(libc.info.gz) Database Example

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 29.15 User and Group Database Example
 =====================================
 
 Here is an example program showing the use of the system database
 inquiry functions.  The program prints some information about the user
 running the program.
 
      #include <grp.h>
      #include <pwd.h>
      #include <sys/types.h>
      #include <unistd.h>
      #include <stdlib.h>
 
      int
      main (void)
      {
        uid_t me;
        struct passwd *my_passwd;
        struct group *my_group;
        char **members;
 
        /* Get information about the user ID. */
        me = getuid ();
        my_passwd = getpwuid (me);
        if (!my_passwd)
          {
            printf ("Couldn't find out about user %d.\n", (int) me);
            exit (EXIT_FAILURE);
          }
 
        /* Print the information. */
        printf ("I am %s.\n", my_passwd->pw_gecos);
        printf ("My login name is %s.\n", my_passwd->pw_name);
        printf ("My uid is %d.\n", (int) (my_passwd->pw_uid));
        printf ("My home directory is %s.\n", my_passwd->pw_dir);
        printf ("My default shell is %s.\n", my_passwd->pw_shell);
 
        /* Get information about the default group ID. */
        my_group = getgrgid (my_passwd->pw_gid);
        if (!my_group)
          {
            printf ("Couldn't find out about group %d.\n",
                    (int) my_passwd->pw_gid);
            exit (EXIT_FAILURE);
          }
 
        /* Print the information. */
        printf ("My default group is %s (%d).\n",
                my_group->gr_name, (int) (my_passwd->pw_gid));
        printf ("The members of this group are:\n");
        members = my_group->gr_mem;
        while (*members)
          {
            printf ("  %s\n", *(members));
            members++;
          }
 
        return EXIT_SUCCESS;
      }
 
    Here is some output from this program:
 
      I am Throckmorton Snurd.
      My login name is snurd.
      My uid is 31093.
      My home directory is /home/fsg/snurd.
      My default shell is /bin/sh.
      My default group is guest (12).
      The members of this group are:
        friedman
        tami
 

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