path: root/src/env_parallel.pod

#!/usr/bin/perl -w

# SPDX-FileCopyrightText: 2021-2022 Ole Tange, http://ole.tange.dk and Free Software and Foundation, Inc.
# SPDX-License-Identifier: GFDL-1.3-or-later
# SPDX-License-Identifier: CC-BY-SA-4.0

=encoding utf8

=head1 NAME

env_parallel - export environment to GNU parallel


=head1 SYNOPSIS

B<env_parallel> [--record-env|--session|--end-session]
  [options for GNU Parallel]


=head1 DESCRIPTION

B<env_parallel> is a shell function that exports the current
environment to GNU B<parallel>.

If the shell function is not loaded, a dummy script will be run
instead that explains how to install the function.

B<env_parallel> is 100 ms slower at startup than pure GNU
B<parallel>, and takes up to 30% longer to start a job (typically 15 ms).

Due to the problem with environment space (see below) the recommended
usage is either:

  # Do --record-env into $PARALLEL_IGNORED_NAMES
  env_parallel --session

  # Define whatever you want to use
  myfunc() { myalias and functions $myvar work. $1.; }
  alias myalias='echo Aliases'
  myvar='and variables'

  # env_parallel will not export names in $PARALLEL_IGNORED_NAMES
  env_parallel -S localhost myfunc ::: Hooray

Or:

  # Record the "clean" environment (this only needs to be run once)
  env_parallel --record-env

  # Optionally edit ~/.parallel/ignored_vars (only needed once)

  # Define whatever you want to use
  myfunc() { myalias and functions $myvar work. $1.; }
  alias myalias='echo Aliases'
  myvar='and variables'

  # Use --env _ to only transfer the names not in the "empty" environment
  env_parallel --env _ -S localhost myfunc ::: Hooray

In B<csh> B<--session> is not supported:

  # Record the "clean" environment - this only needs to be run once
  env_parallel --record-env

  # Optionally edit ~/.parallel/ignored_vars - only needed once

  # Define whatever you want to use
  alias myalias 'echo Aliases $myvar \!*.'
  set myvar='and variables'

  # Use --env _ to only transfer the names not in the "empty" environment
  env_parallel --env _ -S localhost myalias ::: work

=head2 Environment space

By default B<env_parallel> will export all environment variables,
arrays, aliases, functions and shell options (see details for the
individual shells below).

But this only works if the size of the current environment is smaller
than the maximal length of a command and smaller than half of the max
if running remotely. E.g. The max size of Bash's command is 128 KB, so
B<env_parallel> will fail if 'B<set | wc -c>' is bigger than 128
KB. Technically the limit is in execve(1) which IPC::open3 uses.

Bash completion functions are well-known for taking up well over 128
KB of environment space and the primary reason for causing
B<env_parallel> to fail.

Instead you can use B<--env> to specify which variables, arrays,
aliases and functions to export as this will only export those with
the given name. Or follow the recommended usage in shown in
DESCRIPTION.


=head1 OPTIONS

Same as GNU B<parallel> in addition to these:

=over 4

=item B<--end-session>

Undo last B<--session>


=item B<--record-env>

Record all names currently defined to be ignored every time running
B<env_parallel> in the future.


=item B<--session>

Ignore all names currently defined. Aliases, variables, arrays, and
functions currently defined will not be transferred.

But names defined I<after> running B<parallel --session> I<will> be
transferred.

This is only valid in the running shell, and can be undone with
B<parallel --end-session>.

