lib/getgroups.c

   1 /* provide consistent interface to getgroups for systems that don't allow N==0
   2    Copyright (C) 1996, 1999 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program; if not, write to the Free Software Foundation,
  16    Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.  */
  17
  18 /* written by Jim Meyering */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <sys/types.h>
  23
  24 char *xmalloc ();
  25
  26 /* On at least Ultrix 4.3 and NextStep 3.2, getgroups (0, 0) always fails.
  27    On other systems, it returns the number of supplemental groups for the
  28    process.  This function handles that special case and lets the system-
  29    provided function handle all others. */
  30
  31 int
  32 getgroups (size_t n, GETGROUPS_T *group)
  33 {
  34   int n_groups;
  35   GETGROUPS_T *gbuf;
  36
  37 #undef getgroups
  38
  39   if (n != 0)
  40     return getgroups (n, group);
  41
  42   n = 20;
  43   gbuf = NULL;
  44   while (1)
  45     {
  46       gbuf = (GETGROUPS_T *) xrealloc (gbuf, n * sizeof (GETGROUPS_T));
  47       n_groups = getgroups (n, gbuf);
  48       if (n_groups < n)
  49         break;
  50       n += 10;
  51     }
  52
  53   free (gbuf);
  54
  55   return n_groups;
  56 }