\input texinfo
@setfilename GNU_Parallel_Tutorial.info
@documentencoding utf-8
@settitle GNU Parallel Tutorial
@node Top
@top GNU Parallel Tutorial
@menu
* GNU Parallel Tutorial::
* Prerequisites::
* Input sources::
* Building the command line::
* Controlling the output::
* Controlling the execution::
* Remote execution::
* Saving output to shell variables (advanced)::
* Saving to an SQL base (advanced)::
* --pipe::
* Shebang::
* Semaphore::
* Informational::
* Profiles::
* Spread the word::
@end menu
@node GNU Parallel Tutorial
@chapter GNU Parallel Tutorial
This tutorial shows off much of GNU @strong{parallel}'s functionality. The
tutorial is meant to learn the options in and syntax of GNU
@strong{parallel}. The tutorial is @strong{not} to show realistic examples from the
real world.
@menu
* Reader's guide::
@end menu
@node Reader's guide
@section Reader's guide
If you prefer reading a book buy @strong{GNU Parallel 2018} at
https://www.lulu.com/shop/ole-tange/gnu-parallel-2018/paperback/product-23558902.html
or download it at: https://doi.org/10.5281/zenodo.1146014
Otherwise start by watching the intro videos for a quick introduction:
https://www.youtube.com/playlist?list=PL284C9FF2488BC6D1
Then browse through the examples (@strong{man parallel_examples}). That will give
you an idea of what GNU @strong{parallel} is capable of.
If you want to dive even deeper: spend a couple of hours walking
through the tutorial (@strong{man parallel_tutorial}). Your command line
will love you for it.
Finally you may want to look at the rest of the manual (@strong{man
parallel}) if you have special needs not already covered.
If you want to know the design decisions behind GNU @strong{parallel}, try:
@strong{man parallel_design}. This is also a good intro if you intend to
change GNU @strong{parallel}.
@node Prerequisites
@chapter Prerequisites
To run this tutorial you must have the following:
@table @asis
@item parallel >= version 20160822
@anchor{parallel >= version 20160822}
Install the newest version using your package manager (recommended for
security reasons), the way described in README, or with this command:
@verbatim
$ (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
12345678 51621b7f 1ee103c0 0783aae4 ef9889f8
$ md5sum install.sh
62eada78 703b5500 241b8e50 baf62758
$ sha512sum install.sh
160d3159 9480cf5c a101512f 150b7ac0 206a65dc 86f2bb6b bdf1a2bc 96bc6d06
7f8237c2 0964b67f bccf8a93 332528fa 11e5ab43 2a6226a6 ceb197ab 7f03c061
$ bash install.sh
@end verbatim
This will also install the newest version of the tutorial which you
can see by running this:
@verbatim
man parallel_tutorial
@end verbatim
Most of the tutorial will work on older versions, too.
@item abc-file:
@anchor{abc-file:}
The file can be generated by this command:
@verbatim
parallel -k echo ::: A B C > abc-file
@end verbatim
@item def-file:
@anchor{def-file:}
The file can be generated by this command:
@verbatim
parallel -k echo ::: D E F > def-file
@end verbatim
@item abc0-file:
@anchor{abc0-file:}
The file can be generated by this command:
@verbatim
perl -e 'printf "A\0B\0C\0"' > abc0-file
@end verbatim
@item abc_-file:
@anchor{abc_-file:}
The file can be generated by this command:
@verbatim
perl -e 'printf "A_B_C_"' > abc_-file
@end verbatim
@item tsv-file.tsv
@anchor{tsv-file.tsv}
The file can be generated by this command:
@verbatim
perl -e 'printf "f1\tf2\nA\tB\nC\tD\n"' > tsv-file.tsv
@end verbatim
@item num8
@anchor{num8}
The file can be generated by this command:
@verbatim
perl -e 'for(1..8){print "$_\n"}' > num8
@end verbatim
@item num128
@anchor{num128}
The file can be generated by this command:
@verbatim
perl -e 'for(1..128){print "$_\n"}' > num128
@end verbatim
@item num30000
@anchor{num30000}
The file can be generated by this command:
@verbatim
perl -e 'for(1..30000){print "$_\n"}' > num30000
@end verbatim
@item num1000000
@anchor{num1000000}
The file can be generated by this command:
@verbatim
perl -e 'for(1..1000000){print "$_\n"}' > num1000000
@end verbatim
@item num_%header
@anchor{num_%header}
The file can be generated by this command:
@verbatim
(echo %head1; echo %head2; \
perl -e 'for(1..10){print "$_\n"}') > num_%header
@end verbatim
@item fixedlen
@anchor{fixedlen}
The file can be generated by this command:
@verbatim
perl -e 'print "HHHHAAABBBCCC"' > fixedlen
@end verbatim
@item For remote running: ssh login on 2 servers with no password in $SERVER1 and $SERVER2 must work.
@anchor{For remote running: ssh login on 2 servers with no password in $SERVER1 and $SERVER2 must work.}
@verbatim
SERVER1=server.example.com
SERVER2=server2.example.net
@end verbatim
So you must be able to do this without entering a password:
@verbatim
ssh $SERVER1 echo works
ssh $SERVER2 echo works
@end verbatim
It can be setup by running @strong{ssh-keygen -t dsa; ssh-copy-id $SERVER1}
and using an empty passphrase, or you can use @strong{ssh-agent}.
@end table
@node Input sources
@chapter Input sources
GNU @strong{parallel} reads input from input sources. These can be files, the
command line, and stdin (standard input or a pipe).
@menu
* A single input source::
* Multiple input sources::
* Changing the argument separator.::
* Changing the argument delimiter::
* End-of-file value for input source::
* Skipping empty lines::
@end menu
@node A single input source
@section A single input source
Input can be read from the command line:
@verbatim
parallel echo ::: A B C
@end verbatim
Output (the order may be different because the jobs are run in
parallel):
@verbatim
A
B
C
@end verbatim
The input source can be a file:
@verbatim
parallel -a abc-file echo
@end verbatim
Output: Same as above.
STDIN (standard input) can be the input source:
@verbatim
cat abc-file | parallel echo
@end verbatim
Output: Same as above.
@node Multiple input sources
@section Multiple input sources
GNU @strong{parallel} can take multiple input sources given on the command
line. GNU @strong{parallel} then generates all combinations of the input
sources:
@verbatim
parallel echo ::: A B C ::: D E F
@end verbatim
Output (the order may be different):
@verbatim
A D
A E
A F
B D
B E
B F
C D
C E
C F
@end verbatim
The input sources can be files:
@verbatim
parallel -a abc-file -a def-file echo
@end verbatim
Output: Same as above.
STDIN (standard input) can be one of the input sources using @strong{-}:
@verbatim
cat abc-file | parallel -a - -a def-file echo
@end verbatim
Output: Same as above.
Instead of @strong{-a} files can be given after @strong{::::}:
@verbatim
cat abc-file | parallel echo :::: - def-file
@end verbatim
Output: Same as above.
::: and :::: can be mixed:
@verbatim
parallel echo ::: A B C :::: def-file
@end verbatim
Output: Same as above.
@menu
* Linking arguments from input sources::
@end menu
@node Linking arguments from input sources
@subsection Linking arguments from input sources
With @strong{--link} you can link the input sources and get one argument
from each input source:
@verbatim
parallel --link echo ::: A B C ::: D E F
@end verbatim
Output (the order may be different):
@verbatim
A D
B E
C F
@end verbatim
If one of the input sources is too short, its values will wrap:
@verbatim
parallel --link echo ::: A B C D E ::: F G
@end verbatim
Output (the order may be different):
@verbatim
A F
B G
C F
D G
E F
@end verbatim
For more flexible linking you can use @strong{:::+} and @strong{::::+}. They work
like @strong{:::} and @strong{::::} except they link the previous input source to
this input source.
This will link ABC to GHI:
@verbatim
parallel echo :::: abc-file :::+ G H I :::: def-file
@end verbatim
Output (the order may be different):
@verbatim
A G D
A G E
A G F
B H D
B H E
B H F
C I D
C I E
C I F
@end verbatim
This will link GHI to DEF:
@verbatim
parallel echo :::: abc-file ::: G H I ::::+ def-file
@end verbatim
Output (the order may be different):
@verbatim
A G D
A H E
A I F
B G D
B H E
B I F
C G D
C H E
C I F
@end verbatim
If one of the input sources is too short when using @strong{:::+} or
@strong{::::+}, the rest will be ignored:
@verbatim
parallel echo ::: A B C D E :::+ F G
@end verbatim
Output (the order may be different):
@verbatim
A F
B G
@end verbatim
@node Changing the argument separator.
@section Changing the argument separator.
GNU @strong{parallel} can use other separators than @strong{:::} or @strong{::::}. This is
typically useful if @strong{:::} or @strong{::::} is used in the command to run:
@verbatim
parallel --arg-sep ,, echo ,, A B C :::: def-file
@end verbatim
Output (the order may be different):
@verbatim
A D
A E
A F
B D
B E
B F
C D
C E
C F
@end verbatim
Changing the argument file separator:
@verbatim
parallel --arg-file-sep // echo ::: A B C // def-file
@end verbatim
Output: Same as above.
@node Changing the argument delimiter
@section Changing the argument delimiter
GNU @strong{parallel} will normally treat a full line as a single argument: It
uses @strong{\n} as argument delimiter. This can be changed with @strong{-d}:
@verbatim
parallel -d _ echo :::: abc_-file
@end verbatim
Output (the order may be different):
@verbatim
A
B
C
@end verbatim
NUL can be given as @strong{\0}:
@verbatim
parallel -d '\0' echo :::: abc0-file
@end verbatim
Output: Same as above.
