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/* $OpenBSD: random.c,v 1.20 2016/03/07 12:07:56 mestre Exp $ */
/* $NetBSD: random.c,v 1.3 1995/04/22 07:44:05 cgd Exp $ */
/*
* Copyright (c) 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Guy Harris at Network Appliance Corp.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <err.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
__dead void usage(void);
int
main(int argc, char *argv[])
{
double denom;
int ch, random_exit, selected, unbuffer_output;
char *ep;
if (pledge("stdio", NULL) == -1)
err(1, "pledge");
random_exit = unbuffer_output = 0;
while ((ch = getopt(argc, argv, "erh")) != -1)
switch (ch) {
case 'e':
random_exit = 1;
break;
case 'r':
unbuffer_output = 1;
break;
default:
case 'h':
usage();
}
argc -= optind;
argv += optind;
switch (argc) {
case 0:
denom = 2;
break;
case 1:
errno = 0;
denom = strtod(*argv, &ep);
if (errno == ERANGE)
err(1, "%s", *argv);
if (denom == 0 || *ep != '\0')
errx(1, "denominator is not valid.");
break;
default:
usage();
}
/* Compute a random exit status between 0 and denom - 1. */
if (random_exit)
return (arc4random_uniform(denom));
/*
* Act as a filter, randomly choosing lines of the standard input
* to write to the standard output.
*/
if (unbuffer_output)
setvbuf(stdout, NULL, _IONBF, 0);
/*
* Select whether to print the first line. (Prime the pump.)
* We find a random number between 0 and denom - 1 and, if it's
* 0 (which has a 1 / denom chance of being true), we select the
* line.
*/
selected = arc4random_uniform(denom) == 0;
while ((ch = getchar()) != EOF) {
if (selected)
(void)putchar(ch);
if (ch == '\n') {
/* End of that line. See if we got an error. */
if (ferror(stdout))
err(2, "stdout");
/* Now see if the next line is to be printed. */
selected = arc4random_uniform(denom) == 0;
}
}
if (ferror(stdin))
err(2, "stdin");
return 0;
}
void
usage(void)
{
(void)fprintf(stderr, "usage: %s [-er] [denominator]\n", getprogname());
exit(1);
}
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