--- /dev/null
+.\" $NetBSD: random.6,v 1.7 2007/03/20 16:12:40 hubertf Exp $
+.\"
+.\" Copyright (c) 1994
+.\" The Regents of the University of California. All rights reserved.
+.\"
+.\" 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.
+.\"
+.\" @(#)random.6 8.2 (Berkeley) 3/31/94
+.\"
+.Dd March 20, 2007
+.Dt RANDOM 6
+.Os
+.Sh NAME
+.Nm random
+.Nd random lines from a file or random numbers
+.Sh SYNOPSIS
+.Nm
+.Op Fl er
+.Op Ar denominator
+.Sh DESCRIPTION
+.Nm
+reads lines from the standard input and copies them to the standard
+output with a probability of 1/denominator.
+The default value for
+.Ar denominator
+is 2.
+.Pp
+The options are as follows:
+.Bl -tag -width Ds
+.It Fl e
+If the
+.Fl e
+option is specified,
+.Nm
+does not read or write anything, and simply exits with a random
+exit value of 0 to
+.Ar denominator Ns -1 ,
+inclusive.
+.It Fl r
+The
+.Fl r
+option guarantees that the output is unbuffered.
+.El
+.Sh SEE ALSO
+.Xr shuffle 1 ,
+.Xr fortune 6
--- /dev/null
+/* $NetBSD: random.c,v 1.14 2009/08/12 08:27:24 dholland 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 <sys/cdefs.h>
+#ifndef lint
+__COPYRIGHT("@(#) Copyright (c) 1994\
+ The Regents of the University of California. All rights reserved.");
+#endif /* not lint */
+
+#ifndef lint
+#if 0
+static char sccsid[] = "@(#)random.c 8.6 (Berkeley) 6/1/94";
+#else
+__RCSID("$NetBSD: random.c,v 1.14 2009/08/12 08:27:24 dholland Exp $");
+#endif
+#endif /* not lint */
+
+#include <sys/types.h>
+#include <sys/time.h>
+
+#include <err.h>
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <limits.h>
+
+static void usage(void) __dead;
+
+int
+main(int argc, char *argv[])
+{
+ struct timeval tp;
+ double denom;
+ int ch, random_exit, selected, unbuffer_output;
+ char *ep;
+
+ denom = 0;
+ random_exit = unbuffer_output = 0;
+ while ((ch = getopt(argc, argv, "er")) != -1)
+ switch (ch) {
+ case 'e':
+ random_exit = 1;
+ break;
+ case 'r':
+ unbuffer_output = 1;
+ break;
+ default:
+ case '?':
+ usage();
+ /* NOTREACHED */
+ }
+
+ 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();
+ /* NOTREACHED */
+ }
+
+ (void)gettimeofday(&tp, NULL);
+ srandom((unsigned long)tp.tv_usec + tp.tv_sec + getpid());
+
+ /* Compute a random exit status between 0 and denom - 1. */
+ if (random_exit)
+ return ((denom * random()) / RANDOM_MAX);
+
+ /*
+ * Act as a filter, randomly choosing lines of the standard input
+ * to write to the standard output.
+ */
+ if (unbuffer_output)
+ setbuf(stdout, NULL);
+
+ /*
+ * 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 = (int)(denom * random() / RANDOM_MAX) == 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 = (int)(denom * random() / RANDOM_MAX) == 0;
+ }
+ }
+ if (ferror(stdin))
+ err(2, "stdin");
+ exit (0);
+
+ return 0;
+}
+
+static void
+usage(void)
+{
+
+ (void)fprintf(stderr, "usage: random [-er] [denominator]\n");
+ exit(1);
+}