A shorthand for @strong{-d '\0'} is @strong{-0} (this will often be used to read files
from @strong{find ... -print0}):
@verbatim
parallel -0 echo :::: abc0-file
@end verbatim
Output: Same as above.
@node End-of-file value for input source
@section End-of-file value for input source
GNU @strong{parallel} can stop reading when it encounters a certain value:
@verbatim
parallel -E stop echo ::: A B stop C D
@end verbatim
Output:
@verbatim
A
B
@end verbatim
@node Skipping empty lines
@section Skipping empty lines
Using @strong{--no-run-if-empty} GNU @strong{parallel} will skip empty lines.
@verbatim
(echo 1; echo; echo 2) | parallel --no-run-if-empty echo
@end verbatim
Output:
@verbatim
1
2
@end verbatim
@node Building the command line
@chapter Building the command line
@menu
* No command means arguments are commands::
* Replacement strings::
* More than one argument::
* Quoting::
* Trimming space::
* Respecting the shell::
@end menu
@node No command means arguments are commands
@section No command means arguments are commands
If no command is given after parallel the arguments themselves are
treated as commands:
@verbatim
parallel ::: ls 'echo foo' pwd
@end verbatim
Output (the order may be different):
@verbatim
[list of files in current dir]
foo
[/path/to/current/working/dir]
@end verbatim
The command can be a script, a binary or a Bash function if the function is
exported using @strong{export -f}:
@verbatim
# Only works in Bash
my_func() {
echo in my_func $1
}
export -f my_func
parallel my_func ::: 1 2 3
@end verbatim
Output (the order may be different):
@verbatim
in my_func 1
in my_func 2
in my_func 3
@end verbatim
@node Replacement strings
@section Replacement strings
@menu
* The 7 predefined replacement strings::
* Changing the replacement strings::
* Perl expression replacement string::
* Positional replacement strings::
* Positional perl expression replacement string::
* Input from columns::
* Header defined replacement strings::
* More pre-defined replacement strings with --plus::
* Dynamic replacement strings with --plus::
@end menu
@node The 7 predefined replacement strings
@subsection The 7 predefined replacement strings
GNU @strong{parallel} has several replacement strings. If no replacement
strings are used the default is to append @strong{@{@}}:
@verbatim
parallel echo ::: A/B.C
@end verbatim
Output:
@verbatim
A/B.C
@end verbatim
The default replacement string is @strong{@{@}}:
@verbatim
parallel echo {} ::: A/B.C
@end verbatim
Output:
@verbatim
A/B.C
@end verbatim
The replacement string @strong{@{.@}} removes the extension:
@verbatim
parallel echo {.} ::: A/B.C
@end verbatim
Output:
@verbatim
A/B
@end verbatim
The replacement string @strong{@{/@}} removes the path:
@verbatim
parallel echo {/} ::: A/B.C
@end verbatim
Output:
@verbatim
B.C
@end verbatim
The replacement string @strong{@{//@}} keeps only the path:
@verbatim
parallel echo {//} ::: A/B.C
@end verbatim
Output:
@verbatim
A
@end verbatim
The replacement string @strong{@{/.@}} removes the path and the extension:
@verbatim
parallel echo {/.} ::: A/B.C
@end verbatim
Output:
@verbatim
B
@end verbatim
The replacement string @strong{@{#@}} gives the job number:
@verbatim
parallel echo {#} ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
1
2
3
@end verbatim
The replacement string @strong{@{%@}} gives the job slot number (between 1 and
number of jobs to run in parallel):
@verbatim
parallel -j 2 echo {%} ::: A B C
@end verbatim
Output (the order may be different and 1 and 2 may be swapped):
@verbatim
1
2
1
@end verbatim
@node Changing the replacement strings
@subsection Changing the replacement strings
The replacement string @strong{@{@}} can be changed with @strong{-I}:
@verbatim
parallel -I ,, echo ,, ::: A/B.C
@end verbatim
Output:
@verbatim
A/B.C
@end verbatim
The replacement string @strong{@{.@}} can be changed with @strong{--extensionreplace}:
@verbatim
parallel --extensionreplace ,, echo ,, ::: A/B.C
@end verbatim
Output:
@verbatim
A/B
@end verbatim
The replacement string @strong{@{/@}} can be replaced with @strong{--basenamereplace}:
@verbatim
parallel --basenamereplace ,, echo ,, ::: A/B.C
@end verbatim
Output:
@verbatim
B.C
@end verbatim
The replacement string @strong{@{//@}} can be changed with @strong{--dirnamereplace}:
@verbatim
parallel --dirnamereplace ,, echo ,, ::: A/B.C
@end verbatim
Output:
@verbatim
A
@end verbatim
The replacement string @strong{@{/.@}} can be changed with @strong{--basenameextensionreplace}:
@verbatim
parallel --basenameextensionreplace ,, echo ,, ::: A/B.C
@end verbatim
Output:
@verbatim
B
@end verbatim
The replacement string @strong{@{#@}} can be changed with @strong{--seqreplace}:
@verbatim
parallel --seqreplace ,, echo ,, ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
1
2
3
@end verbatim
The replacement string @strong{@{%@}} can be changed with @strong{--slotreplace}:
@verbatim
parallel -j2 --slotreplace ,, echo ,, ::: A B C
@end verbatim
Output (the order may be different and 1 and 2 may be swapped):
@verbatim
1
2
1
@end verbatim
@node Perl expression replacement string
@subsection Perl expression replacement string
When predefined replacement strings are not flexible enough a perl
expression can be used instead. One example is to remove two
extensions: foo.tar.gz becomes foo
@verbatim
parallel echo '{= s:\.[^.]+$::;s:\.[^.]+$::; =}' ::: foo.tar.gz
@end verbatim
Output:
@verbatim
foo
@end verbatim
In @strong{@{= =@}} you can access all of GNU @strong{parallel}'s internal functions
and variables. A few are worth mentioning.
@strong{total_jobs()} returns the total number of jobs:
@verbatim
parallel echo Job {#} of {= '$_=total_jobs()' =} ::: {1..5}
@end verbatim
Output:
@verbatim
Job 1 of 5
Job 2 of 5
Job 3 of 5
Job 4 of 5
Job 5 of 5
@end verbatim
@strong{Q(...)} shell quotes the string:
@verbatim
parallel echo {} shell quoted is {= '$_=Q($_)' =} ::: '*/!#$'
@end verbatim
Output:
@verbatim
*/!#$ shell quoted is \*/\!\#\$
@end verbatim
@strong{skip()} skips the job:
@verbatim
parallel echo {= 'if($_==3) { skip() }' =} ::: {1..5}
@end verbatim
Output:
@verbatim
1
2
4
5
@end verbatim
@strong{@@arg} contains the input source variables:
@verbatim
parallel echo {= 'if($arg[1]==$arg[2]) { skip() }' =} \
::: {1..3} ::: {1..3}
@end verbatim
Output:
@verbatim
1 2
1 3
2 1
2 3
3 1
3 2
@end verbatim
If the strings @strong{@{=} and @strong{=@}} cause problems they can be replaced with @strong{--parens}:
@verbatim
parallel --parens ,,,, echo ',, s:\.[^.]+$::;s:\.[^.]+$::; ,,' \
::: foo.tar.gz
@end verbatim
Output:
@verbatim
foo
@end verbatim
To define a shorthand replacement string use @strong{--rpl}:
@verbatim
parallel --rpl '.. s:\.[^.]+$::;s:\.[^.]+$::;' echo '..' \
::: foo.tar.gz
@end verbatim
Output: Same as above.
If the shorthand starts with @strong{@{} it can be used as a positional
replacement string, too:
@verbatim
parallel --rpl '{..} s:\.[^.]+$::;s:\.[^.]+$::;' echo '{..}'
::: foo.tar.gz
@end verbatim
Output: Same as above.
If the shorthand contains matching parenthesis the replacement string
becomes a dynamic replacement string and the string in the parenthesis
can be accessed as $$1. If there are multiple matching parenthesis,
the matched strings can be accessed using $$2, $$3 and so on.
You can think of this as giving arguments to the replacement
string. Here we give the argument @strong{.tar.gz} to the replacement string
@strong{@{%@emph{string}@}} which removes @emph{string}:
@verbatim
parallel --rpl '{%(.+?)} s/$$1$//;' echo {%.tar.gz}.zip ::: foo.tar.gz
@end verbatim
Output:
@verbatim
foo.zip
@end verbatim
Here we give the two arguments @strong{tar.gz} and @strong{zip} to the replacement
string @strong{@{/@emph{string1}/@emph{string2}@}} which replaces @emph{string1} with
@emph{string2}:
@verbatim
parallel --rpl '{/(.+?)/(.*?)} s/$$1/$$2/;' echo {/tar.gz/zip} \
::: foo.tar.gz
@end verbatim
Output:
@verbatim
foo.zip
@end verbatim
GNU @strong{parallel}'s 7 replacement strings are implemented as this:
@verbatim
--rpl '{} '
--rpl '{#} $_=$job->seq()'
--rpl '{%} $_=$job->slot()'
--rpl '{/} s:.*/::'
--rpl '{//} $Global::use{"File::Basename"} ||=
eval "use File::Basename; 1;"; $_ = dirname($_);'
--rpl '{/.} s:.*/::; s:\.[^/.]+$::;'
--rpl '{.} s:\.[^/.]+$::'
@end verbatim
@node Positional replacement strings
@subsection Positional replacement strings
With multiple input sources the argument from the individual input
sources can be accessed with @w{@strong{@{}number@strong{@}}}:
@verbatim
parallel echo {1} and {2} ::: A B ::: C D
@end verbatim
Output (the order may be different):
@verbatim
A and C
A and D
B and C
B and D
@end verbatim
The positional replacement strings can also be modified using @strong{/}, @strong{//}, @strong{/.}, and @strong{.}:
@verbatim
parallel echo /={1/} //={1//} /.={1/.} .={1.} ::: A/B.C D/E.F
@end verbatim
Output (the order may be different):
@verbatim
/=B.C //=A /.=B .=A/B
/=E.F //=D /.=E .=D/E
@end verbatim
If a position is negative, it will refer to the input source counted
from behind:
@verbatim
parallel echo 1={1} 2={2} 3={3} -1={-1} -2={-2} -3={-3} \
::: A B ::: C D ::: E F
@end verbatim
Output (the order may be different):
@verbatim
1=A 2=C 3=E -1=E -2=C -3=A
1=A 2=C 3=F -1=F -2=C -3=A
1=A 2=D 3=E -1=E -2=D -3=A
1=A 2=D 3=F -1=F -2=D -3=A
1=B 2=C 3=E -1=E -2=C -3=B
1=B 2=C 3=F -1=F -2=C -3=B
1=B 2=D 3=E -1=E -2=D -3=B
1=B 2=D 3=F -1=F -2=D -3=B
@end verbatim
@node Positional perl expression replacement string
@subsection Positional perl expression replacement string
To use a perl expression as a positional replacement string simply
prepend the perl expression with number and space:
@verbatim
parallel echo '{=2 s:\.[^.]+$::;s:\.[^.]+$::; =} {1}' \
::: bar ::: foo.tar.gz
@end verbatim
Output:
@verbatim
foo bar
@end verbatim
If a shorthand defined using @strong{--rpl} starts with @strong{@{} it can be used as
a positional replacement string, too:
@verbatim
parallel --rpl '{..} s:\.[^.]+$::;s:\.[^.]+$::;' echo '{2..} {1}' \
::: bar ::: foo.tar.gz
@end verbatim
Output: Same as above.
