1 /* $OpenBSD: random.c,v 1.20 2016/03/07 12:07:56 mestre Exp $ */ 2 /* $NetBSD: random.c,v 1.3 1995/04/22 07:44:05 cgd Exp $ */ 3 4 /* 5 * Copyright (c) 1994 6 * The Regents of the University of California. All rights reserved. 7 * 8 * This code is derived from software contributed to Berkeley by 9 * Guy Harris at Network Appliance Corp. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 */ 35 36 #include <err.h> 37 #include <errno.h> 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <unistd.h> 41 42 __dead void usage(void); 43 44 int 45 main(int argc, char *argv[]) 46 { 47 double denom; 48 int ch, random_exit, selected, unbuffer_output; 49 char *ep; 50 51 if (pledge("stdio", NULL) == -1) 52 err(1, "pledge"); 53 54 random_exit = unbuffer_output = 0; 55 while ((ch = getopt(argc, argv, "erh")) != -1) 56 switch (ch) { 57 case 'e': 58 random_exit = 1; 59 break; 60 case 'r': 61 unbuffer_output = 1; 62 break; 63 default: 64 case 'h': 65 usage(); 66 } 67 68 argc -= optind; 69 argv += optind; 70 71 switch (argc) { 72 case 0: 73 denom = 2; 74 break; 75 case 1: 76 errno = 0; 77 denom = strtod(*argv, &ep); 78 if (errno == ERANGE) 79 err(1, "%s", *argv); 80 if (denom == 0 || *ep != '\0') 81 errx(1, "denominator is not valid."); 82 break; 83 default: 84 usage(); 85 } 86 87 /* Compute a random exit status between 0 and denom - 1. */ 88 if (random_exit) 89 return (arc4random_uniform(denom)); 90 91 /* 92 * Act as a filter, randomly choosing lines of the standard input 93 * to write to the standard output. 94 */ 95 if (unbuffer_output) 96 setvbuf(stdout, NULL, _IONBF, 0); 97 98 /* 99 * Select whether to print the first line. (Prime the pump.) 100 * We find a random number between 0 and denom - 1 and, if it's 101 * 0 (which has a 1 / denom chance of being true), we select the 102 * line. 103 */ 104 selected = arc4random_uniform(denom) == 0; 105 while ((ch = getchar()) != EOF) { 106 if (selected) 107 (void)putchar(ch); 108 if (ch == '\n') { 109 /* End of that line. See if we got an error. */ 110 if (ferror(stdout)) 111 err(2, "stdout"); 112 113 /* Now see if the next line is to be printed. */ 114 selected = arc4random_uniform(denom) == 0; 115 } 116 } 117 if (ferror(stdin)) 118 err(2, "stdin"); 119 return 0; 120 } 121 122 void 123 usage(void) 124 { 125 126 (void)fprintf(stderr, "usage: %s [-er] [denominator]\n", getprogname()); 127 exit(1); 128 } 129