getgroupname
group = getgroupname(stb.st_gid, target, opts);
if (strcmp(group, getgroupname(statp->st_gid,
getgroupname(statp->st_gid,
char *getgroupname(gid_t, char *, opt_t);
if ((cp = getgroupname(stb.st_gid, target, o))
(cp = getgroupname(stb.st_gid,
getgroupname(stb.st_gid, target, options));