@node Input from columns
@subsection Input from columns
The columns in a file can be bound to positional replacement strings
using @strong{--colsep}. Here the columns are separated by TAB (\t):
@verbatim
parallel --colsep '\t' echo 1={1} 2={2} :::: tsv-file.tsv
@end verbatim
Output (the order may be different):
@verbatim
1=f1 2=f2
1=A 2=B
1=C 2=D
@end verbatim
@node Header defined replacement strings
@subsection Header defined replacement strings
With @strong{--header} GNU @strong{parallel} will use the first value of the input
source as the name of the replacement string. Only the non-modified
version @strong{@{@}} is supported:
@verbatim
parallel --header : echo f1={f1} f2={f2} ::: f1 A B ::: f2 C D
@end verbatim
Output (the order may be different):
@verbatim
f1=A f2=C
f1=A f2=D
f1=B f2=C
f1=B f2=D
@end verbatim
It is useful with @strong{--colsep} for processing files with TAB separated values:
@verbatim
parallel --header : --colsep '\t' echo f1={f1} f2={f2} \
:::: tsv-file.tsv
@end verbatim
Output (the order may be different):
@verbatim
f1=A f2=B
f1=C f2=D
@end verbatim
@node More pre-defined replacement strings with --plus
@subsection More pre-defined replacement strings with --plus
@strong{--plus} adds the replacement strings @strong{@{+/@} @{+.@} @{+..@} @{+...@} @{..@} @{...@}
@{/..@} @{/...@} @{##@}}. The idea being that @strong{@{+foo@}} matches the opposite of @strong{@{foo@}}
and @strong{@{@}} = @strong{@{+/@}}/@strong{@{/@}} = @strong{@{.@}}.@strong{@{+.@}} = @strong{@{+/@}}/@strong{@{/.@}}.@strong{@{+.@}} = @strong{@{..@}}.@strong{@{+..@}} =
@strong{@{+/@}}/@strong{@{/..@}}.@strong{@{+..@}} = @strong{@{...@}}.@strong{@{+...@}} = @strong{@{+/@}}/@strong{@{/...@}}.@strong{@{+...@}}.
@verbatim
parallel --plus echo {} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {+/}/{/} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {.}.{+.} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {+/}/{/.}.{+.} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {..}.{+..} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {+/}/{/..}.{+..} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {...}.{+...} ::: dir/sub/file.ex1.ex2.ex3
parallel --plus echo {+/}/{/...}.{+...} ::: dir/sub/file.ex1.ex2.ex3
@end verbatim
Output:
@verbatim
dir/sub/file.ex1.ex2.ex3
@end verbatim
@strong{@{##@}} is simply the number of jobs:
@verbatim
parallel --plus echo Job {#} of {##} ::: {1..5}
@end verbatim
Output:
@verbatim
Job 1 of 5
Job 2 of 5
Job 3 of 5
Job 4 of 5
Job 5 of 5
@end verbatim
@node Dynamic replacement strings with --plus
@subsection Dynamic replacement strings with --plus
@strong{--plus} also defines these dynamic replacement strings:
@table @asis
@item @strong{@{:-@emph{string}@}}
@anchor{@strong{@{:-@emph{string}@}}}
Default value is @emph{string} if the argument is empty.
@item @strong{@{:@emph{number}@}}
@anchor{@strong{@{:@emph{number}@}}}
Substring from @emph{number} till end of string.
@item @strong{@{:@emph{number1}:@emph{number2}@}}
@anchor{@strong{@{:@emph{number1}:@emph{number2}@}}}
Substring from @emph{number1} to @emph{number2}.
@item @strong{@{#@emph{string}@}}
@anchor{@strong{@{#@emph{string}@}}}
If the argument starts with @emph{string}, remove it.
@item @strong{@{%@emph{string}@}}
@anchor{@strong{@{%@emph{string}@}}}
If the argument ends with @emph{string}, remove it.
@item @strong{@{/@emph{string1}/@emph{string2}@}}
@anchor{@strong{@{/@emph{string1}/@emph{string2}@}}}
Replace @emph{string1} with @emph{string2}.
@item @strong{@{^@emph{string}@}}
@anchor{@strong{@{^@emph{string}@}}}
If the argument starts with @emph{string}, upper case it. @emph{string} must
be a single letter.
@item @strong{@{^^@emph{string}@}}
@anchor{@strong{@{^^@emph{string}@}}}
If the argument contains @emph{string}, upper case it. @emph{string} must be a
single letter.
@item @strong{@{,@emph{string}@}}
@anchor{@strong{@{@comma{}@emph{string}@}}}
If the argument starts with @emph{string}, lower case it. @emph{string} must
be a single letter.
@item @strong{@{,,@emph{string}@}}
@anchor{@strong{@{@comma{}@comma{}@emph{string}@}}}
If the argument contains @emph{string}, lower case it. @emph{string} must be a
single letter.
@end table
They are inspired from @strong{Bash}:
@verbatim
unset myvar
echo ${myvar:-myval}
parallel --plus echo {:-myval} ::: "$myvar"
myvar=abcAaAdef
echo ${myvar:2}
parallel --plus echo {:2} ::: "$myvar"
echo ${myvar:2:3}
parallel --plus echo {:2:3} ::: "$myvar"
echo ${myvar#bc}
parallel --plus echo {#bc} ::: "$myvar"
echo ${myvar#abc}
parallel --plus echo {#abc} ::: "$myvar"
echo ${myvar%de}
parallel --plus echo {%de} ::: "$myvar"
echo ${myvar%def}
parallel --plus echo {%def} ::: "$myvar"
echo ${myvar/def/ghi}
parallel --plus echo {/def/ghi} ::: "$myvar"
echo ${myvar^a}
parallel --plus echo {^a} ::: "$myvar"
echo ${myvar^^a}
parallel --plus echo {^^a} ::: "$myvar"
myvar=AbcAaAdef
echo ${myvar,A}
parallel --plus echo '{,A}' ::: "$myvar"
echo ${myvar,,A}
parallel --plus echo '{,,A}' ::: "$myvar"
@end verbatim
Output:
@verbatim
myval
myval
cAaAdef
cAaAdef
cAa
cAa
abcAaAdef
abcAaAdef
AaAdef
AaAdef
abcAaAdef
abcAaAdef
abcAaA
abcAaA
abcAaAghi
abcAaAghi
AbcAaAdef
AbcAaAdef
AbcAAAdef
AbcAAAdef
abcAaAdef
abcAaAdef
abcaaadef
abcaaadef
@end verbatim
@node More than one argument
@section More than one argument
With @strong{--xargs} GNU @strong{parallel} will fit as many arguments as possible on a
single line:
@verbatim
cat num30000 | parallel --xargs echo | wc -l
@end verbatim
Output (if you run this under Bash on GNU/Linux):
@verbatim
2
@end verbatim
The 30000 arguments fitted on 2 lines.
The maximal length of a single line can be set with @strong{-s}. With a maximal
line length of 10000 chars 17 commands will be run:
@verbatim
cat num30000 | parallel --xargs -s 10000 echo | wc -l
@end verbatim
Output:
@verbatim
17
@end verbatim
For better parallelism GNU @strong{parallel} can distribute the arguments
between all the parallel jobs when end of file is met.
Below GNU @strong{parallel} reads the last argument when generating the second
job. When GNU @strong{parallel} reads the last argument, it spreads all the
arguments for the second job over 4 jobs instead, as 4 parallel jobs
are requested.