You can run multiple B<--session> inside each other:

  env_parallel --session
  var=not
  # var is transferred
  env_parallel -Slocalhost 'echo var is $var' ::: ignored
  env_parallel --session
  # var is not transferred
  env_parallel -Slocalhost 'echo var is $var' ::: ignored
  env_parallel --end-session
  # var is transferred again
  env_parallel -Slocalhost 'echo var is $var' ::: ignored



=back


=head1 SUPPORTED SHELLS

=head2 Ash

=head3 Installation

Put this in $HOME/.profile:

  . `which env_parallel.ash`

E.g. by doing:

  echo '. `which env_parallel.ash`' >> $HOME/.profile

=head3 Supported use

B<--env> is supported to export only the variable, or alias with the
given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel multiline ::: work
  env_parallel -S server multiline ::: work
  env_parallel --env multiline multiline ::: work
  env_parallel --env multiline -S server multiline ::: work

=item functions

  ash cannot list defined functions - thus is not supported.

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

Arrays are not supported by Ash.

=back

=head2 Bash

=head3 Installation

Put this in $HOME/.bashrc:

  . `which env_parallel.bash`

E.g. by doing:

  echo '. `which env_parallel.bash`' >> $HOME/.bashrc

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel 'multiline {};
    echo but only when followed by a newline' ::: work
  env_parallel -S server 'multiline {};
    echo but only when followed by a newline' ::: work
  env_parallel --env multiline 'multiline {};
    echo but only when followed by a newline' ::: work
  env_parallel --env multiline -S server 'multiline {};
    echo but only when followed by a newline' ::: work

=item functions

  myfunc() { echo functions $*; }
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  myarray=(arrays work, too)
  env_parallel -k echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k -S server echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray -S server \
    echo '${myarray[{}]}' ::: 0 1 2

=back

=head3 BUGS

Due to a bug in Bash, aliases containing newlines must be followed by
a newline in the command. Some systems are not affected by this bug,
but will print a warning anyway.

=head2 csh

B<env_parallel> for B<csh> breaks B<$PARALLEL>, so do not use
B<$PARALLEL>.

=head3 Installation

Put this in $HOME/.cshrc:

  source `which env_parallel.csh`

E.g. by doing:

  echo 'source `which env_parallel.csh`' >> $HOME/.cshrc

=head3 Supported use

B<--env> is supported to export only the variable, alias, or
array with the given name. Multiple B<--env>s can be given.

=over 8

=item aliases

  alias myecho 'echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

=item functions

Not supported by B<csh>.

=item variables

  set myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays with no special chars

  set myarray=(arrays work, too)
  env_parallel -k echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k -S server echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray -S server \
    echo \$'{myarray[{}]}' ::: 1 2 3

=back


=head2 Dash

=head3 Installation

Put this in $HOME/.profile:

  . `which env_parallel.dash`

E.g. by doing:

  echo '. `which env_parallel.dash`' >> $HOME/.profile

=head3 Supported use

B<--env> is supported to export only the variable, or alias with the
given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel multiline ::: work
  env_parallel -S server multiline ::: work
  env_parallel --env multiline multiline ::: work
  env_parallel --env multiline -S server multiline ::: work

=item functions

  dash cannot list defined functions - thus is not supported.

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  dash does not support arrays.

=back


=head2 fish

=head3 Installation

Put this in $HOME/.config/fish/config.fish:

  source (which env_parallel.fish)

E.g. by doing:

  echo 'source (which env_parallel.fish)' \
    >> $HOME/.config/fish/config.fish

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho 'echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

=item functions

  function myfunc
    echo functions $argv
  end
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  set myvar variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  set myarray arrays work, too
  env_parallel -k echo '$myarray[{}]' ::: 1 2 3
  env_parallel -k -S server echo '$myarray[{}]' ::: 1 2 3
  env_parallel -k --env myarray echo '$myarray[{}]' ::: 1 2 3
  env_parallel -k --env myarray -S server \
    echo '$myarray[{}]' ::: 1 2 3

=back


=head2 ksh

=head3 Installation

Put this in $HOME/.kshrc:

  source `which env_parallel.ksh`

E.g. by doing:

  echo 'source `which env_parallel.ksh`' >> $HOME/.kshrc

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel multiline ::: work
  env_parallel -S server multiline ::: work
  env_parallel --env multiline multiline ::: work
  env_parallel --env multiline -S server multiline ::: work

