src/logname.c

   1 /* logname -- print user's login name
   2    Copyright (C) 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 #include <config.h>
  19 #include <stdio.h>
  20 #include <sys/types.h>
  21 #include <getopt.h>
  22
  23 #include "version.h"
  24 #include "system.h"
  25
  26 /* The name this program was run with. */
  27 char *program_name;
  28
  29 /* If nonzero, display usage information and exit.  */
  30 static int show_help;
  31
  32 /* If nonzero, print the version on standard output and exit.  */
  33 static int show_version;
  34
  35 static struct option const long_options[] =
  36 {
  37   {"help", no_argument, &show_help, 1},
  38   {"version", no_argument, &show_version, 1},
  39   {0, 0, 0, 0}
  40 };
  41
  42 static void
  43 usage (int status)
  44 {
  45   if (status != 0)
  46     fprintf (stderr, _("Try `%s --help' for more information.\n"),
  47              program_name);
  48   else
  49     {
  50       printf (_("Usage: %s [OPTION]...\n"), program_name);
  51       printf (_("\
  52 Print the name of the current user.\n\
  53 \n\
  54   --help      display this help and exit\n\
  55   --version   output version information and exit\n\
  56 "));
  57     }
  58   exit (status);
  59 }
  60
  61 void
  62 main (int argc, char **argv)
  63 {
  64   register char *cp;
  65   int c;
  66
  67   program_name = argv[0];
  68
  69   while ((c = getopt_long (argc, argv, "", long_options, (int *) 0)) != EOF)
  70     {
  71       switch (c)
  72         {
  73         case 0:
  74           break;
  75
  76         default:
  77           usage (1);
  78         }
  79     }
  80
  81   if (show_version)
  82     {
  83       printf ("logname - %s\n", version_string);
  84       exit (0);
  85     }
  86
  87   if (show_help)
  88     usage (0);
  89
  90   if (argc - optind != 0)
  91     usage (1);
  92
  93   /* POSIX.2 requires using getlogin (or equivalent code).  */
  94   cp = getlogin ();
  95   if (cp)
  96     {
  97       puts (cp);
  98       exit (0);
  99     }
 100   /* POSIX.2 prohibits using a fallback technique.  */
 101   fprintf (stderr,_("%s: no login name\n"), argv[0]);
 102   exit (1);
 103 }