The first job will be the same as the @strong{--xargs} example above, but the
second job will be split into 4 evenly sized jobs, resulting in a
total of 5 jobs:
@verbatim
cat num30000 | parallel --jobs 4 -m echo | wc -l
@end verbatim
Output (if you run this under Bash on GNU/Linux):
@verbatim
5
@end verbatim
This is even more visible when running 4 jobs with 10 arguments. The
10 arguments are being spread over 4 jobs:
@verbatim
parallel --jobs 4 -m echo ::: 1 2 3 4 5 6 7 8 9 10
@end verbatim
Output:
@verbatim
1 2 3
4 5 6
7 8 9
10
@end verbatim
A replacement string can be part of a word. @strong{-m} will not repeat the context:
@verbatim
parallel --jobs 4 -m echo pre-{}-post ::: A B C D E F G
@end verbatim
Output (the order may be different):
@verbatim
pre-A B-post
pre-C D-post
pre-E F-post
pre-G-post
@end verbatim
To repeat the context use @strong{-X} which otherwise works like @strong{-m}:
@verbatim
parallel --jobs 4 -X echo pre-{}-post ::: A B C D E F G
@end verbatim
Output (the order may be different):
@verbatim
pre-A-post pre-B-post
pre-C-post pre-D-post
pre-E-post pre-F-post
pre-G-post
@end verbatim
To limit the number of arguments use @strong{-N}:
@verbatim
parallel -N3 echo ::: A B C D E F G H
@end verbatim
Output (the order may be different):
@verbatim
A B C
D E F
G H
@end verbatim
@strong{-N} also sets the positional replacement strings:
@verbatim
parallel -N3 echo 1={1} 2={2} 3={3} ::: A B C D E F G H
@end verbatim
Output (the order may be different):
@verbatim
1=A 2=B 3=C
1=D 2=E 3=F
1=G 2=H 3=
@end verbatim
@strong{-N0} reads 1 argument but inserts none:
@verbatim
parallel -N0 echo foo ::: 1 2 3
@end verbatim
Output:
@verbatim
foo
foo
foo
@end verbatim
@node Quoting
@section Quoting
Command lines that contain special characters may need to be protected from the shell.
The @strong{perl} program @strong{print "@@ARGV\n"} basically works like @strong{echo}.
@verbatim
perl -e 'print "@ARGV\n"' A
@end verbatim
Output:
@verbatim
A
@end verbatim
To run that in parallel the command needs to be quoted:
@verbatim
parallel perl -e 'print "@ARGV\n"' ::: This wont work
@end verbatim
Output:
@verbatim
[Nothing]
@end verbatim
To quote the command use @strong{-q}:
@verbatim
parallel -q perl -e 'print "@ARGV\n"' ::: This works
@end verbatim
Output (the order may be different):
@verbatim
This
works
@end verbatim
Or you can quote the critical part using @strong{\'}:
@verbatim
parallel perl -e \''print "@ARGV\n"'\' ::: This works, too
@end verbatim
Output (the order may be different):
@verbatim
This
works,
too
@end verbatim
GNU @strong{parallel} can also \-quote full lines. Simply run this:
@verbatim
parallel --shellquote
Warning: Input is read from the terminal. You either know what you
Warning: are doing (in which case: YOU ARE AWESOME!) or you forgot
Warning: ::: or :::: or to pipe data into parallel. If so
Warning: consider going through the tutorial: man parallel_tutorial
Warning: Press CTRL-D to exit.
perl -e 'print "@ARGV\n"'
[CTRL-D]
@end verbatim
Output:
@verbatim
perl\ -e\ \'print\ \"@ARGV\\n\"\'
@end verbatim
This can then be used as the command:
@verbatim
parallel perl\ -e\ \'print\ \"@ARGV\\n\"\' ::: This also works
@end verbatim
Output (the order may be different):
@verbatim
This
also
works
@end verbatim
@node Trimming space
@section Trimming space
Space can be trimmed on the arguments using @strong{--trim}:
@verbatim
parallel --trim r echo pre-{}-post ::: ' A '
@end verbatim
Output:
@verbatim
pre- A-post
@end verbatim
To trim on the left side:
@verbatim
parallel --trim l echo pre-{}-post ::: ' A '
@end verbatim
Output:
@verbatim
pre-A -post
@end verbatim
To trim on the both sides:
@verbatim
parallel --trim lr echo pre-{}-post ::: ' A '
@end verbatim
Output:
@verbatim
pre-A-post
@end verbatim
@node Respecting the shell
@section Respecting the shell
This tutorial uses Bash as the shell. GNU @strong{parallel} respects which
shell you are using, so in @strong{zsh} you can do:
@verbatim
parallel echo \={} ::: zsh bash ls
@end verbatim
Output:
@verbatim
/usr/bin/zsh
/bin/bash
/bin/ls
@end verbatim
In @strong{csh} you can do:
@verbatim
parallel 'set a="{}"; if( { test -d "$a" } ) echo "$a is a dir"' ::: *
@end verbatim
Output:
@verbatim
[somedir] is a dir
@end verbatim
This also becomes useful if you use GNU @strong{parallel} in a shell script:
GNU @strong{parallel} will use the same shell as the shell script.
@node Controlling the output
@chapter Controlling the output
The output can prefixed with the argument:
@verbatim
parallel --tag echo foo-{} ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
A foo-A
B foo-B
C foo-C
@end verbatim
To prefix it with another string use @strong{--tagstring}:
@verbatim
parallel --tagstring {}-bar echo foo-{} ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
A-bar foo-A
B-bar foo-B
C-bar foo-C
@end verbatim
To see what commands will be run without running them use @strong{--dryrun}:
@verbatim
parallel --dryrun echo {} ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
echo A
echo B
echo C
@end verbatim
To print the command before running them use @strong{--verbose}:
@verbatim
parallel --verbose echo {} ::: A B C
@end verbatim
Output (the order may be different):
@verbatim
echo A
echo B
A
echo C
B
C
@end verbatim
GNU @strong{parallel} will postpone the output until the command completes:
@verbatim
parallel -j2 'printf "%s-start\n%s" {} {};
sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1
@end verbatim
Output:
@verbatim
2-start
2-middle
2-end
1-start
1-middle
1-end
4-start
4-middle
4-end
@end verbatim
To get the output immediately use @strong{--ungroup}:
@verbatim
parallel -j2 --ungroup 'printf "%s-start\n%s" {} {};
sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1
@end verbatim
Output:
@verbatim
4-start
42-start
2-middle
2-end
1-start
1-middle
1-end
-middle
4-end
@end verbatim
@strong{--ungroup} is fast, but can cause half a line from one job to be mixed
with half a line of another job. That has happened in the second line,
where the line '4-middle' is mixed with '2-start'.
To avoid this use @strong{--linebuffer}:
@verbatim
parallel -j2 --linebuffer 'printf "%s-start\n%s" {} {};
sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1
@end verbatim
Output:
@verbatim
4-start
2-start
2-middle
2-end
1-start
1-middle
1-end
4-middle
4-end
@end verbatim
To force the output in the same order as the arguments use @strong{--keep-order}/@strong{-k}:
@verbatim
parallel -j2 -k 'printf "%s-start\n%s" {} {};
sleep {};printf "%s\n" -middle;echo {}-end' ::: 4 2 1
@end verbatim
Output:
@verbatim
4-start
4-middle
4-end
2-start
2-middle
2-end
1-start
1-middle
1-end
@end verbatim
@menu
* Saving output into files::
@end menu
@node Saving output into files
@section Saving output into files
GNU @strong{parallel} can save the output of each job into files:
@verbatim
parallel --files echo ::: A B C
@end verbatim
Output will be similar to this:
@verbatim
/tmp/pAh6uWuQCg.par
/tmp/opjhZCzAX4.par
/tmp/W0AT_Rph2o.par
@end verbatim
By default GNU @strong{parallel} will cache the output in files in @strong{/tmp}. This
can be changed by setting @strong{$TMPDIR} or @strong{--tmpdir}:
@verbatim
parallel --tmpdir /var/tmp --files echo ::: A B C
@end verbatim
Output will be similar to this:
@verbatim
/var/tmp/N_vk7phQRc.par
/var/tmp/7zA4Ccf3wZ.par
/var/tmp/LIuKgF_2LP.par
@end verbatim
Or:
@verbatim
TMPDIR=/var/tmp parallel --files echo ::: A B C
@end verbatim
Output: Same as above.
The output files can be saved in a structured way using @strong{--results}:
@verbatim
parallel --results outdir echo ::: A B C
@end verbatim
Output:
@verbatim
A
B
C
@end verbatim
These files were also generated containing the standard output
(stdout), standard error (stderr), and the sequence number (seq):
@verbatim
outdir/1/A/seq
outdir/1/A/stderr
outdir/1/A/stdout
outdir/1/B/seq
outdir/1/B/stderr
outdir/1/B/stdout
outdir/1/C/seq
outdir/1/C/stderr
outdir/1/C/stdout
@end verbatim
@strong{--header :} will take the first value as name and use that in the
directory structure. This is useful if you are using multiple input
sources:
@verbatim
parallel --header : --results outdir echo ::: f1 A B ::: f2 C D
@end verbatim
Generated files:
@verbatim
outdir/f1/A/f2/C/seq
outdir/f1/A/f2/C/stderr
outdir/f1/A/f2/C/stdout
outdir/f1/A/f2/D/seq
outdir/f1/A/f2/D/stderr
outdir/f1/A/f2/D/stdout
outdir/f1/B/f2/C/seq
outdir/f1/B/f2/C/stderr
outdir/f1/B/f2/C/stdout
outdir/f1/B/f2/D/seq
outdir/f1/B/f2/D/stderr
outdir/f1/B/f2/D/stdout
@end verbatim
The directories are named after the variables and their values.
@node Controlling the execution
@chapter Controlling the execution
@menu
* Number of simultaneous jobs::
* Shuffle job order::
* Interactivity::
* A terminal for every job::
* Timing::
* Progress information::
* Termination::
* Limiting the resources::
@end menu
@node Number of simultaneous jobs
@section Number of simultaneous jobs
The number of concurrent jobs is given with @strong{--jobs}/@strong{-j}:
@verbatim
/usr/bin/time parallel -N0 -j64 sleep 1 :::: num128
@end verbatim
With 64 jobs in parallel the 128 @strong{sleep}s will take 2-8 seconds to run -
depending on how fast your machine is.
