posix/group_member.c

   1 /* `group_member' -- test if process is in a given group.
   2    Copyright (C) 1995, 1997, 2002 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <sys/types.h>
  21 #include <unistd.h>
  22 #include <stdlib.h>
  23 #include <limits.h>
  24
  25 #ifndef NGROUPS_MAX
  26 #define NGROUPS_MAX     16      /* First guess.  */
  27 #endif
  28
  29 int
  30 __group_member (gid)
  31      gid_t gid;
  32 {
  33   int n, size;
  34   gid_t *groups;
  35
  36   size = NGROUPS_MAX;
  37   do
  38     {
  39       groups = __alloca (size * sizeof *groups);
  40       n = __getgroups (size, groups);
  41       size *= 2;
  42     } while (n == size / 2);
  43
  44   while (n >= 0)
  45     if (groups[n--] == gid)
  46       return 1;
  47
  48   return 0;
  49 }
  50 weak_alias (__group_member, group_member)