src/hostid.c

   1 /* print the hexadecimal identifier for the current host
   2
   3    Copyright (C) 1997-2023 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 "error.h"
  27 #include "quote.h"
  28
  29 /* The official name of this program (e.g., no 'g' prefix).  */
  30 #define PROGRAM_NAME "hostid"
  31
  32 #define AUTHORS proper_name ("Jim Meyering")
  33
  34 void
  35 usage (int status)
  36 {
  37   if (status != EXIT_SUCCESS)
  38     emit_try_help ();
  39   else
  40     {
  41       printf (_("\
  42 Usage: %s [OPTION]\n\
  43 Print the numeric identifier (in hexadecimal) for the current host.\n\
  44 \n\
  45 "), program_name);
  46       fputs (HELP_OPTION_DESCRIPTION, stdout);
  47       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  48       emit_ancillary_info (PROGRAM_NAME);
  49     }
  50   exit (status);
  51 }
  52
  53 int
  54 main (int argc, char **argv)
  55 {
  56   unsigned int id;
  57
  58   initialize_main (&argc, &argv);
  59   set_program_name (argv[0]);
  60   setlocale (LC_ALL, "");
  61   bindtextdomain (PACKAGE, LOCALEDIR);
  62   textdomain (PACKAGE);
  63
  64   atexit (close_stdout);
  65
  66   parse_gnu_standard_options_only (argc, argv, PROGRAM_NAME, PACKAGE_NAME,
  67                                    Version, true, usage, AUTHORS,
  68                                    (char const *) NULL);
  69
  70   if (optind < argc)
  71     {
  72       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  73       usage (EXIT_FAILURE);
  74     }
  75
  76   id = gethostid ();
  77
  78   /* POSIX says gethostid returns a "32-bit identifier" but is silent
  79      whether it's sign-extended.  Turn off any sign-extension.  This
  80      is a no-op unless unsigned int is wider than 32 bits.  */
  81   id &= 0xffffffff;
  82
  83   printf ("%08x\n", id);
  84
  85   return EXIT_SUCCESS;
  86 }