coreutils/src/hostid.c

/* print the hexadecimal identifier for the current host

   Copyright (C) 1997, 1999-2004, 2007-2011 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

/* Written by Jim Meyering.  */

#include <config.h>
#include <getopt.h>
#include <stdio.h>
#include <sys/types.h>

#include "system.h"
#include "long-options.h"
#include "error.h"
#include "quote.h"

/* The official name of this program (e.g., no `g' prefix).  */
#define PROGRAM_NAME "hostid"

#define AUTHORS proper_name ("Jim Meyering")

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    fprintf (stderr, _("Try `%s --help' for more information.\n"),
             program_name);
  else
    {
      printf (_("\
Usage: %s [OPTION]\n\
Print the numeric identifier (in hexadecimal) for the current host.\n\
\n\
"), program_name);
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
      emit_ancillary_info ();
    }
  exit (status);
}

int
main (int argc, char **argv)
{
  unsigned int id;

  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  parse_long_options (argc, argv, PROGRAM_NAME, PACKAGE_NAME, Version,
                      usage, AUTHORS, (char const *) NULL);
  if (getopt_long (argc, argv, "", NULL, NULL) != -1)
    usage (EXIT_FAILURE);

  if (optind < argc)
    {
      error (0, 0, _("extra operand %s"), quote (argv[optind]));
      usage (EXIT_FAILURE);
    }

  id = gethostid ();

  /* POSIX says gethostid returns a "32-bit identifier" but is silent
     whether it's sign-extended.  Turn off any sign-extension.  This
     is a no-op unless unsigned int is wider than 32 bits.  */
  id &= 0xffffffff;

  printf ("%08x\n", id);

  exit (EXIT_SUCCESS);
}