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      1 /*	$NetBSD: random.c,v 1.16 2021/05/02 12:50:46 rillig 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 1.16 2021/05/02 12:50:46 rillig 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 }
    149