By default @strong{--jobs} is the same as the number of CPU cores. So this:
@verbatim
/usr/bin/time parallel -N0 sleep 1 :::: num128
@end verbatim
should take twice the time of running 2 jobs per CPU core:
@verbatim
/usr/bin/time parallel -N0 --jobs 200% sleep 1 :::: num128
@end verbatim
@strong{--jobs 0} will run as many jobs in parallel as possible:
@verbatim
/usr/bin/time parallel -N0 --jobs 0 sleep 1 :::: num128
@end verbatim
which should take 1-7 seconds depending on how fast your machine is.
@strong{--jobs} can read from a file which is re-read when a job finishes:
@verbatim
echo 50% > my_jobs
/usr/bin/time parallel -N0 --jobs my_jobs sleep 1 :::: num128 &
sleep 1
echo 0 > my_jobs
wait
@end verbatim
The first second only 50% of the CPU cores will run a job. Then @strong{0} is
put into @strong{my_jobs} and then the rest of the jobs will be started in
parallel.
Instead of basing the percentage on the number of CPU cores
GNU @strong{parallel} can base it on the number of CPUs:
@verbatim
parallel --use-cpus-instead-of-cores -N0 sleep 1 :::: num8
@end verbatim
@node Shuffle job order
@section Shuffle job order
If you have many jobs (e.g. by multiple combinations of input
sources), it can be handy to shuffle the jobs, so you get different
values run. Use @strong{--shuf} for that:
@verbatim
parallel --shuf echo ::: 1 2 3 ::: a b c ::: A B C
@end verbatim
Output:
@verbatim
All combinations but different order for each run.
@end verbatim
@node Interactivity
@section Interactivity
GNU @strong{parallel} can ask the user if a command should be run using @strong{--interactive}:
@verbatim
parallel --interactive echo ::: 1 2 3
@end verbatim
Output:
@verbatim
echo 1 ?...y
echo 2 ?...n
1
echo 3 ?...y
3
@end verbatim
GNU @strong{parallel} can be used to put arguments on the command line for an
interactive command such as @strong{emacs} to edit one file at a time:
@verbatim
parallel --tty emacs ::: 1 2 3
@end verbatim
Or give multiple argument in one go to open multiple files:
@verbatim
parallel -X --tty vi ::: 1 2 3
@end verbatim
@node A terminal for every job
@section A terminal for every job
Using @strong{--tmux} GNU @strong{parallel} can start a terminal for every job run:
@verbatim
seq 10 20 | parallel --tmux 'echo start {}; sleep {}; echo done {}'
@end verbatim
This will tell you to run something similar to:
@verbatim
tmux -S /tmp/tmsrPrO0 attach
@end verbatim
Using normal @strong{tmux} keystrokes (CTRL-b n or CTRL-b p) you can cycle
between windows of the running jobs. When a job is finished it will
pause for 10 seconds before closing the window.
@node Timing
@section Timing
Some jobs do heavy I/O when they start. To avoid a thundering herd GNU
@strong{parallel} can delay starting new jobs. @strong{--delay} @emph{X} will make
sure there is at least @emph{X} seconds between each start:
@verbatim
parallel --delay 2.5 echo Starting {}\;date ::: 1 2 3
@end verbatim
Output:
@verbatim
Starting 1
Thu Aug 15 16:24:33 CEST 2013
Starting 2
Thu Aug 15 16:24:35 CEST 2013
Starting 3
Thu Aug 15 16:24:38 CEST 2013
@end verbatim
If jobs taking more than a certain amount of time are known to fail,
they can be stopped with @strong{--timeout}. The accuracy of @strong{--timeout} is
2 seconds:
@verbatim
parallel --timeout 4.1 sleep {}\; echo {} ::: 2 4 6 8
@end verbatim
Output:
@verbatim
2
4
@end verbatim
GNU @strong{parallel} can compute the median runtime for jobs and kill those
that take more than 200% of the median runtime:
@verbatim
parallel --timeout 200% sleep {}\; echo {} ::: 2.1 2.2 3 7 2.3
@end verbatim
Output:
@verbatim
2.1
2.2
3
2.3
@end verbatim
@node Progress information
@section Progress information
Based on the runtime of completed jobs GNU @strong{parallel} can estimate the
total runtime:
@verbatim
parallel --eta sleep ::: 1 3 2 2 1 3 3 2 1
@end verbatim
Output:
@verbatim
Computers / CPU cores / Max jobs to run
1:local / 2 / 2
Computer:jobs running/jobs completed/%of started jobs/
Average seconds to complete
ETA: 2s 0left 1.11avg local:0/9/100%/1.1s
@end verbatim
GNU @strong{parallel} can give progress information with @strong{--progress}:
@verbatim
parallel --progress sleep ::: 1 3 2 2 1 3 3 2 1
@end verbatim
Output:
@verbatim
Computers / CPU cores / Max jobs to run
1:local / 2 / 2
Computer:jobs running/jobs completed/%of started jobs/
Average seconds to complete
local:0/9/100%/1.1s
@end verbatim
A progress bar can be shown with @strong{--bar}:
@verbatim
parallel --bar sleep ::: 1 3 2 2 1 3 3 2 1
@end verbatim
And a graphic bar can be shown with @strong{--bar} and @strong{zenity}:
@verbatim
seq 1000 | parallel -j10 --bar '(echo -n {};sleep 0.1)' \
2> >(perl -pe 'BEGIN{$/="\r";$|=1};s/\r/\n/g' |
zenity --progress --auto-kill --auto-close)
@end verbatim
A logfile of the jobs completed so far can be generated with @strong{--joblog}:
@verbatim
parallel --joblog /tmp/log exit ::: 1 2 3 0
cat /tmp/log
@end verbatim
Output:
@verbatim
Seq Host Starttime Runtime Send Receive Exitval Signal Command
1 : 1376577364.974 0.008 0 0 1 0 exit 1
2 : 1376577364.982 0.013 0 0 2 0 exit 2
3 : 1376577364.990 0.013 0 0 3 0 exit 3
4 : 1376577365.003 0.003 0 0 0 0 exit 0
@end verbatim
The log contains the job sequence, which host the job was run on, the
start time and run time, how much data was transferred, the exit
value, the signal that killed the job, and finally the command being
run.
With a joblog GNU @strong{parallel} can be stopped and later pickup where it
left off. It it important that the input of the completed jobs is
unchanged.
@verbatim
parallel --joblog /tmp/log exit ::: 1 2 3 0
cat /tmp/log
parallel --resume --joblog /tmp/log exit ::: 1 2 3 0 0 0
cat /tmp/log
@end verbatim
Output:
@verbatim
Seq Host Starttime Runtime Send Receive Exitval Signal Command
1 : 1376580069.544 0.008 0 0 1 0 exit 1
2 : 1376580069.552 0.009 0 0 2 0 exit 2
3 : 1376580069.560 0.012 0 0 3 0 exit 3
4 : 1376580069.571 0.005 0 0 0 0 exit 0
Seq Host Starttime Runtime Send Receive Exitval Signal Command
1 : 1376580069.544 0.008 0 0 1 0 exit 1
2 : 1376580069.552 0.009 0 0 2 0 exit 2
3 : 1376580069.560 0.012 0 0 3 0 exit 3
4 : 1376580069.571 0.005 0 0 0 0 exit 0
5 : 1376580070.028 0.009 0 0 0 0 exit 0
6 : 1376580070.038 0.007 0 0 0 0 exit 0
@end verbatim
Note how the start time of the last 2 jobs is clearly different from the second run.
With @strong{--resume-failed} GNU @strong{parallel} will re-run the jobs that failed:
@verbatim
parallel --resume-failed --joblog /tmp/log exit ::: 1 2 3 0 0 0
cat /tmp/log
@end verbatim
Output:
@verbatim
Seq Host Starttime Runtime Send Receive Exitval Signal Command
1 : 1376580069.544 0.008 0 0 1 0 exit 1
2 : 1376580069.552 0.009 0 0 2 0 exit 2
3 : 1376580069.560 0.012 0 0 3 0 exit 3
4 : 1376580069.571 0.005 0 0 0 0 exit 0
5 : 1376580070.028 0.009 0 0 0 0 exit 0
6 : 1376580070.038 0.007 0 0 0 0 exit 0
1 : 1376580154.433 0.010 0 0 1 0 exit 1
2 : 1376580154.444 0.022 0 0 2 0 exit 2
3 : 1376580154.466 0.005 0 0 3 0 exit 3
@end verbatim
Note how seq 1 2 3 have been repeated because they had exit value
different from 0.
@strong{--retry-failed} does almost the same as @strong{--resume-failed}. Where
@strong{--resume-failed} reads the commands from the command line (and
ignores the commands in the joblog), @strong{--retry-failed} ignores the
command line and reruns the commands mentioned in the joblog.
@verbatim
parallel --retry-failed --joblog /tmp/log
cat /tmp/log
@end verbatim
Output:
@verbatim
Seq Host Starttime Runtime Send Receive Exitval Signal Command
1 : 1376580069.544 0.008 0 0 1 0 exit 1
2 : 1376580069.552 0.009 0 0 2 0 exit 2
3 : 1376580069.560 0.012 0 0 3 0 exit 3
4 : 1376580069.571 0.005 0 0 0 0 exit 0
5 : 1376580070.028 0.009 0 0 0 0 exit 0
6 : 1376580070.038 0.007 0 0 0 0 exit 0
1 : 1376580154.433 0.010 0 0 1 0 exit 1
2 : 1376580154.444 0.022 0 0 2 0 exit 2
3 : 1376580154.466 0.005 0 0 3 0 exit 3
1 : 1376580164.633 0.010 0 0 1 0 exit 1
2 : 1376580164.644 0.022 0 0 2 0 exit 2
3 : 1376580164.666 0.005 0 0 3 0 exit 3
@end verbatim
@node Termination
@section Termination
@menu
* Unconditional termination::
* Termination dependent on job status::
* Termination signals (advanced)::
@end menu
@node Unconditional termination
@subsection Unconditional termination
By default GNU @strong{parallel} will wait for all jobs to finish before exiting.
