1  /* User and Group Database Example
       2     Copyright (C) 1991-2023 Free Software Foundation, Inc.
       3  
       4     This program is free software; you can redistribute it and/or
       5     modify it under the terms of the GNU General Public License
       6     as published by the Free Software Foundation; either version 2
       7     of the License, or (at your option) 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, see <https://www.gnu.org/licenses/>.
      16  */
      17  
      18  #include <grp.h>
      19  #include <pwd.h>
      20  #include <sys/types.h>
      21  #include <unistd.h>
      22  #include <stdlib.h>
      23  
      24  int
      25  main (void)
      26  {
      27    uid_t me;
      28    struct passwd *my_passwd;
      29    struct group *my_group;
      30    char **members;
      31  
      32    /* Get information about the user ID. */
      33    me = getuid ();
      34    my_passwd = getpwuid (me);
      35    if (!my_passwd)
      36      {
      37        printf ("Couldn't find out about user %d.\n", (int) me);
      38        exit (EXIT_FAILURE);
      39      }
      40  
      41    /* Print the information. */
      42    printf ("I am %s.\n", my_passwd->pw_gecos);
      43    printf ("My login name is %s.\n", my_passwd->pw_name);
      44    printf ("My uid is %d.\n", (int) (my_passwd->pw_uid));
      45    printf ("My home directory is %s.\n", my_passwd->pw_dir);
      46    printf ("My default shell is %s.\n", my_passwd->pw_shell);
      47  
      48    /* Get information about the default group ID. */
      49    my_group = getgrgid (my_passwd->pw_gid);
      50    if (!my_group)
      51      {
      52        printf ("Couldn't find out about group %d.\n",
      53  	      (int) my_passwd->pw_gid);
      54        exit (EXIT_FAILURE);
      55      }
      56  
      57    /* Print the information. */
      58    printf ("My default group is %s (%d).\n",
      59  	  my_group->gr_name, (int) (my_passwd->pw_gid));
      60    printf ("The members of this group are:\n");
      61    members = my_group->gr_mem;
      62    while (*members)
      63      {
      64        printf ("  %s\n", *(members));
      65        members++;
      66      }
      67  
      68    return EXIT_SUCCESS;
      69  }