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 } 158