If you send GNU @strong{parallel} the @strong{TERM} signal, GNU @strong{parallel} will
stop spawning new jobs and wait for the remaining jobs to finish. If
you send GNU @strong{parallel} the @strong{TERM} signal again, GNU @strong{parallel}
will kill all running jobs and exit.
@node Termination dependent on job status
@subsection Termination dependent on job status
For certain jobs there is no need to continue if one of the jobs fails
and has an exit code different from 0. GNU @strong{parallel} will stop spawning new jobs
with @strong{--halt soon,fail=1}:
@verbatim
parallel -j2 --halt soon,fail=1 echo {}\; exit {} ::: 0 0 1 2 3
@end verbatim
Output:
@verbatim
0
0
1
parallel: This job failed:
echo 1; exit 1
parallel: Starting no more jobs. Waiting for 1 jobs to finish.
2
@end verbatim
With @strong{--halt now,fail=1} the running jobs will be killed immediately:
@verbatim
parallel -j2 --halt now,fail=1 echo {}\; exit {} ::: 0 0 1 2 3
@end verbatim
Output:
@verbatim
0
0
1
parallel: This job failed:
echo 1; exit 1
@end verbatim
If @strong{--halt} is given a percentage this percentage of the jobs must fail
before GNU @strong{parallel} stops spawning more jobs:
@verbatim
parallel -j2 --halt soon,fail=20% echo {}\; exit {} \
::: 0 1 2 3 4 5 6 7 8 9
@end verbatim
Output:
@verbatim
0
1
parallel: This job failed:
echo 1; exit 1
2
parallel: This job failed:
echo 2; exit 2
parallel: Starting no more jobs. Waiting for 1 jobs to finish.
3
parallel: This job failed:
echo 3; exit 3
@end verbatim
If you are looking for success instead of failures, you can use
@strong{success}. This will finish as soon as the first job succeeds:
@verbatim
parallel -j2 --halt now,success=1 echo {}\; exit {} ::: 1 2 3 0 4 5 6
@end verbatim
Output:
@verbatim
1
2
3
0
parallel: This job succeeded:
echo 0; exit 0
@end verbatim
GNU @strong{parallel} can retry the command with @strong{--retries}. This is useful if a
command fails for unknown reasons now and then.
@verbatim
parallel -k --retries 3 \
'echo tried {} >>/tmp/runs; echo completed {}; exit {}' ::: 1 2 0
cat /tmp/runs
@end verbatim
Output:
@verbatim
completed 1
completed 2
completed 0
tried 1
tried 2
tried 1
tried 2
tried 1
tried 2
tried 0
@end verbatim
Note how job 1 and 2 were tried 3 times, but 0 was not retried because it had exit code 0.
@node Termination signals (advanced)
@subsection Termination signals (advanced)
Using @strong{--termseq} you can control which signals are sent when killing
children. Normally children will be killed by sending them @strong{SIGTERM},
waiting 200 ms, then another @strong{SIGTERM}, waiting 100 ms, then another
@strong{SIGTERM}, waiting 50 ms, then a @strong{SIGKILL}, finally waiting 25 ms
before giving up. It looks like this:
@verbatim
show_signals() {
perl -e 'for(keys %SIG) {
$SIG{$_} = eval "sub { print \"Got $_\\n\"; }";
}
while(1){sleep 1}'
}
export -f show_signals
echo | parallel --termseq TERM,200,TERM,100,TERM,50,KILL,25 \
-u --timeout 1 show_signals
@end verbatim
Output:
@verbatim
Got TERM
Got TERM
Got TERM
@end verbatim
Or just:
@verbatim
echo | parallel -u --timeout 1 show_signals
@end verbatim
Output: Same as above.
You can change this to @strong{SIGINT}, @strong{SIGTERM}, @strong{SIGKILL}:
@verbatim
echo | parallel --termseq INT,200,TERM,100,KILL,25 \
-u --timeout 1 show_signals
@end verbatim
Output:
@verbatim
Got INT
Got TERM
@end verbatim
The @strong{SIGKILL} does not show because it cannot be caught, and thus the
child dies.
@node Limiting the resources
@section Limiting the resources
To avoid overloading systems GNU @strong{parallel} can look at the system load
before starting another job:
@verbatim
parallel --load 100% echo load is less than {} job per cpu ::: 1
@end verbatim
Output:
@verbatim
[when then load is less than the number of cpu cores]
load is less than 1 job per cpu
@end verbatim
GNU @strong{parallel} can also check if the system is swapping.
@verbatim
parallel --noswap echo the system is not swapping ::: now
@end verbatim
Output:
@verbatim
[when then system is not swapping]
the system is not swapping now
@end verbatim
Some jobs need a lot of memory, and should only be started when there
is enough memory free. Using @strong{--memfree} GNU @strong{parallel} can check if
there is enough memory free. Additionally, GNU @strong{parallel} will kill
off the youngest job if the memory free falls below 50% of the
size. The killed job will put back on the queue and retried later.
@verbatim
parallel --memfree 1G echo will run if more than 1 GB is ::: free
@end verbatim
GNU @strong{parallel} can run the jobs with a nice value. This will work both
locally and remotely.
@verbatim
parallel --nice 17 echo this is being run with nice -n ::: 17
@end verbatim
Output:
@verbatim
this is being run with nice -n 17
@end verbatim
@node Remote execution
@chapter Remote execution
GNU @strong{parallel} can run jobs on remote servers. It uses @strong{ssh} to
communicate with the remote machines.
@menu
* Sshlogin::
* Transferring files::
* Working dir::
* Avoid overloading sshd::
* Ignore hosts that are down::
* Running the same commands on all hosts::
* Transferring environment variables and functions::
* Showing what is actually run::
@end menu
@node Sshlogin
@section Sshlogin
The most basic sshlogin is @strong{-S} @emph{host}:
@verbatim
parallel -S $SERVER1 echo running on ::: $SERVER1
@end verbatim
Output:
@verbatim
running on [$SERVER1]
@end verbatim
To use a different username prepend the server with @emph{username@@}:
@verbatim
parallel -S username@$SERVER1 echo running on ::: username@$SERVER1
@end verbatim
Output:
@verbatim
running on [username@$SERVER1]
@end verbatim
The special sshlogin @strong{:} is the local machine:
@verbatim
parallel -S : echo running on ::: the_local_machine
@end verbatim
Output:
@verbatim
running on the_local_machine
@end verbatim
If @strong{ssh} is not in $PATH it can be prepended to $SERVER1:
@verbatim
parallel -S '/usr/bin/ssh '$SERVER1 echo custom ::: ssh
@end verbatim
Output:
@verbatim
custom ssh
@end verbatim
The @strong{ssh} command can also be given using @strong{--ssh}:
@verbatim
parallel --ssh /usr/bin/ssh -S $SERVER1 echo custom ::: ssh
@end verbatim
or by setting @strong{$PARALLEL_SSH}:
@verbatim
export PARALLEL_SSH=/usr/bin/ssh
parallel -S $SERVER1 echo custom ::: ssh
@end verbatim
Several servers can be given using multiple @strong{-S}:
@verbatim
parallel -S $SERVER1 -S $SERVER2 echo ::: running on more hosts
@end verbatim
Output (the order may be different):
@verbatim
running
on
more
hosts
@end verbatim
Or they can be separated by @strong{,}:
@verbatim
parallel -S $SERVER1,$SERVER2 echo ::: running on more hosts
@end verbatim
Output: Same as above.
Or newline:
@verbatim
# This gives a \n between $SERVER1 and $SERVER2
SERVERS="`echo $SERVER1; echo $SERVER2`"
parallel -S "$SERVERS" echo ::: running on more hosts
@end verbatim
They can also be read from a file (replace @emph{user@@} with the user on @strong{$SERVER2}):
@verbatim
echo $SERVER1 > nodefile
# Force 4 cores, special ssh-command, username
echo 4//usr/bin/ssh user@$SERVER2 >> nodefile
parallel --sshloginfile nodefile echo ::: running on more hosts
@end verbatim
Output: Same as above.
Every time a job finished, the @strong{--sshloginfile} will be re-read, so
it is possible to both add and remove hosts while running.
The special @strong{--sshloginfile ..} reads from @strong{~/.parallel/sshloginfile}.
To force GNU @strong{parallel} to treat a server having a given number of CPU
cores prepend the number of core followed by @strong{/} to the sshlogin:
@verbatim
parallel -S 4/$SERVER1 echo force {} cpus on server ::: 4
@end verbatim
Output:
@verbatim
force 4 cpus on server
@end verbatim
Servers can be put into groups by prepending @emph{@@groupname} to the
server and the group can then be selected by appending @emph{@@groupname} to
the argument if using @strong{--hostgroup}:
@verbatim
parallel --hostgroup -S @grp1/$SERVER1 -S @grp2/$SERVER2 echo {} \
::: run_on_grp1@grp1 run_on_grp2@grp2
@end verbatim
Output:
@verbatim
run_on_grp1
run_on_grp2
@end verbatim
A host can be in multiple groups by separating the groups with @strong{+}, and
you can force GNU @strong{parallel} to limit the groups on which the command
can be run with @strong{-S} @emph{@@groupname}:
@verbatim
parallel -S @grp1 -S @grp1+grp2/$SERVER1 -S @grp2/SERVER2 echo {} \
::: run_on_grp1 also_grp1
@end verbatim
Output:
@verbatim
run_on_grp1
also_grp1
@end verbatim
@node Transferring files
@section Transferring files
GNU @strong{parallel} can transfer the files to be processed to the remote
host. It does that using rsync.
