idmap_getwinnamebygid
rc = idmap_getwinnamebygid(gid, 0, &idmap_buf, NULL);
(void) idmap_getwinnamebygid(rid, flag,
extern idmap_stat idmap_getwinnamebygid(gid_t, int, char **, char **);
error = idmap_getwinnamebygid(who,
stat = idmap_getwinnamebygid(pid, flag, &name, NULL);