random/random.c

   1 /*      $NetBSD: random.c,v 1.15 2020/07/26 15:24:00 nia 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 1.15 2020/07/26 15:24:00 nia 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         double denom;
  66         int ch, random_exit, selected, unbuffer_output;
  67         char *ep;
  68
  69         denom = 0;
  70         random_exit = unbuffer_output = 0;
  71         while ((ch = getopt(argc, argv, "er")) != -1)
  72                 switch (ch) {
  73                 case 'e':
  74                         random_exit = 1;
  75                         break;
  76                 case 'r':
  77                         unbuffer_output = 1;
  78                         break;
  79                 default:
  80                 case '?':
  81                         usage();
  82                         /* NOTREACHED */
  83                 }
  84
  85         argc -= optind;
  86         argv += optind;
  87
  88         switch (argc) {
  89         case 0:
  90                 denom = 2;
  91                 break;
  92         case 1:
  93                 errno = 0;
  94                 denom = strtod(*argv, &ep);
  95                 if (errno == ERANGE)
  96                         err(1, "%s", *argv);
  97                 if (denom == 0 || *ep != '\0')
  98                         errx(1, "denominator is not valid.");
  99                 break;
 100         default:
 101                 usage();
 102                 /* NOTREACHED */
 103         }
 104
 105         /* Compute a random exit status between 0 and denom - 1. */
 106         if (random_exit)
 107                 return arc4random_uniform(denom);
 108
 109         /*
 110          * Act as a filter, randomly choosing lines of the standard input
 111          * to write to the standard output.
 112          */
 113         if (unbuffer_output)
 114                 setbuf(stdout, NULL);
 115
 116         /*
 117          * Select whether to print the first line.  (Prime the pump.)
 118          * We find a random number between 0 and denom - 1 and, if it's
 119          * 0 (which has a 1 / denom chance of being true), we select the
 120          * line.
 121          */
 122         selected = (arc4random_uniform(denom) == 0);
 123         while ((ch = getchar()) != EOF) {
 124                 if (selected)
 125                         (void)putchar(ch);
 126                 if (ch == '\n') {
 127                         /* End of that line.  See if we got an error. */
 128                         if (ferror(stdout))
 129                                 err(2, "stdout");
 130
 131                         /* Now see if the next line is to be printed. */
 132                         selected = (arc4random_uniform(denom) == 0);
 133                 }
 134         }
 135         if (ferror(stdin))
 136                 err(2, "stdin");
 137         exit (0);
 138
 139         return 0;
 140 }
 141
 142 static void
 143 usage(void)
 144 {
 145
 146         (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
 147         exit(1);
 148 }