random/random.c

   1 /*      $NetBSD: random.c,v 1.5 1997/10/12 01:14:22 lukem 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. All advertising materials mentioning features or use of this software
  19  *    must display the following acknowledgement:
  20  *      This product includes software developed by the University of
  21  *      California, Berkeley and its contributors.
  22  * 4. Neither the name of the University nor the names of its contributors
  23  *    may be used to endorse or promote products derived from this software
  24  *    without specific prior written permission.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  36  * SUCH DAMAGE.
  37  */
  38
  39 #include <sys/cdefs.h>
  40 #ifndef lint
  41 __COPYRIGHT("@(#) Copyright (c) 1994\n\
  42         The Regents of the University of California.  All rights reserved.\n");
  43 #endif /* not lint */
  44
  45 #ifndef lint
  46 #if 0
  47 static char sccsid[] = "@(#)random.c    8.6 (Berkeley) 6/1/94";
  48 #else
  49 __RCSID("$NetBSD: random.c,v 1.5 1997/10/12 01:14:22 lukem Exp $");
  50 #endif
  51 #endif /* not lint */
  52
  53 #include <sys/types.h>
  54 #include <sys/time.h>
  55
  56 #include <err.h>
  57 #include <errno.h>
  58 #include <stdio.h>
  59 #include <stdlib.h>
  60 #include <time.h>
  61 #include <unistd.h>
  62 #include <limits.h>
  63
  64 int  main __P((int, char **));
  65 void usage __P((void));
  66
  67 int
  68 main(argc, argv)
  69         int argc;
  70         char *argv[];
  71 {
  72         struct timeval tp;
  73         double denom;
  74         int ch, random_exit, selected, unbuffer_output;
  75         char *ep;
  76
  77         denom = 0;
  78         random_exit = unbuffer_output = 0;
  79         while ((ch = getopt(argc, argv, "er")) != -1)
  80                 switch (ch) {
  81                 case 'e':
  82                         random_exit = 1;
  83                         break;
  84                 case 'r':
  85                         unbuffer_output = 1;
  86                         break;
  87                 default:
  88                 case '?':
  89                         usage();
  90                         /* NOTREACHED */
  91                 }
  92
  93         argc -= optind;
  94         argv += optind;
  95
  96         switch (argc) {
  97         case 0:
  98                 denom = 2;
  99                 break;
 100         case 1:
 101                 errno = 0;
 102                 denom = strtod(*argv, &ep);
 103                 if (errno == ERANGE)
 104                         err(1, "%s", *argv);
 105                 if (denom == 0 || *ep != '\0')
 106                         errx(1, "denominator is not valid.");
 107                 break;
 108         default:
 109                 usage();
 110                 /* NOTREACHED */
 111         }
 112
 113         (void)gettimeofday(&tp, NULL);
 114         srandom((u_int)(tp.tv_usec + tp.tv_sec + getpid()));
 115
 116         /* Compute a random exit status between 0 and denom - 1. */
 117         if (random_exit)
 118                 return ((denom * random()) / LONG_MAX);
 119
 120         /*
 121          * Act as a filter, randomly choosing lines of the standard input
 122          * to write to the standard output.
 123          */
 124         if (unbuffer_output)
 125                 setbuf(stdout, NULL);
 126
 127         /*
 128          * Select whether to print the first line.  (Prime the pump.)
 129          * We find a random number between 0 and denom - 1 and, if it's
 130          * 0 (which has a 1 / denom chance of being true), we select the
 131          * line.
 132          */
 133         selected = (int)(denom * random() / LONG_MAX) == 0;
 134         while ((ch = getchar()) != EOF) {
 135                 if (selected)
 136                         (void)putchar(ch);
 137                 if (ch == '\n') {
 138                         /* End of that line.  See if we got an error. */
 139                         if (ferror(stdout))
 140                                 err(2, "stdout");
 141
 142                         /* Now see if the next line is to be printed. */
 143                         selected = (int)(denom * random() / LONG_MAX) == 0;
 144                 }
 145         }
 146         if (ferror(stdin))
 147                 err(2, "stdin");
 148         exit (0);
 149 }
 150
 151 void
 152 usage()
 153 {
 154
 155         (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
 156         exit(1);
 157 }