
			     GNU Parallel

		https://www.gnu.org/software/parallel/


= Presentation of GNU Parallel =

GNU Parallel is a shell tool for executing jobs in parallel using one
or more computers. A job can be a single command or a small script
that has to be run for each of the lines in the input. The typical
input is a list of files, a list of hosts, a list of users, a list of
URLs, or a list of tables. A job can also be a command that reads from
a pipe. GNU Parallel can then split the input and pipe it into
commands in parallel.

If you use xargs and tee today you will find GNU Parallel very easy to
use as GNU Parallel is written to have the same options as xargs. If
you write loops in shell, you will find GNU Parallel may be able to
replace most of the loops and make them run faster by running several
jobs in parallel.

GNU Parallel makes sure output from the commands is the same output as
you would get had you run the commands sequentially. This makes it
possible to use output from GNU Parallel as input for other programs.

See the cheat sheet for examples that cover most of the daily usage:
www.gnu.org/s/parallel/parallel_cheat.pdf


= 10 seconds installation =

For security reasons it is recommended you use your package manager to
install. But if you cannot do that then you can use this 10 seconds
installation.

The 10 seconds installation will try to do a full installation; if
that fails, a personal installation; if that fails, a minimal
installation.

    $ (wget -O - pi.dk/3 || lynx -source pi.dk/3 || curl pi.dk/3/ || \
       fetch -o - http://pi.dk/3 ) > install.sh
    $ sha1sum install.sh | grep 883c667e01eed62f975ad28b6d50e22a
    12345678 883c667e 01eed62f 975ad28b 6d50e22a
    $ md5sum install.sh | grep cc21b4c943fd03e93ae1ae49e28573c0
    cc21b4c9 43fd03e9 3ae1ae49 e28573c0
    $ sha512sum install.sh | grep da012ec113b49a54e705f86d51e784ebced224fdf
    79945d9d 250b42a4 2067bb00 99da012e c113b49a 54e705f8 6d51e784 ebced224
    fdff3f52 ca588d64 e75f6033 61bd543f d631f592 2f87ceb2 ab034149 6df84a35
    $ bash install.sh

This will literally install faster than reading the rest of this
document.


= Full installation =

Full installation of GNU Parallel is as simple as:

    wget https://ftpmirror.gnu.org/parallel/parallel-20231122.tar.bz2
    wget https://ftpmirror.gnu.org/parallel/parallel-20231122.tar.bz2.sig
    gpg parallel-20231122.tar.bz2.sig
    bzip2 -dc parallel-20231122.tar.bz2 | tar xvf -
    cd parallel-20231122
    ./configure && make && sudo make install


= Personal installation =

If you are not root you can add ~/bin to your path and install in
~/bin and ~/share:

    wget https://ftpmirror.gnu.org/parallel/parallel-20231122.tar.bz2
    wget https://ftpmirror.gnu.org/parallel/parallel-20231122.tar.bz2.sig
    gpg parallel-20231122.tar.bz2.sig
    bzip2 -dc parallel-20231122.tar.bz2 | tar xvf -
    cd parallel-20231122
    ./configure --prefix=$HOME && make && make install

Or if your system lacks 'make' you can simply copy src/parallel
src/sem src/niceload src/sql to a dir in your path.


= Minimal installation =

If you just need parallel and do not have 'make' installed (maybe the
system is old or Microsoft Windows):

    wget https://git.savannah.gnu.org/cgit/parallel.git/plain/src/parallel
    chmod 755 parallel
    cp parallel sem
    mv parallel sem dir-in-your-$PATH/bin/


= Installation on compute servers =

If you are developing your script to run on a remote server, that does
not have GNU Parallel installed, but you have it installed on you
development machine, then you can use `parallel --embed`.

    parallel --embed > newscript.sh

Just edit the last lines of newscript.sh and copy it to the compute
server.


= Test the installation =

After this you should be able to do:

    parallel -j0 ping -nc 3 ::: qubes-os.org gnu.org freenetproject.org

This will send 3 ping packets to 3 different hosts in parallel and print
the output when they complete.

Watch the intro video for a quick introduction:
https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1

Walk through the tutorial (man parallel_tutorial). You command line
will love you for it.

When using programs that use GNU Parallel to process data for
publication please cite:

    Tange, O. (2023, November 22). GNU Parallel 20231122 ('Grindavík').
    Zenodo. https://doi.org/10.5281/zenodo.10199085

Copyright (C) 2007-2022 Ole Tange, http://ole.tange.dk and Free
Software Foundation, Inc.


= New versions =

New versions will be released at: https://ftp.gnu.org/gnu/parallel/


= Dependencies =

GNU Parallel should work with a normal full Perl installation. However,
if you system has split up Perl into multiple packages then these are
the important ones:

    opkg install perlbase-getopt perlbase-ipc procps-ng-ps perlbase-mime

SPDX-FileCopyrightText: 2021-2022 Ole Tange, http://ole.tange.dk and Free Software and Foundation, Inc.
SPDX-License-Identifier: GPL-3.0-or-later
