Home | History | Annotate | Line # | Download | only in random
random.c revision 1.13 
      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 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 void
    147 usage(void)
    148 {
    149 
    150 	(void)fprintf(stderr, "usage: random [-er] [denominator]\n");
    151 	exit(1);
    152 }
    153