1 /* $NetBSD: random.c,v 1.3 1995/04/22 07:44:05 cgd 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 #ifndef lint 40 static char copyright[] = 41 "@(#) 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 8.5 (Berkeley) 4/5/94"; 48 #else 49 static char rcsid[] = "$NetBSD: random.c,v 1.3 1995/04/22 07:44:05 cgd Exp $"; 50 #endif 51 #endif /* not lint */ 52 53 #include <sys/types.h> 54 55 #include <err.h> 56 #include <errno.h> 57 #include <stdio.h> 58 #include <stdlib.h> 59 #include <time.h> 60 #include <unistd.h> 61 #include <limits.h> 62 63 void usage __P((void)); 64 65 int 66 main(argc, argv) 67 int argc; 68 char *argv[]; 69 { 70 extern int optind; 71 time_t now; 72 double denom; 73 int ch, random_exit, selected, unbuffer_output; 74 char *ep; 75 76 random_exit = unbuffer_output = 0; 77 while ((ch = getopt(argc, argv, "er")) != EOF) 78 switch (ch) { 79 case 'e': 80 random_exit = 1; 81 break; 82 case 'r': 83 unbuffer_output = 1; 84 break; 85 default: 86 case '?': 87 usage(); 88 /* NOTREACHED */ 89 } 90 91 argc -= optind; 92 argv += optind; 93 94 switch (argc) { 95 case 0: 96 denom = 2; 97 break; 98 case 1: 99 errno = 0; 100 denom = strtod(*argv, &ep); 101 if (errno == ERANGE) 102 err(1, "%s", *argv); 103 if (denom == 0 || *ep != '\0') 104 errx(1, "denominator is not valid."); 105 break; 106 default: 107 usage(); 108 /* NOTREACHED */ 109 } 110 111 (void)time(&now); 112 srandom((u_int)(now + getpid())); 113 114 /* Compute a random exit status between 0 and denom - 1. */ 115 if (random_exit) 116 return ((denom * random()) / LONG_MAX); 117 118 /* 119 * Act as a filter, randomly choosing lines of the standard input 120 * to write to the standard output. 121 */ 122 if (unbuffer_output) 123 setbuf(stdout, NULL); 124 125 /* 126 * Select whether to print the first line. (Prime the pump.) 127 * We find a random number between 0 and denom - 1 and, if it's 128 * 0 (which has a 1 / denom chance of being true), we select the 129 * line. 130 */ 131 selected = (int)(denom * random() / LONG_MAX) == 0; 132 while ((ch = getchar()) != EOF) { 133 if (selected) 134 (void)putchar(ch); 135 if (ch == '\n') { 136 /* End of that line. See if we got an error. */ 137 if (ferror(stdout)) 138 err(2, "stdout"); 139 140 /* Now see if the next line is to be printed. */ 141 selected = (int)(denom * random() / LONG_MAX) == 0; 142 } 143 } 144 if (ferror(stdin)) 145 err(2, "stdin"); 146 exit (0); 147 } 148 149 void 150 usage() 151 { 152 153 (void)fprintf(stderr, "usage: random [-er] [denominator]\n"); 154 exit(1); 155 } 156