@verbatim
echo This is input_file > input_file
parallel -S $SERVER1 --transferfile {} cat ::: input_file
@end verbatim
Output:
@verbatim
This is input_file
@end verbatim
If the files are processed into another file, the resulting file can be
transferred back:
@verbatim
echo This is input_file > input_file
parallel -S $SERVER1 --transferfile {} --return {}.out \
cat {} ">"{}.out ::: input_file
cat input_file.out
@end verbatim
Output: Same as above.
To remove the input and output file on the remote server use @strong{--cleanup}:
@verbatim
echo This is input_file > input_file
parallel -S $SERVER1 --transferfile {} --return {}.out --cleanup \
cat {} ">"{}.out ::: input_file
cat input_file.out
@end verbatim
Output: Same as above.
There is a shorthand for @strong{--transferfile @{@} --return --cleanup} called @strong{--trc}:
@verbatim
echo This is input_file > input_file
parallel -S $SERVER1 --trc {}.out cat {} ">"{}.out ::: input_file
cat input_file.out
@end verbatim
Output: Same as above.
Some jobs need a common database for all jobs. GNU @strong{parallel} can
transfer that using @strong{--basefile} which will transfer the file before the
first job:
@verbatim
echo common data > common_file
parallel --basefile common_file -S $SERVER1 \
cat common_file\; echo {} ::: foo
@end verbatim
Output:
@verbatim
common data
foo
@end verbatim
To remove it from the remote host after the last job use @strong{--cleanup}.
@node Working dir
@section Working dir
The default working dir on the remote machines is the login dir. This
can be changed with @strong{--workdir} @emph{mydir}.
Files transferred using @strong{--transferfile} and @strong{--return} will be relative
to @emph{mydir} on remote computers, and the command will be executed in
the dir @emph{mydir}.
The special @emph{mydir} value @strong{...} will create working dirs under
@strong{~/.parallel/tmp} on the remote computers. If @strong{--cleanup} is given
these dirs will be removed.
The special @emph{mydir} value @strong{.} uses the current working dir. If the
current working dir is beneath your home dir, the value @strong{.} is
treated as the relative path to your home dir. This means that if your
home dir is different on remote computers (e.g. if your login is
different) the relative path will still be relative to your home dir.
@verbatim
parallel -S $SERVER1 pwd ::: ""
parallel --workdir . -S $SERVER1 pwd ::: ""
parallel --workdir ... -S $SERVER1 pwd ::: ""
@end verbatim
Output:
@verbatim
[the login dir on $SERVER1]
[current dir relative on $SERVER1]
[a dir in ~/.parallel/tmp/...]
@end verbatim
@node Avoid overloading sshd
@section Avoid overloading sshd
If many jobs are started on the same server, @strong{sshd} can be
overloaded. GNU @strong{parallel} can insert a delay between each job run on
the same server:
@verbatim
parallel -S $SERVER1 --sshdelay 0.2 echo ::: 1 2 3
@end verbatim
Output (the order may be different):
@verbatim
1
2
3
@end verbatim
@strong{sshd} will be less overloaded if using @strong{--controlmaster}, which will
multiplex ssh connections:
@verbatim
parallel --controlmaster -S $SERVER1 echo ::: 1 2 3
@end verbatim
Output: Same as above.
@node Ignore hosts that are down
@section Ignore hosts that are down
In clusters with many hosts a few of them are often down. GNU @strong{parallel}
can ignore those hosts. In this case the host 173.194.32.46 is down:
@verbatim
parallel --filter-hosts -S 173.194.32.46,$SERVER1 echo ::: bar
@end verbatim
Output:
@verbatim
bar
@end verbatim
@node Running the same commands on all hosts
@section Running the same commands on all hosts
GNU @strong{parallel} can run the same command on all the hosts:
@verbatim
parallel --onall -S $SERVER1,$SERVER2 echo ::: foo bar
@end verbatim
Output (the order may be different):
@verbatim
foo
bar
foo
bar
@end verbatim
Often you will just want to run a single command on all hosts with out
arguments. @strong{--nonall} is a no argument @strong{--onall}:
@verbatim
parallel --nonall -S $SERVER1,$SERVER2 echo foo bar
@end verbatim
Output:
@verbatim
foo bar
foo bar
@end verbatim
When @strong{--tag} is used with @strong{--nonall} and @strong{--onall} the @strong{--tagstring} is the host:
@verbatim
parallel --nonall --tag -S $SERVER1,$SERVER2 echo foo bar
@end verbatim
Output (the order may be different):
@verbatim
$SERVER1 foo bar
$SERVER2 foo bar
@end verbatim
@strong{--jobs} sets the number of servers to log in to in parallel.
@node Transferring environment variables and functions
@section Transferring environment variables and functions
@strong{env_parallel} is a shell function that transfers all aliases,
functions, variables, and arrays. You active it by running:
@verbatim
source `which env_parallel.bash`
@end verbatim
Replace @strong{bash} with the shell you use.
Now you can use @strong{env_parallel} instead of @strong{parallel} and still have
your environment:
@verbatim
alias myecho=echo
myvar="Joe's var is"
env_parallel -S $SERVER1 'myecho $myvar' ::: green
@end verbatim
Output:
@verbatim
Joe's var is green
@end verbatim
The disadvantage is that if your environment is huge @strong{env_parallel}
will fail.
When @strong{env_parallel} fails, you can still use @strong{--env} to tell GNU
@strong{parallel} to transfer an environment variable to the remote system.
@verbatim
MYVAR='foo bar'
export MYVAR
parallel --env MYVAR -S $SERVER1 echo '$MYVAR' ::: baz
@end verbatim
Output:
@verbatim
foo bar baz
@end verbatim
This works for functions, too, if your shell is Bash:
@verbatim
# This only works in Bash
my_func() {
echo in my_func $1
}
export -f my_func
parallel --env my_func -S $SERVER1 my_func ::: baz
@end verbatim
Output:
@verbatim
in my_func baz
@end verbatim
GNU @strong{parallel} can copy all user defined variables and functions to
the remote system. It just needs to record which ones to ignore in
@strong{~/.parallel/ignored_vars}. Do that by running this once:
@verbatim
parallel --record-env
cat ~/.parallel/ignored_vars
@end verbatim
Output:
@verbatim
[list of variables to ignore - including $PATH and $HOME]
@end verbatim
Now all other variables and functions defined will be copied when
using @strong{--env _}.
@verbatim
# The function is only copied if using Bash
my_func2() {
echo in my_func2 $VAR $1
}
export -f my_func2
VAR=foo
export VAR
parallel --env _ -S $SERVER1 'echo $VAR; my_func2' ::: bar
@end verbatim
Output:
@verbatim
foo
in my_func2 foo bar
@end verbatim
If you use @strong{env_parallel} the variables, functions, and aliases do
not even need to be exported to be copied:
@verbatim
NOT='not exported var'
alias myecho=echo
not_ex() {
myecho in not_exported_func $NOT $1
}
env_parallel --env _ -S $SERVER1 'echo $NOT; not_ex' ::: bar
@end verbatim
Output:
@verbatim
not exported var
in not_exported_func not exported var bar
@end verbatim
@node Showing what is actually run
@section Showing what is actually run
@strong{--verbose} will show the command that would be run on the local
machine.
When using @strong{--cat}, @strong{--pipepart}, or when a job is run on a remote
machine, the command is wrapped with helper scripts. @strong{-vv} shows all
of this.
@verbatim
parallel -vv --pipepart --block 1M wc :::: num30000
@end verbatim
Output:
@verbatim
<num30000 perl -e 'while(@ARGV) { sysseek(STDIN,shift,0) || die;
$left = shift; while($read = sysread(STDIN,$buf, ($left > 131072
? 131072 : $left))){ $left -= $read; syswrite(STDOUT,$buf); } }'
0 0 0 168894 | (wc)
30000 30000 168894
@end verbatim
When the command gets more complex, the output is so hard to read,
that it is only useful for debugging:
@verbatim
my_func3() {
echo in my_func $1 > $1.out
}
export -f my_func3
parallel -vv --workdir ... --nice 17 --env _ --trc {}.out \
-S $SERVER1 my_func3 {} ::: abc-file
@end verbatim
Output will be similar to:
@verbatim
( ssh server -- mkdir -p ./.parallel/tmp/aspire-1928520-1;rsync
--protocol 30 -rlDzR -essh ./abc-file
server:./.parallel/tmp/aspire-1928520-1 );ssh server -- exec perl -e
\''@GNU_Parallel=("use","IPC::Open3;","use","MIME::Base64");
eval"@GNU_Parallel";my$eval=decode_base64(join"",@ARGV);eval$eval;'\'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=;
_EXIT_status=$?; mkdir -p ./.; rsync --protocol 30 --rsync-path=cd\
./.parallel/tmp/aspire-1928520-1/./.\;\ rsync -rlDzR -essh
server:./abc-file.out ./.;ssh server -- \(rm\ -f\
./.parallel/tmp/aspire-1928520-1/abc-file\;\ sh\ -c\ \'rmdir\
./.parallel/tmp/aspire-1928520-1/\ ./.parallel/tmp/\ ./.parallel/\
2\>/dev/null\'\;rm\ -rf\ ./.parallel/tmp/aspire-1928520-1\;\);ssh
server -- \(rm\ -f\ ./.parallel/tmp/aspire-1928520-1/abc-file.out\;\
sh\ -c\ \'rmdir\ ./.parallel/tmp/aspire-1928520-1/\ ./.parallel/tmp/\
./.parallel/\ 2\>/dev/null\'\;rm\ -rf\
./.parallel/tmp/aspire-1928520-1\;\);ssh server -- rm -rf
.parallel/tmp/aspire-1928520-1; exit $_EXIT_status;
@end verbatim
@node Saving output to shell variables (advanced)
@chapter Saving output to shell variables (advanced)
GNU @strong{parset} will set shell variables to the output of GNU
@strong{parallel}. GNU @strong{parset} has one important limitation: It cannot be
part of a pipe. In particular this means it cannot read anything from
standard input (stdin) or pipe output to another program.
