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<h3 class="section">29.15 User and Group Database Example</h3>

<p>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.

<pre class="smallexample">     #include &lt;grp.h&gt;
     #include &lt;pwd.h&gt;
     #include &lt;sys/types.h&gt;
     #include &lt;unistd.h&gt;
     #include &lt;stdlib.h&gt;
     
     int
     main (void)
     {
       uid_t me;
       struct passwd *my_passwd;
       struct group *my_group;
       char **members;
     
       /* <span class="roman">Get information about the user ID.</span> */
       me = getuid ();
       my_passwd = getpwuid (me);
       if (!my_passwd)
         {
           printf ("Couldn't find out about user %d.\n", (int) me);
           exit (EXIT_FAILURE);
         }
     
       /* <span class="roman">Print the information.</span> */
       printf ("I am %s.\n", my_passwd-&gt;pw_gecos);
       printf ("My login name is %s.\n", my_passwd-&gt;pw_name);
       printf ("My uid is %d.\n", (int) (my_passwd-&gt;pw_uid));
       printf ("My home directory is %s.\n", my_passwd-&gt;pw_dir);
       printf ("My default shell is %s.\n", my_passwd-&gt;pw_shell);
     
       /* <span class="roman">Get information about the default group ID.</span> */
       my_group = getgrgid (my_passwd-&gt;pw_gid);
       if (!my_group)
         {
           printf ("Couldn't find out about group %d.\n",
                   (int) my_passwd-&gt;pw_gid);
           exit (EXIT_FAILURE);
         }
     
       /* <span class="roman">Print the information.</span> */
       printf ("My default group is %s (%d).\n",
               my_group-&gt;gr_name, (int) (my_passwd-&gt;pw_gid));
       printf ("The members of this group are:\n");
       members = my_group-&gt;gr_mem;
       while (*members)
         {
           printf ("  %s\n", *(members));
           members++;
         }
     
       return EXIT_SUCCESS;
     }
</pre>
   <p>Here is some output from this program:

<pre class="smallexample">     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
</pre>
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