=item functions

  myfunc() { echo functions $*; }
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  myarray=(arrays work, too)
  env_parallel -k echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k -S server echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray -S server \
    echo '${myarray[{}]}' ::: 0 1 2

=back


=head2 mksh

=head3 Installation

Put this in $HOME/.mkshrc:

  source `which env_parallel.mksh`

E.g. by doing:

  echo 'source `which env_parallel.mksh`' >> $HOME/.mkshrc

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel multiline ::: work
  env_parallel -S server multiline ::: work
  env_parallel --env multiline multiline ::: work
  env_parallel --env multiline -S server multiline ::: work

=item functions

  myfunc() { echo functions $*; }
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  myarray=(arrays work, too)
  env_parallel -k echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k -S server echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray echo '${myarray[{}]}' ::: 0 1 2
  env_parallel -k --env myarray -S server \
    echo '${myarray[{}]}' ::: 0 1 2

=back


=head2 pdksh

=head3 Installation

Put this in $HOME/.profile:

  source `which env_parallel.pdksh`

E.g. by doing:

  echo 'source `which env_parallel.pdksh`' >> $HOME/.profile

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho="echo aliases";
  env_parallel myecho ::: work;
  env_parallel -S server myecho ::: work;
  env_parallel --env myecho myecho ::: work;
  env_parallel --env myecho -S server myecho ::: work

=item functions

  myfunc() { echo functions $*; };
  env_parallel myfunc ::: work;
  env_parallel -S server myfunc ::: work;
  env_parallel --env myfunc myfunc ::: work;
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables;
  env_parallel echo "\$myvar" ::: work;
  env_parallel -S server echo "\$myvar" ::: work;
  env_parallel --env myvar echo "\$myvar" ::: work;
  env_parallel --env myvar -S server echo "\$myvar" ::: work

=item arrays

  myarray=(arrays work, too);
  env_parallel -k echo "\${myarray[{}]}" ::: 0 1 2;
  env_parallel -k -S server echo "\${myarray[{}]}" ::: 0 1 2;
  env_parallel -k --env myarray echo "\${myarray[{}]}" ::: 0 1 2;
  env_parallel -k --env myarray -S server \
    echo "\${myarray[{}]}" ::: 0 1 2

=back


=head2 sh

=head3 Installation

Put this in $HOME/.profile:

  . `which env_parallel.sh`

E.g. by doing:

  echo '. `which env_parallel.sh`' >> $HOME/.profile

=head3 Supported use

B<--env> is supported to export only the variable, or alias with the
given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  sh does not support aliases.

=item functions

  myfunc() { echo functions $*; }
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  sh does not support arrays.

=back


=head2 tcsh

B<env_parallel> for B<tcsh> breaks B<$PARALLEL>, so do not use
B<$PARALLEL>.

=head3 Installation

Put this in $HOME/.tcshrc:

  source `which env_parallel.tcsh`

E.g. by doing:

  echo 'source `which env_parallel.tcsh`' >> $HOME/.tcshrc

=head3 Supported use

B<--env> is supported to export only the variable, alias, or
array with the given name. Multiple B<--env>s can be given.

=over 8

=item aliases

  alias myecho 'echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

=item functions

Not supported by B<tcsh>.

=item variables

  set myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays with no special chars

  set myarray=(arrays work, too)
  env_parallel -k echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k -S server echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray echo \$'{myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray -S server \
    echo \$'{myarray[{}]}' ::: 1 2 3

=back


=head2 Zsh

=head3 Installation

Put this in $HOME/.zshrc:

  . `which env_parallel.zsh`

E.g. by doing:

  echo '. `which env_parallel.zsh`' >> $HOME/.zshenv

=head3 Supported use

B<--env> is supported to export only the variable, alias, function, or
array with the given name. Multiple B<--env>s can be given.

B<--session> is supported.

