
	
	switch(mode){
		case 0:
			goto usage;
		case 'G':
		case 'g':
			return EX_SOFTWARE;
		case 'u':
			euid = geteuid();
			uid = getuid();
			if(!n){
				if(r || euid != uid)
					fprintf(stdout, "%u\n", uid);
				if(!r)
					fprintf(stdout, "%u\n", euid);
			}else
				{}
				/* Both busybox and GNU coreutils (according to straces) parse passwd(5)
				 * for this. TODO. */
			break;
		default:
			return EX_SOFTWARE;
	}
	return EX_OK;
}