185 lines
3.9 KiB
Bash
Executable file
185 lines
3.9 KiB
Bash
Executable file
#!/bin/bash
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: <<=cut
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=pod
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=head1 NAME
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rand - generate (pseudo-)random data
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=head1 SYNOPSIS
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B<rand> [-f FORMAT|--format FORMAT] [-s SEED|--seed SEED] [[I<from>] I<to>]
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=head1 DESCRIPTION
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B<rand> uses B<openssl> to generate pseudorandom data. Just like B<cat
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/dev/urandom> it generates an infinite amount of data, but it is much
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faster (400 MB/s on hardware from 2013).
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The quality is lower as there are only 2^256 different tables (this is
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still around the number of atoms in the visible universe).
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If I<to> is given, numbers will be integers from 0 to I<to>.
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If I<from> is also given, numbers will be integers from I<from> to I<to>.
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=head1 OPTIONS
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=over 4
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=item B<--format> I<FORMAT>
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=item B<-f> I<FORMAT>
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Format number using I<FORMAT>. I<FORMAT> follows B<printf>s specification.
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=item B<--seed> I<SEED>
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=item B<-s> I<SEED>
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Use SEED for random number generator for reproducible numbers.
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=back
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=head1 EXAMPLE
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Overwrite a harddisk with random data:
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rand >/dev/sda
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=head1 EXAMPLE
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100 random numbers from 1000 to 1999:
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rand 1000 1999 | head -n 100
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=head1 EXAMPLE
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100 random numbers from 256 to 65535 in hex with 0s prepended:
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rand -f '%04x\n' 256 65535 | head -n 100
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=head1 AUTHOR
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Copyright (C) 2017-2020 Ole Tange,
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http://ole.tange.dk and Free Software Foundation, Inc.
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=head1 LICENSE
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Copyright (C) 2012 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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at your option any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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=head1 DEPENDENCIES
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B<rand> uses B<openssl>, B<perl>, and B<parallel>.
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=head1 SEE ALSO
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B<openssl>
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=cut
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randdata() {
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# Generate random 8-bit data by AES encrypting /dev/zero
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if [ "$seed" == "" ] ; then
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# use a random key
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key=$(openssl rand -hex 16)
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iv=$(openssl rand -hex 16)
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else
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# use seed from --seed
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key=$(echo "$seed" | openssl sha256 -hex | cut -d' ' -f2)
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iv=$(echo "$seed" | openssl sha512 -hex | cut -d' ' -f2)
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fi
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< /dev/zero openssl enc -aes-128-ctr -K $key -iv $iv 2>/dev/null
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}
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export -f randdata
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ints() {
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# Convert random data on stdin to numbers $from..$to in $fmt
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from=$1
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to=$2
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fmt="$3"
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# Allow up to 2^64
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perl -e '$diff='$to-$from'+1;
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$factor = 2**64/$diff;
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while(sysread(STDIN,$buf,65536)) {
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print map { sprintf("'"$fmt"'", int($_ / $factor) + '$from'); } unpack("Q*",$buf);
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}'
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}
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export -f ints
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randints() {
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randdata | ints "$@"
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}
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export -f randints
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# Default format of ints
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fmt='%s\n'
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while true; do
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case "$1" in
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-f | --fmt ) fmt="$2"; shift 2 ;;
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-s | --seed ) seed="$2"; shift 2 ;;
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-D | --debug ) debug=true; shift ;;
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-h | --help ) help=1; shift 2 ;;
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-- ) shift; break ;;
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* ) break ;;
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esac
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done
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qfmt="$(parallel --shellquote --shellquote ::: "$fmt")"
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if [ "$seed" == "" ] ; then
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if [ "$1" == "" ] ; then
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# Boost performance by running 1 per CPU core
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eval parallel -u randdata ::: {1..$(parallel --number-of-threads)}
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else
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# $1 set => numerical
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if [ "$2" == "" ] ; then
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# 0 .. $1
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eval parallel -N0 --lb randints 0 $1 "$qfmt" ::: {1..$(parallel --number-of-threads)}
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else
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# $1 .. $2
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eval parallel -N0 --lb randints $1 $2 "$qfmt" ::: {1..$(parallel --number-of-threads)}
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fi
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fi
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else
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if [ "$1" == "" ] ; then
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# Run a single instance
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randdata
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else
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# $1 set => numerical
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if [ "$2" == "" ] ; then
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# 0 .. $1
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randints 0 $1 "$fmt"
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else
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# $1 .. $2
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randints $1 $2 "$fmt"
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fi
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fi
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fi
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