src/hostid.c

   1 /* print the hexadecimal identifier for the current host
   2
   3    Copyright (C) 1997-2019 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 <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 static struct option const long_options[] =
  36 {
  37   {NULL, 0, NULL, 0}
  38 };
  39
  40 void
  41 usage (int status)
  42 {
  43   if (status != EXIT_SUCCESS)
  44     emit_try_help ();
  45   else
  46     {
  47       printf (_("\
  48 Usage: %s [OPTION]\n\
  49 Print the numeric identifier (in hexadecimal) for the current host.\n\
  50 \n\
  51 "), program_name);
  52       fputs (HELP_OPTION_DESCRIPTION, stdout);
  53       fputs (VERSION_OPTION_DESCRIPTION, stdout);
  54       emit_ancillary_info (PROGRAM_NAME);
  55     }
  56   exit (status);
  57 }
  58
  59 int
  60 main (int argc, char **argv)
  61 {
  62   unsigned int id;
  63
  64   initialize_main (&argc, &argv);
  65   set_program_name (argv[0]);
  66   setlocale (LC_ALL, "");
  67   bindtextdomain (PACKAGE, LOCALEDIR);
  68   textdomain (PACKAGE);
  69
  70   atexit (close_stdout);
  71
  72   parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
  73                       usage, AUTHORS, (char const *) NULL);
  74   if (getopt_long (argc, argv, "", long_options, NULL) != -1)
  75     usage (EXIT_FAILURE);
  76
  77   if (optind < argc)
  78     {
  79       error (0, 0, _("extra operand %s"), quote (argv[optind]));
  80       usage (EXIT_FAILURE);
  81     }
  82
  83   id = gethostid ();
  84
  85   /* POSIX says gethostid returns a "32-bit identifier" but is silent
  86      whether it's sign-extended.  Turn off any sign-extension.  This
  87      is a no-op unless unsigned int is wider than 32 bits.  */
  88   id &= 0xffffffff;
  89
  90   printf ("%08x\n", id);
  91
  92   return EXIT_SUCCESS;
  93 }