int read_supplementary_groups(char *user)
{
    int ngroups = 16;
    gid_t groups = (gid_t *)malloc(ngroups*sizeof(gid_t))
    struct passwd pw = getpwnam(user);
    if(getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) < 0){
        groups = (gid_t *)realloc(nrougps*sizeof(gid_t));
        getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups);
    }
    return groups;
}

int main(int argc, char **argv)
{
    read_supplementary_groups(getenv("USER"));
    return 0;
}