src/hostid.c

   1 /* print the hexadecimal identifier for the current host
   2
   3    Copyright (C) 1997-2024 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 <https://www.gnu.org/licenses/>.  */
  17
  18 /* Written by Jim Meyering.  */
  19
  20 #include <config.h>
  21 #include <stdio.h>
  22 #include <sys/types.h>
  23
  24 #include "system.h"
  25 #include "long-options.h"
  26 #include "quote.h"
  27
  28 /* The official name of this program (e.g., no 'g' prefix).  */
  29 #define PROGRAM_NAME "hostid"
  30
  31 #define AUTHORS proper_name ("Jim Meyering")
  32
  33 void
  34 usage (int status)
  35 {
  36   if (status != EXIT_SUCCESS)
  37     emit_try_help ();
  38   else
  39     {
  40       printf (_("\
  41 Usage: %s [OPTION]\n\
  42 Print the numeric identifier (in hexadecimal) for the current host.\n\
  43 \n\
  44 "), program_name);
  45       fputs (HELP_OPTION_DESCRIPTION, stdout);
  46       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  47       emit_ancillary_info (PROGRAM_NAME);
  48     }
  49   exit (status);
  50 }
  51
  52 int
  53 main (int argc, char **argv)
  54 {
  55   unsigned int id;
  56
  57   initialize_main (&argc, &argv);
  58   set_program_name (argv[0]);
  59   setlocale (LC_ALL, "");
  60   bindtextdomain (PACKAGE, LOCALEDIR);
  61   textdomain (PACKAGE);
  62
  63   atexit (close_stdout);
  64
  65   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  66                                    Version, true, usage, AUTHORS,
  67                                    (char const *) nullptr);
  68
  69   if (optind < argc)
  70     {
  71       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  72       usage (EXIT_FAILURE);
  73     }
  74
  75   id = gethostid ();
  76
  77   /* POSIX says gethostid returns a "32-bit identifier" but is silent
  78      whether it's sign-extended.  Turn off any sign-extension.  This
  79      is a no-op unless unsigned int is wider than 32 bits.  */
  80   id &= 0xffffffff;
  81
  82   printf ("%08x\n", id);
  83
  84   return EXIT_SUCCESS;
  85 }