getgroups.c

   1 /*
   2  * Print out the gids of all groups for the current user.  This is like
   3  * `id -G` on Linux, but it's too hard to find a portable equivalent.
   4  *
   5  * Copyright (C) 2002 Martin Pool
   6  * Copyright (C) 2003-2019 Wayne Davison
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License version 3 as
  10  * published by the Free Software Foundation.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License along
  18  * with this program; if not, visit the http://fsf.org website.
  19  */
  20
  21 #include "rsync.h"
  22
  23 int
  24 main(UNUSED(int argc), UNUSED(char *argv[]))
  25 {
  26         int n, i;
  27         gid_t *list;
  28         gid_t gid = MY_GID();
  29         int gid_in_list = 0;
  30
  31 #ifdef HAVE_GETGROUPS
  32         if ((n = getgroups(0, NULL)) < 0) {
  33                 perror("getgroups");
  34                 return 1;
  35         }
  36 #else
  37         n = 0;
  38 #endif
  39
  40         list = (gid_t*)malloc(sizeof (gid_t) * (n + 1));
  41         if (!list) {
  42                 fprintf(stderr, "out of memory!\n");
  43                 exit(1);
  44         }
  45
  46 #ifdef HAVE_GETGROUPS
  47         if (n > 0)
  48                 n = getgroups(n, list);
  49 #endif
  50
  51         for (i = 0; i < n; i++)  {
  52                 printf("%lu ", (unsigned long)list[i]);
  53                 if (list[i] == gid)
  54                         gid_in_list = 1;
  55         }
  56         /* The default gid might not be in the list on some systems. */
  57         if (!gid_in_list)
  58                 printf("%lu", (unsigned long)gid);
  59         printf("\n");
  60
  61         return 0;
  62 }