tangetools/rand/rand
2017-06-28 13:21:31 +02:00

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#!/bin/bash
: <<=cut
=pod
=head1 NAME
rand - Generate (pseudo-)random data
=head1 SYNOPSIS
B<rand> [[I<from>] I<to>]
=head1 DESCRIPTION
B<rand> uses B<openssl> to generate pseudorandom data. Just like B<cat
/dev/urandom> it generates an infinite amount of data, but it is much
faster (400 MB/s on hardware from 2013).
The quality is lower as there are only 2^256 different tables (this is
still around the number of atoms in the visible universe).
If I<to> is given, numbers will be integers from 0 to I<to>.
If I<from> is also given, numbers will be integers from I<from> to I<to>.
=head1 EXAMPLE
Overwrite a harddisk with random data:
rand >/dev/sda
=head1 EXAMPLE
100 random numbers from 1000 to 1999:
rand 1000 1999 | head -n 100
=head1 AUTHOR
Copyright (C) 2017 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.
=head1 LICENSE
Copyright (C) 2012 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
at your option any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
=head1 DEPENDENCIES
B<rand> uses B<openssl>.
=head1 SEE ALSO
B<openssl>
=cut
# Generate random 8-bit data by AES encrypting /dev/zero with a random
# key
randfunc() {
key=$(openssl rand -hex 16)
iv=$(openssl rand -hex 16)
< /dev/zero openssl enc -aes-128-ctr -K $key -iv $iv 2>/dev/null
}
export -f randfunc
ints() {
from=$1
to=$2
# Allow up to 2^64
perl -e '$diff='$to-$from'+1;
$factor = 2**64/$diff;
while(sysread(STDIN,$buf,65536)) {
print map { (int($_ / $factor) + '$from'),"\n" } unpack("Q*",$buf);
}'
}
export -f ints
randints() {
randfunc | ints "$@"
}
export -f randints
if [ "$1" == "" ] ; then
# Boost performance by running 1 per CPU core
eval parallel -u randfunc ::: {1..$(parallel --number-of-cores)}
else
# $1 set => numerical
if [ "$2" == "" ] ; then
# 0 .. $1
eval parallel --lb randints 0 $1 ::: {1..$(parallel --number-of-cores)}
else
# $1 .. $2
eval parallel --lb randints $1 $2 ::: {1..$(parallel --number-of-cores)}
fi
fi