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 43static 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 60static void usage(void) __dead; 61 62int 63main(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 142static void 143usage(void) 144{ 145 146 (void)fprintf(stderr, "usage: random [-er] [denominator]\n"); 147 exit(1); 148} 149