--- /dev/null
+.\" $NetBSD: shuffle.1,v 1.8 2009/02/19 10:08:15 wiz Exp $
+.\"
+.\" Copyright (c) 1998
+.\" Perry E. Metzger. 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. All advertising materials mentioning features or use of this software
+.\" must display the following acknowledgment:
+.\" This product includes software developed for the NetBSD Project
+.\" by Perry E. Metzger.
+.\" 4. The name of the author may not be used to endorse or promote products
+.\" derived from this software without specific prior written permission.
+.\"
+.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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.
+.\"
+.\"
+.Dd February 18, 2009
+.Dt SHUFFLE 1
+.Os
+.Sh NAME
+.Nm shuffle
+.Nd print a random permutation of the command line arguments
+.Sh SYNOPSIS
+.Nm
+.Op Fl 0
+.Op Fl f Ar filename ...
+.Op Fl n Ar number
+.Op Fl p Ar number
+.Op Ar arg
+.Op Ar ...
+.Sh DESCRIPTION
+The
+.Nm
+program prints a random permutation (or
+.Dq shuffle )
+of its command line arguments.
+This can be useful in shell scripts for selecting a
+random order in which to do a set of tasks, view a set of files, etc.
+.Pp
+If the
+.Fl f
+option is given, the data is taken from that files' contents or if the
+filename is
+.Ar -
+.Dq stdin .
+.Pp
+If the
+.Fl n
+option is given, its argument is treated as a number, and the program
+prints a random permutation of the numbers greater than or equal to 0
+and less than the argument.
+.Pp
+If the
+.Fl p
+option is given, its argument is treated as a number, and the program
+prints that number of randomly selected lines or arguments in a random order.
+.Pp
+The
+.Fl 0
+option changes the field separator character from \en to \e0, so that
+the output is suitable to be sent to
+.Xr xargs 1
+(to handle filenames with whitespace in them).
+.Sh EXAMPLES
+.Bd -literal -offset indent
+$ shuffle a b c d
+c
+b
+d
+a
+$ shuffle -p 1 a b c d
+d
+$ shuffle -n 4 -p 2
+0
+3
+.Ed
+.Sh SEE ALSO
+.Xr jot 1 ,
+.Xr random 6
+.Sh HISTORY
+The
+.Nm
+program first appeared in
+.Nx 1.4 .
+.Sh AUTHORS
+Written by
+.An Perry E. Metzger
+.Aq perry@piermont.com .
--- /dev/null
+/* $NetBSD: shuffle.c,v 1.21 2011/09/16 15:39:29 joerg Exp $ */
+
+/*
+ * Copyright (c) 1998
+ * Perry E. Metzger. 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. All advertising materials mentioning features or use of this software
+ * must display the following acknowledgment:
+ * This product includes software developed for the NetBSD Project
+ * by Perry E. Metzger.
+ * 4. The name of the author may not be used to endorse or promote products
+ * derived from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``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 AUTHOR 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
+__RCSID("$NetBSD: shuffle.c,v 1.21 2011/09/16 15:39:29 joerg Exp $");
+#endif /* not lint */
+
+#include <sys/time.h>
+
+#include <err.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <util.h>
+
+static size_t *get_shuffle(size_t);
+__dead static void usage(void);
+static void get_lines(const char *, char ***, size_t *);
+static size_t get_number(const char *, int);
+
+/*
+ * get_shuffle --
+ * Construct a random shuffle array of t elements
+ */
+static size_t *
+get_shuffle(size_t t)
+{
+ size_t *shuffle;
+ size_t i, j, k, temp;
+
+ shuffle = emalloc(t * sizeof(size_t));
+
+ for (i = 0; i < t; i++)
+ shuffle[i] = i;
+
+ /*
+ * This algorithm taken from Knuth, Seminumerical Algorithms,
+ * 2nd Ed., page 139.
