random/random.c

   1 /*      $NetBSD: random.c,v 1.8 2003/08/07 09:37:35 agc 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\n\
  38         The Regents of the University of California.  All rights reserved.\n");
  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 1.8 2003/08/07 09:37:35 agc 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 #define MAXRANDOM       2147483647
  61
  62 int  main __P((int, char **));
  63 void usage __P((void)) __attribute__((__noreturn__));
  64
  65 int
  66 main(argc, argv)
  67         int argc;
  68         char *argv[];
  69 {
  70         struct timeval tp;
  71         double denom;
  72         int ch, random_exit, selected, unbuffer_output;
  73         char *ep;
  74
  75         denom = 0;
  76         random_exit = unbuffer_output = 0;
  77         while ((ch = getopt(argc, argv, "er")) != -1)
  78                 switch (ch) {
  79                 case 'e':
  80                         random_exit = 1;
  81                         break;
  82                 case 'r':
  83                         unbuffer_output = 1;
  84                         break;
  85                 default:
  86                 case '?':
  87                         usage();
  88                         /* NOTREACHED */
  89                 }
  90
  91         argc -= optind;
  92         argv += optind;
  93
  94         switch (argc) {
  95         case 0:
  96                 denom = 2;
  97                 break;
  98         case 1:
  99                 errno = 0;
 100                 denom = strtod(*argv, &ep);
 101                 if (errno == ERANGE)
 102                         err(1, "%s", *argv);
 103                 if (denom == 0 || *ep != '\0')
 104                         errx(1, "denominator is not valid.");
 105                 break;
 106         default:
 107                 usage();
 108                 /* NOTREACHED */
 109         }
 110
 111         (void)gettimeofday(&tp, NULL);
 112         srandom((u_int)(tp.tv_usec + tp.tv_sec + getpid()));
 113
 114         /* Compute a random exit status between 0 and denom - 1. */
 115         if (random_exit)
 116                 return ((denom * random()) / MAXRANDOM);
 117
 118         /*
 119          * Act as a filter, randomly choosing lines of the standard input
 120          * to write to the standard output.
 121          */
 122         if (unbuffer_output)
 123                 setbuf(stdout, NULL);
 124
 125         /*
 126          * Select whether to print the first line.  (Prime the pump.)
 127          * We find a random number between 0 and denom - 1 and, if it's
 128          * 0 (which has a 1 / denom chance of being true), we select the
 129          * line.
 130          */
 131         selected = (int)(denom * random() / MAXRANDOM) == 0;
 132         while ((ch = getchar()) != EOF) {
 133                 if (selected)
 134                         (void)putchar(ch);
 135                 if (ch == '\n') {
 136                         /* End of that line.  See if we got an error. */
 137                         if (ferror(stdout))
 138                                 err(2, "stdout");
 139
 140                         /* Now see if the next line is to be printed. */
 141                         selected = (int)(denom * random() / MAXRANDOM) == 0;
 142                 }
 143         }
 144         if (ferror(stdin))
 145                 err(2, "stdin");
 146         exit (0);
 147 }
 148
 149 void
 150 usage()
 151 {
 152
 153         (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
 154         exit(1);
 155 }