src/whoami.c

   1 /* whoami -- print effective userid
   2    Copyright (C) 89, 90, 91, 92, 93, 94, 1995 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 2, or (at your option)
   7    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, write to the Free Software
  16    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  17
  18 /* Equivalent to `id -un'. */
  19 /* Written by Richard Mlynarik. */
  20
  21 #include <config.h>
  22 #include <stdio.h>
  23 #include <sys/types.h>
  24 #include <pwd.h>
  25 #include <getopt.h>
  26
  27 #include "version.h"
  28 #include "system.h"
  29
  30 /* The name this program was run with. */
  31 char *program_name;
  32
  33 /* If nonzero, display usage information and exit.  */
  34 static int show_help;
  35
  36 /* If nonzero, print the version on standard output and exit.  */
  37 static int show_version;
  38
  39 static struct option const long_options[] =
  40 {
  41   {"help", no_argument, &show_help, 1},
  42   {"version", no_argument, &show_version, 1},
  43   {0, 0, 0, 0}
  44 };
  45
  46 static void
  47 usage (int status)
  48 {
  49   if (status != 0)
  50     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  51              program_name);
  52   else
  53     {
  54       printf (_("Usage: %s [OPTION]...\n"), program_name);
  55       printf (_("\
  56 Print the user name associated with the current effective user id.\n\
  57 Same as id -un.\n\
  58 \n\
  59   --help      display this help and exit\n\
  60   --version   output version information and exit\n"));
  61     }
  62   exit (status);
  63 }
  64
  65 void
  66 main (int argc, char **argv)
  67 {
  68   register struct passwd *pw;
  69   register uid_t uid;
  70   int c;
  71
  72   program_name = argv[0];
  73
  74   while ((c = getopt_long (argc, argv, "", long_options, (int *) 0)) != EOF)
  75     {
  76       switch (c)
  77         {
  78         case 0:
  79           break;
  80
  81         default:
  82           usage (1);
  83         }
  84     }
  85
  86   if (show_version)
  87     {
  88       printf ("whoami - %s\n", version_string);
  89       exit (0);
  90     }
  91
  92   if (show_help)
  93     usage (0);
  94
  95
  96   if (optind != argc)
  97     usage (1);
  98
  99   uid = geteuid ();
 100   pw = getpwuid (uid);
 101   if (pw)
 102     {
 103       puts (pw->pw_name);
 104       exit (0);
 105     }
 106   fprintf (stderr, _("%s: cannot find username for UID %u\n"),
 107            program_name, (unsigned) uid);
 108   exit (1);
 109 }