src/hostid.c

   1 /* print the hexadecimal identifier for the current host
   2
   3    Copyright (C) 1997-2015 Free Software Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation, either version 3 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #include <config.h>
  21 #include <getopt.h>
  22 #include <stdio.h>
  23 #include <sys/types.h>
  24
  25 #include "system.h"
  26 #include "long-options.h"
  27 #include "error.h"
  28 #include "quote.h"
  29
  30 /* The official name of this program (e.g., no 'g' prefix).  */
  31 #define PROGRAM_NAME "hostid"
  32
  33 #define AUTHORS proper_name ("Jim Meyering")
  34
  35 void
  36 usage (int status)
  37 {
  38   if (status != EXIT_SUCCESS)
  39     emit_try_help ();
  40   else
  41     {
  42       printf (_("\
  43 Usage: %s [OPTION]\n\
  44 Print the numeric identifier (in hexadecimal) for the current host.\n\
  45 \n\
  46 "), program_name);
  47       fputs (HELP_OPTION_DESCRIPTION, stdout);
  48       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  49       emit_ancillary_info (PROGRAM_NAME);
  50     }
  51   exit (status);
  52 }
  53
  54 int
  55 main (int argc, char **argv)
  56 {
  57   unsigned int id;
  58
  59   initialize_main (&argc, &argv);
  60   set_program_name (argv[0]);
  61   setlocale (LC_ALL, "");
  62   bindtextdomain (PACKAGE, LOCALEDIR);
  63   textdomain (PACKAGE);
  64
  65   atexit (close_stdout);
  66
  67   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
  68                       usage, AUTHORS, (char const *) NULL);
  69   if (getopt_long (argc, argv, "", NULL, NULL) != -1)
  70     usage (EXIT_FAILURE);
  71
  72   if (optind < argc)
  73     {
  74       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  75       usage (EXIT_FAILURE);
  76     }
  77
  78   id = gethostid ();
  79
  80   /* POSIX says gethostid returns a "32-bit identifier" but is silent
  81      whether it's sign-extended.  Turn off any sign-extension.  This
  82      is a no-op unless unsigned int is wider than 32 bits.  */
  83   id &= 0xffffffff;
  84
  85   printf ("%08x\n", id);
  86
  87   return EXIT_SUCCESS;
  88 }