150 lines
4.0 KiB
C
150 lines
4.0 KiB
C
/*
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* Copyright (c) 1994
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Guy Harris at Network Appliance Corp.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#ifndef lint
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static char copyright[] =
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"@(#) Copyright (c) 1994\n\
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The Regents of the University of California. All rights reserved.\n";
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#endif /* not lint */
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#ifndef lint
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static char sccsid[] = "@(#)random.c 8.5 (Berkeley) 4/5/94";
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#endif /* not lint */
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#include <sys/types.h>
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#include <err.h>
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#include <errno.h>
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#include <limits.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <time.h>
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#include <unistd.h>
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void usage __P((void));
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int
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main(argc, argv)
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int argc;
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char *argv[];
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{
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extern int optind;
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time_t now;
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double denom;
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int ch, random_exit, selected, unbuffer_output;
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char *ep;
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random_exit = unbuffer_output = 0;
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while ((ch = getopt(argc, argv, "er")) != EOF)
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switch (ch) {
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case 'e':
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random_exit = 1;
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break;
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case 'r':
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unbuffer_output = 1;
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break;
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default:
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case '?':
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usage();
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/* NOTREACHED */
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}
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argc -= optind;
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argv += optind;
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switch (argc) {
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case 0:
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denom = 2;
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break;
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case 1:
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errno = 0;
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denom = strtod(*argv, &ep);
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if (errno == ERANGE)
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err(1, "%s", *argv);
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if (denom == 0 || *ep != '\0')
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errx(1, "denominator is not valid.");
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break;
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default:
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usage();
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/* NOTREACHED */
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}
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(void)time(&now);
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srandom((u_int)(now + getpid()));
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/* Compute a random exit status between 0 and denom - 1. */
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if (random_exit)
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return ((denom * random()) / LONG_MAX);
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/*
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* Act as a filter, randomly choosing lines of the standard input
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* to write to the standard output.
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*/
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if (unbuffer_output)
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setbuf(stdout, NULL);
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/*
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* Select whether to print the first line. (Prime the pump.)
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* We find a random number between 0 and denom - 1 and, if it's
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* 0 (which has a 1 / denom chance of being true), we select the
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* line.
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*/
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selected = (int)(denom * random() / LONG_MAX) == 0;
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while ((ch = getchar()) != EOF) {
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if (selected)
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(void)putchar(ch);
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if (ch == '\n') {
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/* End of that line. See if we got an error. */
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if (ferror(stdout))
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err(2, "stdout");
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/* Now see if the next line is to be printed. */
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selected = (int)(denom * random() / LONG_MAX) == 0;
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}
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}
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if (ferror(stdin))
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err(2, "stdin");
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exit (0);
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}
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void
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usage()
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{
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(void)fprintf(stderr, "usage: random [-er] [denominator]\n");
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exit(1);
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}
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