random.c revision 54482 
1/*
2 * Copyright (c) 1994
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Guy Harris at Network Appliance Corp.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#ifndef lint
38static const char copyright[] =
39"@(#) Copyright (c) 1994\n\
40	The Regents of the University of California.  All rights reserved.\n";
41#endif /* not lint */
42
43#ifndef lint
44#if 0
45static char sccsid[] = "@(#)random.c	8.5 (Berkeley) 4/5/94";
46#endif
47static const char rcsid[] =
48 "$FreeBSD: head/games/random/random.c 54482 1999-12-12 06:30:46Z billf $";
49#endif /* not lint */
50
51#include <sys/types.h>
52
53#include <err.h>
54#include <errno.h>
55#include <limits.h>
56#include <stdio.h>
57#include <stdlib.h>
58#include <time.h>
59#include <unistd.h>
60
61void usage __P((void));
62
63int
64main(argc, argv)
65	int argc;
66	char *argv[];
67{
68	double denom;
69	int ch, random_exit, selected, unbuffer_output;
70	char *ep;
71
72	random_exit = unbuffer_output = 0;
73	denom = 0;
74	while ((ch = getopt(argc, argv, "er")) != -1)
75		switch (ch) {
76		case 'e':
77			random_exit = 1;
78			break;
79		case 'r':
80			unbuffer_output = 1;
81			break;
82		default:
83		case '?':
84			usage();
85			/* NOTREACHED */
86		}
87
88	argc -= optind;
89	argv += optind;
90
91	switch (argc) {
92	case 0:
93		denom = 2;
94		break;
95	case 1:
96		errno = 0;
97		denom = strtod(*argv, &ep);
98		if (errno == ERANGE)
99			err(1, "%s", *argv);
100		if (denom <= 0 || *ep != '\0')
101			errx(1, "denominator is not valid.");
102		if (random_exit && denom > 255)
103			errx(1, "denominator must be <= 255 for random exit.");
104		break;
105	default:
106		usage();
107		/* NOTREACHED */
108	}
109
110	srandomdev();
111
112	/* Compute a random exit status between 0 and denom - 1. */
113	if (random_exit)
114		return ((denom * random()) / LONG_MAX);
115
116	/*
117	 * Act as a filter, randomly choosing lines of the standard input
118	 * to write to the standard output.
119	 */
120	if (unbuffer_output)
121		setbuf(stdout, NULL);
122
123	/*
124	 * Select whether to print the first line.  (Prime the pump.)
125	 * We find a random number between 0 and denom - 1 and, if it's
126	 * 0 (which has a 1 / denom chance of being true), we select the
127	 * line.
128	 */
129	selected = (int)(denom * random() / LONG_MAX) == 0;
130	while ((ch = getchar()) != EOF) {
131		if (selected)
132			(void)putchar(ch);
133		if (ch == '\n') {
134			/* End of that line.  See if we got an error. */
135			if (ferror(stdout))
136				err(2, "stdout");
137
138			/* Now see if the next line is to be printed. */
139			selected = (int)(denom * random() / LONG_MAX) == 0;
140		}
141	}
142	if (ferror(stdin))
143		err(2, "stdin");
144	exit (0);
145}
146
147void
148usage()
149{
150
151	(void)fprintf(stderr, "usage: random [-er] [denominator]\n");
152	exit(1);
153}
154