1 /* $NetBSD: random.c,v 1.14 2009/08/12 08:27:24 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 1.14 2009/08/12 08:27:24 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 static 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 static void 147 usage(void) 148 { 149 150 (void)fprintf(stderr, "usage: random [-er] [denominator]\n"); 151 exit(1); 152 } 153