=over 8

=item aliases

  alias myecho='echo aliases'
  env_parallel myecho ::: work
  env_parallel -S server myecho ::: work
  env_parallel --env myecho myecho ::: work
  env_parallel --env myecho -S server myecho ::: work

  alias multiline='echo multiline
    echo aliases'
  env_parallel multiline ::: work
  env_parallel -S server multiline ::: work
  env_parallel --env multiline multiline ::: work
  env_parallel --env multiline -S server multiline ::: work

=item functions

  myfunc() { echo functions $*; }
  env_parallel myfunc ::: work
  env_parallel -S server myfunc ::: work
  env_parallel --env myfunc myfunc ::: work
  env_parallel --env myfunc -S server myfunc ::: work

=item variables

  myvar=variables
  env_parallel echo '$myvar' ::: work
  env_parallel -S server echo '$myvar' ::: work
  env_parallel --env myvar echo '$myvar' ::: work
  env_parallel --env myvar -S server echo '$myvar' ::: work

=item arrays

  myarray=(arrays work, too)
  env_parallel -k echo '${myarray[{}]}' ::: 1 2 3
  env_parallel -k -S server echo '${myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray echo '${myarray[{}]}' ::: 1 2 3
  env_parallel -k --env myarray -S server \
    echo '${myarray[{}]}' ::: 1 2 3

=back


=head1 EXIT STATUS

Same as GNU B<parallel>.


=head1 AUTHOR

When using GNU B<env_parallel> for a publication please cite:

O. Tange (2018): GNU Parallel 2018, March 2018, ISBN 9781387509881,
DOI: 10.5281/zenodo.1146014.

This helps funding further development; and it won't cost you a cent.
If you pay 10000 EUR you should feel free to use GNU Parallel without citing.

Copyright (C) 2007-10-18 Ole Tange, http://ole.tange.dk

Copyright (C) 2008-2010 Ole Tange, http://ole.tange.dk

Copyright (C) 2010-2022 Ole Tange, http://ole.tange.dk and Free
Software Foundation, Inc.


=head1 LICENSE

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/>.

=head2 Documentation license I

Permission is granted to copy, distribute and/or modify this
documentation under the terms of the GNU Free Documentation License,
Version 1.3 or any later version published by the Free Software
Foundation; with no Invariant Sections, with no Front-Cover Texts, and
with no Back-Cover Texts.  A copy of the license is included in the
file LICENSES/GFDL-1.3-or-later.txt.


=head2 Documentation license II

You are free:

=over 9

=item B<to Share>

to copy, distribute and transmit the work

=item B<to Remix>

to adapt the work

=back

Under the following conditions:

=over 9

=item B<Attribution>

You must attribute the work in the manner specified by the author or
licensor (but not in any way that suggests that they endorse you or
your use of the work).

=item B<Share Alike>

If you alter, transform, or build upon this work, you may distribute
the resulting work only under the same, similar or a compatible
license.

=back

With the understanding that:

=over 9

=item B<Waiver>

Any of the above conditions can be waived if you get permission from
the copyright holder.

=item B<Public Domain>

Where the work or any of its elements is in the public domain under
applicable law, that status is in no way affected by the license.

=item B<Other Rights>

In no way are any of the following rights affected by the license:

=over 2

=item *

Your fair dealing or fair use rights, or other applicable
copyright exceptions and limitations;

=item *

The author's moral rights;

=item *

Rights other persons may have either in the work itself or in
how the work is used, such as publicity or privacy rights.

=back

=back

=over 9

=item B<Notice>

For any reuse or distribution, you must make clear to others the
license terms of this work.

=back

A copy of the full license is included in the file as
LICENCES/CC-BY-SA-4.0.txt


=head1 DEPENDENCIES

B<env_parallel> uses GNU B<parallel>.


=head1 SEE ALSO

B<parallel>(1), B<ash>(1), B<bash>(1), B<csh>(1), B<dash>(1),
B<fish>(1), B<ksh>(1), B<pdksh>(1) B<tcsh>(1), B<zsh>(1).


=cut