1#define _GNU_SOURCE
 2#include <grp.h>
 3#include <limits.h>
 4
 5int initgroups(const char *user, gid_t gid)
 6{
 7	gid_t groups[NGROUPS_MAX];
 8	int count = NGROUPS_MAX;
 9	if (getgrouplist(user, gid, groups, &count) < 0) return -1;
10	return setgroups(count, groups);
11}