random.c revision 8856
12490Sjkh/* 22490Sjkh * Copyright (c) 1994 32490Sjkh * The Regents of the University of California. All rights reserved. 42490Sjkh * 52490Sjkh * This code is derived from software contributed to Berkeley by 62490Sjkh * Guy Harris at Network Appliance Corp. 72490Sjkh * 82490Sjkh * Redistribution and use in source and binary forms, with or without 92490Sjkh * modification, are permitted provided that the following conditions 102490Sjkh * are met: 112490Sjkh * 1. Redistributions of source code must retain the above copyright 122490Sjkh * notice, this list of conditions and the following disclaimer. 132490Sjkh * 2. Redistributions in binary form must reproduce the above copyright 142490Sjkh * notice, this list of conditions and the following disclaimer in the 152490Sjkh * documentation and/or other materials provided with the distribution. 162490Sjkh * 3. All advertising materials mentioning features or use of this software 172490Sjkh * must display the following acknowledgement: 182490Sjkh * This product includes software developed by the University of 192490Sjkh * California, Berkeley and its contributors. 202490Sjkh * 4. Neither the name of the University nor the names of its contributors 212490Sjkh * may be used to endorse or promote products derived from this software 222490Sjkh * without specific prior written permission. 232490Sjkh * 242490Sjkh * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 252490Sjkh * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 262490Sjkh * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 272490Sjkh * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 282490Sjkh * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 292490Sjkh * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 302490Sjkh * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 312490Sjkh * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 322490Sjkh * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 332490Sjkh * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 342490Sjkh * SUCH DAMAGE. 352490Sjkh */ 362490Sjkh 372490Sjkh#ifndef lint 382490Sjkhstatic char copyright[] = 392490Sjkh"@(#) Copyright (c) 1994\n\ 402490Sjkh The Regents of the University of California. All rights reserved.\n"; 412490Sjkh#endif /* not lint */ 422490Sjkh 432490Sjkh#ifndef lint 442490Sjkhstatic char sccsid[] = "@(#)random.c 8.5 (Berkeley) 4/5/94"; 452490Sjkh#endif /* not lint */ 462490Sjkh 472490Sjkh#include <sys/types.h> 482490Sjkh 492490Sjkh#include <err.h> 502490Sjkh#include <errno.h> 516160Sbde#include <limits.h> 522490Sjkh#include <stdio.h> 532490Sjkh#include <stdlib.h> 542490Sjkh#include <time.h> 552490Sjkh#include <unistd.h> 562490Sjkh 572490Sjkhvoid usage __P((void)); 582490Sjkh 592490Sjkhint 602490Sjkhmain(argc, argv) 612490Sjkh int argc; 622490Sjkh char *argv[]; 632490Sjkh{ 642490Sjkh extern int optind; 652490Sjkh time_t now; 662490Sjkh double denom; 672490Sjkh int ch, random_exit, selected, unbuffer_output; 682490Sjkh char *ep; 692490Sjkh 702490Sjkh random_exit = unbuffer_output = 0; 712490Sjkh while ((ch = getopt(argc, argv, "er")) != EOF) 722490Sjkh switch (ch) { 732490Sjkh case 'e': 742490Sjkh random_exit = 1; 752490Sjkh break; 762490Sjkh case 'r': 772490Sjkh unbuffer_output = 1; 782490Sjkh break; 792490Sjkh default: 802490Sjkh case '?': 812490Sjkh usage(); 822490Sjkh /* NOTREACHED */ 832490Sjkh } 842490Sjkh 852490Sjkh argc -= optind; 862490Sjkh argv += optind; 872490Sjkh 882490Sjkh switch (argc) { 892490Sjkh case 0: 902490Sjkh denom = 2; 912490Sjkh break; 922490Sjkh case 1: 932490Sjkh errno = 0; 942490Sjkh denom = strtod(*argv, &ep); 952490Sjkh if (errno == ERANGE) 962490Sjkh err(1, "%s", *argv); 972490Sjkh if (denom == 0 || *ep != '\0') 982490Sjkh errx(1, "denominator is not valid."); 992490Sjkh break; 1002490Sjkh default: 1018856Srgrimes usage(); 1022490Sjkh /* NOTREACHED */ 1032490Sjkh } 1042490Sjkh 1052490Sjkh (void)time(&now); 1062490Sjkh srandom((u_int)(now + getpid())); 1072490Sjkh 1082490Sjkh /* Compute a random exit status between 0 and denom - 1. */ 1092490Sjkh if (random_exit) 1102490Sjkh return ((denom * random()) / LONG_MAX); 1112490Sjkh 1122490Sjkh /* 1132490Sjkh * Act as a filter, randomly choosing lines of the standard input 1142490Sjkh * to write to the standard output. 1152490Sjkh */ 1162490Sjkh if (unbuffer_output) 1172490Sjkh setbuf(stdout, NULL); 1188856Srgrimes 1192490Sjkh /* 1202490Sjkh * Select whether to print the first line. (Prime the pump.) 1212490Sjkh * We find a random number between 0 and denom - 1 and, if it's 1222490Sjkh * 0 (which has a 1 / denom chance of being true), we select the 1232490Sjkh * line. 1242490Sjkh */ 1252490Sjkh selected = (int)(denom * random() / LONG_MAX) == 0; 1262490Sjkh while ((ch = getchar()) != EOF) { 1272490Sjkh if (selected) 1282490Sjkh (void)putchar(ch); 1292490Sjkh if (ch == '\n') { 1302490Sjkh /* End of that line. See if we got an error. */ 1312490Sjkh if (ferror(stdout)) 1322490Sjkh err(2, "stdout"); 1332490Sjkh 1342490Sjkh /* Now see if the next line is to be printed. */ 1352490Sjkh selected = (int)(denom * random() / LONG_MAX) == 0; 1362490Sjkh } 1372490Sjkh } 1382490Sjkh if (ferror(stdin)) 1392490Sjkh err(2, "stdin"); 1402490Sjkh exit (0); 1412490Sjkh} 1422490Sjkh 1432490Sjkhvoid 1442490Sjkhusage() 1452490Sjkh{ 1462490Sjkh 1472490Sjkh (void)fprintf(stderr, "usage: random [-er] [denominator]\n"); 1482490Sjkh exit(1); 1492490Sjkh} 150