/*
utxsplit -- makes smaller wtmpx-format files from larger ones
Copyright (C) 1999 Ed Cashin

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 2
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, write to the Free Software
Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.

*/
#include	<stdio.h>
#include	<stdlib.h>
#include	<string.h>
#include	<fcntl.h>
#include	<unistd.h>
#include	<utmpx.h>


int main(int argc, char *argv[])
{
    extern char		 *optarg;
    extern int		 optind;
    int			 c, i;
    int			 begin	 = 0; /* beginning utmpx entry
                                         (zero-based offsets) */
    int			 end	 = 0; /* the zero-based offset of the
                                         ending entry (zero means do
                                         all) */
    char		 *infile = NULL;
    char		 *outfile = NULL;

    struct utmpx	 utx;
    int			 in_fd, out_fd;

    char		 *usage
      = "usage: utxsplit [ -b begin ] [ -e end ] -f {filename} > outfile\n"
      "... where begin is number of first utmpx record to read\n"
      "    and end is number of last one (0 means do them all)\n"
      "    filename is the utmpx-format file to read entries from\n"
      "    outfile is the new utmpx-format file\n";


    while ((c = getopt(argc, argv, "b:e:o:i:")) != EOF) {
      switch (c) {
	case 'b':
	  begin		 = atoi(optarg);
	  break;
	case 'e':
	  end		 = atoi(optarg);
	  break;
	case 'i':
	  infile	 = strdup(optarg);
	  break;
	case 'o':
	  outfile	 = strdup(optarg);
	  break;
	case '?':
	  fprintf(stderr, usage);
	  exit (2);
	  break;
	default:
	  break;
      }	/* end switch */
    } /* end while */

    /* (now optind is the index of any remaining cmd-line args) */

    /* don't need to do this because for loop fails on weird values of
       begin */
//     if (begin < 0)		/* handle weird begin-end numbers */
// 	 begin	 = 0;

    /* don't need to do this: weird end will default to reading to EOF */
//     if (end > 0 && end < begin)
// 	 end	 = begin;

    if ( (! infile) || (! outfile) ) {
      fprintf(stderr, usage);
      exit(EXIT_FAILURE);
    }
    if ( (in_fd = open(infile, O_RDONLY)) == -1 ) {
      perror(infile);
      exit(EXIT_FAILURE);
    }
    if ( (out_fd = open(outfile, O_WRONLY | O_CREAT | O_TRUNC, 0664)) == -1 ) {
      perror(outfile);
      exit(EXIT_FAILURE);
    }
    
/*      while (read(in_fd, &utx, sizeof(utx)) == sizeof(utx)) */
/*        printf("user=%s:type=%d\n", utx.ut_user, utx.ut_type); */

    for (i = 1; i < begin; ++i) {
      if (read(in_fd, &utx, sizeof(utx)) != sizeof(utx)) {
	fprintf(stderr, "no more entries\n");
	exit(EXIT_SUCCESS);
      }
    }
    ++end;			/* end now points to the number of one
                                   _after_ the last one they want */
    while ( i++ != end ) {
      if (read(in_fd, &utx, sizeof(utx)) != sizeof(utx)) {
	fprintf(stderr, "no more entries\n");
	exit(EXIT_SUCCESS);
      }
      if (write(out_fd, &utx, sizeof(utx)) == -1) {
  	perror("writing to output"); 
 	exit(EXIT_FAILURE); 
      }
    }
    
    if (infile)
      free(infile);
    if (outfile)
      free(outfile);

    return 0;
}