games/random/random.c

   1 /*      $NetBSD: random.c,v 1.13 2009/07/20 05:33:35 dholland Exp $     */
   2
   3 /*
   4  * Copyright (c) 1994
   5  *      The Regents of the University of California.  All rights reserved.
   6  *
   7  * This code is derived from software contributed to Berkeley by
   8  * Guy Harris at Network Appliance Corp.
   9  *
  10  * Redistribution and use in source and binary forms, with or without
  11  * modification, are permitted provided that the following conditions
  12  * are met:
  13  * 1. Redistributions of source code must retain the above copyright
  14  *    notice, this list of conditions and the following disclaimer.
  15  * 2. Redistributions in binary form must reproduce the above copyright
  16  *    notice, this list of conditions and the following disclaimer in the
  17  *    documentation and/or other materials provided with the distribution.
  18  * 3. Neither the name of the University nor the names of its contributors
  19  *    may be used to endorse or promote products derived from this software
  20  *    without specific prior written permission.
  21  *
  22  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  23  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  24  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  25  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  26  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  27  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  28  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  29  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  30  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  31  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  32  * SUCH DAMAGE.
  33  */
  34
  35 #include <sys/cdefs.h>
  36 #ifndef lint
  37 __COPYRIGHT("@(#) Copyright (c) 1994\
  38  The Regents of the University of California.  All rights reserved.");
  39 #endif /* not lint */
  40
  41 #ifndef lint
  42 #if 0
  43 static char sccsid[] = "@(#)random.c    8.6 (Berkeley) 6/1/94";
  44 #else
  45 __RCSID("$NetBSD: random.c,v 1.13 2009/07/20 05:33:35 dholland Exp $");
  46 #endif
  47 #endif /* not lint */
  48
  49 #include <sys/types.h>
  50 #include <sys/time.h>
  51
  52 #include <err.h>
  53 #include <errno.h>
  54 #include <stdio.h>
  55 #include <stdlib.h>
  56 #include <time.h>
  57 #include <unistd.h>
  58 #include <limits.h>
  59
  60 static void usage(void) __dead;
  61
  62 int
  63 main(int argc, char *argv[])
  64 {
  65         struct timeval tp;
  66         double denom;
  67         int ch, random_exit, selected, unbuffer_output;
  68         char *ep;
  69
  70         denom = 0;
  71         random_exit = unbuffer_output = 0;
  72         while ((ch = getopt(argc, argv, "er")) != -1)
  73                 switch (ch) {
  74                 case 'e':
  75                         random_exit = 1;
  76                         break;
  77                 case 'r':
  78                         unbuffer_output = 1;
  79                         break;
  80                 default:
  81                 case '?':
  82                         usage();
  83                         /* NOTREACHED */
  84                 }
  85
  86         argc -= optind;
  87         argv += optind;
  88
  89         switch (argc) {
  90         case 0:
  91                 denom = 2;
  92                 break;
  93         case 1:
  94                 errno = 0;
  95                 denom = strtod(*argv, &ep);
  96                 if (errno == ERANGE)
  97                         err(1, "%s", *argv);
  98                 if (denom == 0 || *ep != '\0')
  99                         errx(1, "denominator is not valid.");
 100                 break;
 101         default:
 102                 usage();
 103                 /* NOTREACHED */
 104         }
 105
 106         (void)gettimeofday(&tp, NULL);
 107         srandom((unsigned long)tp.tv_usec + tp.tv_sec + getpid());
 108
 109         /* Compute a random exit status between 0 and denom - 1. */
 110         if (random_exit)
 111                 return ((denom * random()) / RANDOM_MAX);
 112
 113         /*
 114          * Act as a filter, randomly choosing lines of the standard input
 115          * to write to the standard output.
 116          */
 117         if (unbuffer_output)
 118                 setbuf(stdout, NULL);
 119
 120         /*
 121          * Select whether to print the first line.  (Prime the pump.)
 122          * We find a random number between 0 and denom - 1 and, if it's
 123          * 0 (which has a 1 / denom chance of being true), we select the
 124          * line.
 125          */
 126         selected = (int)(denom * random() / RANDOM_MAX) == 0;
 127         while ((ch = getchar()) != EOF) {
 128                 if (selected)
 129                         (void)putchar(ch);
 130                 if (ch == '\n') {
 131                         /* End of that line.  See if we got an error. */
 132                         if (ferror(stdout))
 133                                 err(2, "stdout");
 134
 135                         /* Now see if the next line is to be printed. */
 136                         selected = (int)(denom * random() / RANDOM_MAX) == 0;
 137                 }
 138         }
 139         if (ferror(stdin))
 140                 err(2, "stdin");
 141         exit (0);
 142
 143         return 0;
 144 }
 145
 146 static void
 147 usage(void)
 148 {
 149
 150         (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
 151         exit(1);
 152 }