+ */
+
+ for (j = t - 1; j > 0; j--) {
+ k = arc4random() % (j + 1);
+ temp = shuffle[j];
+ shuffle[j] = shuffle[k];
+ shuffle[k] = temp;
+ }
+
+ return shuffle;
+}
+
+/*
+ * usage --
+ * Print a usage message and exit
+ */
+static void
+usage(void)
+{
+
+ (void) fprintf(stderr,
+ "usage: %s [-0] [-f <filename>] [-n <number>] [-p <number>] [<arg> ...]\n",
+ getprogname());
+ exit(1);
+}
+
+
+/*
+ * get_lines --
+ * Return an array of lines read from input
+ */
+static void
+get_lines(const char *fname, char ***linesp, size_t *nlinesp)
+{
+ FILE *fp;
+ char *line;
+ size_t size, nlines = 0, maxlines = 128;
+ char **lines = emalloc(sizeof(char *) * maxlines);
+
+ if (strcmp(fname, "-") == 0)
+ fp = stdin;
+ else
+ if ((fp = fopen(fname, "r")) == NULL)
+ err(1, "Cannot open `%s'", fname);
+
+ while ((line = fgetln(fp, &size)) != NULL) {
+ if (size > 0 && line[size - 1] == '\n')
+ size--;
+ lines[nlines] = emalloc(size + 1);
+ (void)memcpy(lines[nlines], line, size);
+ lines[nlines++][size] = '\0';
+ if (nlines >= maxlines) {
+ maxlines *= 2;
+ lines = erealloc(lines, (sizeof(char *) * maxlines));
+ }
+ }
+ lines[nlines] = NULL;
+
+ *linesp = lines;
+ *nlinesp = nlines;
+ if (strcmp(fname, "-") != 0)
+ (void)fclose(fp);
+}
+
+/*
+ * get_number --
+ * Return a number or exit on error
+ */
+static size_t
+get_number(const char *str, int ch)
+{
+ char *estr;
+ long number;
+
+ errno = 0;
+ number = strtol(str, &estr, 0);
+ if ((number == LONG_MIN || number == LONG_MAX) && errno == ERANGE)
+ err(1, "bad -%c argument `%s'", ch, str);
+ if (*estr)
+ errx(1, "non numeric -%c argument `%s'", ch, str);
+ if (number < 0)
+ errx(1, "negative -%c argument `%s'", ch, str);
+ return (size_t) number;
+}
+
+int
+main(int argc, char *argv[])
+{
+ int nflag = 0, pflag = 0, ch;
+ char *fname = NULL;
+ size_t *shuffle = NULL;
+ char **lines = NULL;
+ size_t nlines = 0, pick = 0, i;
+ char sep = '\n';
+
+ while ((ch = getopt(argc, argv, "0f:n:p:")) != -1) {
+ switch(ch) {
+ case '0':
+ sep = '\0';
+ break;
+ case 'f':
+ fname = optarg;
+ break;
+ case 'n':
+ nlines = get_number(optarg, ch);
+ nflag = 1;
+ break;
+ case 'p':
+ pick = get_number(optarg, ch);
+ pflag = 1;
+ break;
+ case '?':
+ default:
+ usage();
+ }
+ }
+ argc -= optind;
+ argv += optind;
+
+ if ((fname && nflag) || (nflag && (argc > 0)))
+ usage();
+
+ if (fname != NULL)
+ get_lines(fname, &lines, &nlines);
+ else if (nflag == 0) {
+ lines = argv;
+ nlines = argc;
+ }
+
+ if (nlines > 0)
+ shuffle = get_shuffle(nlines);
+
+ if (pflag) {
+ if (pick > nlines)
+ errx(1, "-p specified more components than exist.");
+ nlines = pick;
+ }
+
+ for (i = 0; i < nlines; i++) {
+ if (nflag)
+ printf("%ld", (long)shuffle[i]);
+ else
+ printf("%s", lines[shuffle[i]]);
+ putc(sep, stdout);
+ }
+
+ return 0;
+}