/* readutmp - Basic test of existing utmp/utmpx access.
  Copyright (C) 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018,
  2019, 2020, 2021 Free Software Foundation, Inc.

  This file is part of GNU Inetutils.

  GNU Inetutils 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.

  GNU Inetutils 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 Mats Erik Andersson.  */

/* Readutmp reads the system's standard UTMP or UTMPX file
 * and verifies that a spcific user is logged in.
 *
 * Invocation:
 *
 *    readutmp
 *    readutmp name
 *
 * The first mode investigates the present user.
 */

#include <config.h>

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <pwd.h>

#include <progname.h>
#include <readutmp.h>
#include <xalloc.h>

int
main (int argc, char *argv[])
{
#ifndef HAVE_GETUTXUSER
  STRUCT_UTMP *utmpp, *uptr;
  size_t count;
#endif
  struct passwd *pw;
  char *name;
  int found = 0;

  set_program_name (argv[0]);

  if (argc > 1)
    pw = getpwnam (argv[1]);
  else
    pw = getpwuid (getuid ());

  if (pw)
    name = xstrdup (pw->pw_name);
  else
    {
      fprintf (stderr, "Unknown user '%s'.\n",
	       (argc > 1) ? argv[1] : "my own UID");
      return EXIT_FAILURE;
    }

#ifdef HAVE_GETUTXUSER
  setutxent ();
  found = (getutxuser (name) != 0);
  endutxent ();
#else /* !HAVE_GETUTXUSER */
  if (read_utmp (UTMP_FILE, &count, &utmpp, READ_UTMP_USER_PROCESS))
    {
      perror ("read_utmp");
      return EXIT_FAILURE;
    }

  for (uptr = utmpp; uptr < utmpp + count; uptr++)
    if (!strncmp (name, UT_USER (uptr), sizeof (UT_USER (uptr))))
      {
	found = 1;
	break;
      }

  free (utmpp);
#endif /* HAVE_GETUTXUSER */

  if (found)
    return EXIT_SUCCESS;

  fprintf (stderr, "User '%s' is not logged in.\n", name);
  return EXIT_FAILURE;
}
