ref: d05dbeb9a44c298a01e741c1bffb68591b87b5f5
dir: /sys/src/ape/lib/ap/plan9/getgrgid.c/
#include <stddef.h>
#include <grp.h>
extern int _getpw(int *, char **, char **);
extern char **_grpmems(char *);
static struct group holdgroup;
struct group *
getgrgid(gid_t gid)
{
	int num;
	char *nam, *mem;
	num = gid;
	nam = 0;
	mem = 0;
	if(_getpw(&num, &nam, &mem)){
		holdgroup.gr_name = nam;
		holdgroup.gr_passwd = "";
		holdgroup.gr_gid = num;
		holdgroup.gr_mem = _grpmems(mem);
		return &holdgroup;
	}
	return NULL;
}