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) 2003-2020 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 main(UNUSED(int argc), UNUSED(char *argv[]))
  24 {
  25         int n, i;
  26         gid_t *list;
  27         gid_t gid = MY_GID();
  28         int gid_in_list = 0;
  29
  30 #ifdef HAVE_GETGROUPS
  31         if ((n = getgroups(0, NULL)) < 0) {
  32                 perror("getgroups");
  33                 return 1;
  34         }
  35 #else
  36         n = 0;
  37 #endif
  38
  39         list = (gid_t*)malloc(sizeof (gid_t) * (n + 1));
  40         if (!list) {
  41                 fprintf(stderr, "out of memory!\n");
  42                 exit(1);
  43         }
  44
  45 #ifdef HAVE_GETGROUPS
  46         if (n > 0)
  47                 n = getgroups(n, list);
  48 #endif
  49
  50         for (i = 0; i < n; i++)  {
  51                 printf("%lu ", (unsigned long)list[i]);
  52                 if (list[i] == gid)
  53                         gid_in_list = 1;
  54         }
  55         /* The default gid might not be in the list on some systems. */
  56         if (!gid_in_list)
  57                 printf("%lu", (unsigned long)gid);
  58         printf("\n");
  59
  60         return 0;
  61 }