1 /* $NetBSD: random.c,v 1.16 2021/05/02 12:50:46 rillig 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. Neither the name of the University nor the names of its contributors
19 * may be used to endorse or promote products derived from this software
20 * without specific prior written permission.
21 *
22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 * SUCH DAMAGE.
33 */
34
35 #include <sys/cdefs.h>
36 #ifndef lint
37 __COPYRIGHT("@(#) Copyright (c) 1994\
38 The Regents of the University of California. All rights reserved.");
39 #endif /* not lint */
40
41 #ifndef lint
42 #if 0
43 static char sccsid[] = "@(#)random.c 8.6 (Berkeley) 6/1/94";
44 #else
45 __RCSID("$NetBSD: random.c,v 1.16 2021/05/02 12:50:46 rillig Exp $");
46 #endif
47 #endif /* not lint */
48
49 #include <sys/types.h>
50 #include <sys/time.h>
51
52 #include <err.h>
53 #include <errno.h>
54 #include <stdio.h>
55 #include <stdlib.h>
56 #include <time.h>
57 #include <unistd.h>
58 #include <limits.h>
59
60 static void usage(void) __dead;
61
62 int
main(int argc,char * argv[])63 main(int argc, char *argv[])
64 {
65 double denom;
66 int ch, random_exit, selected, unbuffer_output;
67 char *ep;
68
69 denom = 0;
70 random_exit = unbuffer_output = 0;
71 while ((ch = getopt(argc, argv, "er")) != -1)
72 switch (ch) {
73 case 'e':
74 random_exit = 1;
75 break;
76 case 'r':
77 unbuffer_output = 1;
78 break;
79 default:
80 case '?':
81 usage();
82 /* NOTREACHED */
83 }
84
85 argc -= optind;
86 argv += optind;
87
88 switch (argc) {
89 case 0:
90 denom = 2;
91 break;
92 case 1:
93 errno = 0;
94 denom = strtod(*argv, &ep);
95 if (errno == ERANGE)
96 err(1, "%s", *argv);
97 if (denom == 0 || *ep != '\0')
98 errx(1, "denominator is not valid.");
99 break;
100 default:
101 usage();
102 /* NOTREACHED */
103 }
104
105 /* Compute a random exit status between 0 and denom - 1. */
106 if (random_exit)
107 return arc4random_uniform(denom);
108
109 /*
110 * Act as a filter, randomly choosing lines of the standard input
111 * to write to the standard output.
112 */
113 if (unbuffer_output)
114 setbuf(stdout, NULL);
115
116 /*
117 * Select whether to print the first line. (Prime the pump.)
118 * We find a random number between 0 and denom - 1 and, if it's
119 * 0 (which has a 1 / denom chance of being true), we select the
120 * line.
121 */
122 selected = (arc4random_uniform(denom) == 0);
123 while ((ch = getchar()) != EOF) {
124 if (selected)
125 (void)putchar(ch);
126 if (ch == '\n') {
127 /* End of that line. See if we got an error. */
128 if (ferror(stdout))
129 err(2, "stdout");
130
131 /* Now see if the next line is to be printed. */
132 selected = (arc4random_uniform(denom) == 0);
133 }
134 }
135 if (ferror(stdin))
136 err(2, "stdin");
137 exit (0);
138
139 return 0;
140 }
141
142 static void
usage(void)143 usage(void)
144 {
145
146 (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
147 exit(1);
148 }
149