#define _BSD_SOURCE
#include <errno.h>
#include <pwd.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>

int main(int argc, char **argv) {
	if(argc < 3) {
		fprintf(stderr, "Usage: %s username command [arguments]\n", argv[0]);
		return 1;
	}

	const char *username = argv[1];
	errno = 0;
	struct passwd *passwd_entry = getpwnam(username);
	if(passwd_entry == NULL) {
		perror("getpwnam");
		return 1;
	}

	uid_t ruid = passwd_entry->pw_uid;

	if(setreuid(ruid, -1) != 0) {
		perror("getpwnam");
		return 1;
	}

	char **daemon_argv = &argv[2];
	const char *daemon_command = daemon_argv[0];

	execvp(daemon_command, daemon_argv);

	perror("execvp");
	return 1;
}