To use GNU @strong{parset} prepend command with destination variables:
@verbatim
parset myvar1,myvar2 echo ::: a b
echo $myvar1
echo $myvar2
@end verbatim
Output:
@verbatim
a
b
@end verbatim
If you only give a single variable, it will be treated as an array:
@verbatim
parset myarray seq {} 5 ::: 1 2 3
echo "${myarray[1]}"
@end verbatim
Output:
@verbatim
2
3
4
5
@end verbatim
The commands to run can be an array:
@verbatim
cmd=("echo '<<joe \"double space\" cartoon>>'" "pwd")
parset data ::: "${cmd[@]}"
echo "${data[0]}"
echo "${data[1]}"
@end verbatim
Output:
@verbatim
<<joe "double space" cartoon>>
[current dir]
@end verbatim
@node Saving to an SQL base (advanced)
@chapter Saving to an SQL base (advanced)
GNU @strong{parallel} can save into an SQL base. Point GNU @strong{parallel} to a
table and it will put the joblog there together with the variables and
the output each in their own column.
@menu
* CSV as SQL base::
* DBURL as table::
* Using multiple workers::
@end menu
@node CSV as SQL base
@section CSV as SQL base
The simplest is to use a CSV file as the storage table:
@verbatim
parallel --sqlandworker csv:///%2Ftmp/log.csv \
seq ::: 10 ::: 12 13 14
cat /tmp/log.csv
@end verbatim
Note how '/' in the path must be written as %2F.
Output will be similar to:
@verbatim
Seq,Host,Starttime,JobRuntime,Send,Receive,Exitval,_Signal,
Command,V1,V2,Stdout,Stderr
1,:,1458254498.254,0.069,0,9,0,0,"seq 10 12",10,12,"10
11
12
",
2,:,1458254498.278,0.080,0,12,0,0,"seq 10 13",10,13,"10
11
12
13
",
3,:,1458254498.301,0.083,0,15,0,0,"seq 10 14",10,14,"10
11
12
13
14
",
@end verbatim
A proper CSV reader (like LibreOffice or R's read.csv) will read this
format correctly - even with fields containing newlines as above.
If the output is big you may want to put it into files using @strong{--results}:
@verbatim
parallel --results outdir --sqlandworker csv:///%2Ftmp/log2.csv \
seq ::: 10 ::: 12 13 14
cat /tmp/log2.csv
@end verbatim
Output will be similar to:
@verbatim
Seq,Host,Starttime,JobRuntime,Send,Receive,Exitval,_Signal,
Command,V1,V2,Stdout,Stderr
1,:,1458824738.287,0.029,0,9,0,0,
"seq 10 12",10,12,outdir/1/10/2/12/stdout,outdir/1/10/2/12/stderr
2,:,1458824738.298,0.025,0,12,0,0,
"seq 10 13",10,13,outdir/1/10/2/13/stdout,outdir/1/10/2/13/stderr
3,:,1458824738.309,0.026,0,15,0,0,
"seq 10 14",10,14,outdir/1/10/2/14/stdout,outdir/1/10/2/14/stderr
@end verbatim
@node DBURL as table
@section DBURL as table
The CSV file is an example of a DBURL.
GNU @strong{parallel} uses a DBURL to address the table. A DBURL has this format:
@verbatim
vendor://[[user][:password]@][host][:port]/[database[/table]
@end verbatim
Example:
@verbatim
mysql://scott:tiger@my.example.com/mydatabase/mytable
postgresql://scott:tiger@pg.example.com/mydatabase/mytable
sqlite3:///%2Ftmp%2Fmydatabase/mytable
csv:///%2Ftmp/log.csv
@end verbatim
To refer to @strong{/tmp/mydatabase} with @strong{sqlite} or @strong{csv} you need to
encode the @strong{/} as @strong{%2F}.
Run a job using @strong{sqlite} on @strong{mytable} in @strong{/tmp/mydatabase}:
@verbatim
DBURL=sqlite3:///%2Ftmp%2Fmydatabase
DBURLTABLE=$DBURL/mytable
parallel --sqlandworker $DBURLTABLE echo ::: foo bar ::: baz quuz
@end verbatim
To see the result:
@verbatim
sql $DBURL 'SELECT * FROM mytable ORDER BY Seq;'
@end verbatim
Output will be similar to:
@verbatim
Seq|Host|Starttime|JobRuntime|Send|Receive|Exitval|_Signal|
Command|V1|V2|Stdout|Stderr
1|:|1451619638.903|0.806||8|0|0|echo foo baz|foo|baz|foo baz
|
2|:|1451619639.265|1.54||9|0|0|echo foo quuz|foo|quuz|foo quuz
|
3|:|1451619640.378|1.43||8|0|0|echo bar baz|bar|baz|bar baz
|
4|:|1451619641.473|0.958||9|0|0|echo bar quuz|bar|quuz|bar quuz
|
@end verbatim
The first columns are well known from @strong{--joblog}. @strong{V1} and @strong{V2} are
data from the input sources. @strong{Stdout} and @strong{Stderr} are standard
output and standard error, respectively.
@node Using multiple workers
@section Using multiple workers
Using an SQL base as storage costs overhead in the order of 1 second
per job.
One of the situations where it makes sense is if you have multiple
workers.
You can then have a single master machine that submits jobs to the SQL
base (but does not do any of the work):
@verbatim
parallel --sqlmaster $DBURLTABLE echo ::: foo bar ::: baz quuz
@end verbatim
On the worker machines you run exactly the same command except you
replace @strong{--sqlmaster} with @strong{--sqlworker}.
@verbatim
parallel --sqlworker $DBURLTABLE echo ::: foo bar ::: baz quuz
@end verbatim
To run a master and a worker on the same machine use @strong{--sqlandworker}
as shown earlier.
@node --pipe
@chapter --pipe
The @strong{--pipe} functionality puts GNU @strong{parallel} in a different mode:
Instead of treating the data on stdin (standard input) as arguments
for a command to run, the data will be sent to stdin (standard input)
of the command.
The typical situation is:
@verbatim
command_A | command_B | command_C
@end verbatim
where command_B is slow, and you want to speed up command_B.
@menu
* Chunk size::
* Records::
* Fixed length records::
* Record separators::
* Header::
* --pipepart::
@end menu
@node Chunk size
@section Chunk size
By default GNU @strong{parallel} will start an instance of command_B, read a
chunk of 1 MB, and pass that to the instance. Then start another
instance, read another chunk, and pass that to the second instance.
@verbatim
cat num1000000 | parallel --pipe wc
@end verbatim
Output (the order may be different):
@verbatim
165668 165668 1048571
149797 149797 1048579
149796 149796 1048572
149797 149797 1048579
149797 149797 1048579
149796 149796 1048572
85349 85349 597444
@end verbatim
The size of the chunk is not exactly 1 MB because GNU @strong{parallel} only
passes full lines - never half a line, thus the blocksize is only
1 MB on average. You can change the block size to 2 MB with @strong{--block}:
@verbatim
cat num1000000 | parallel --pipe --block 2M wc
@end verbatim
Output (the order may be different):
@verbatim
315465 315465 2097150
299593 299593 2097151
299593 299593 2097151
85349 85349 597444
@end verbatim
GNU @strong{parallel} treats each line as a record. If the order of records
is unimportant (e.g. you need all lines processed, but you do not care
which is processed first), then you can use @strong{--roundrobin}. Without
@strong{--roundrobin} GNU @strong{parallel} will start a command per block; with
@strong{--roundrobin} only the requested number of jobs will be started
(@strong{--jobs}). The records will then be distributed between the running
jobs:
@verbatim
cat num1000000 | parallel --pipe -j4 --roundrobin wc
@end verbatim
Output will be similar to:
@verbatim
149797 149797 1048579
299593 299593 2097151
315465 315465 2097150
235145 235145 1646016
@end verbatim
One of the 4 instances got a single record, 2 instances got 2 full
records each, and one instance got 1 full and 1 partial record.
@node Records
@section Records
GNU @strong{parallel} sees the input as records. The default record is a single
line.
Using @strong{-N140000} GNU @strong{parallel} will read 140000 records at a time:
@verbatim
cat num1000000 | parallel --pipe -N140000 wc
@end verbatim
Output (the order may be different):
@verbatim
140000 140000 868895
140000 140000 980000
140000 140000 980000
140000 140000 980000
140000 140000 980000
140000 140000 980000
140000 140000 980000
20000 20000 140001
@end verbatim
Note how that the last job could not get the full 140000 lines, but
only 20000 lines.
If a record is 75 lines @strong{-L} can be used:
@verbatim
cat num1000000 | parallel --pipe -L75 wc
@end verbatim
Output (the order may be different):
@verbatim
165600 165600 1048095
149850 149850 1048950
149775 149775 1048425
149775 149775 1048425
149850 149850 1048950
149775 149775 1048425
85350 85350 597450
25 25 176
@end verbatim
Note how GNU @strong{parallel} still reads a block of around 1 MB; but
instead of passing full lines to @strong{wc} it passes full 75 lines at a
time. This of course does not hold for the last job (which in this
case got 25 lines).
@node Fixed length records
@section Fixed length records
Fixed length records can be processed by setting @strong{--recend ''} and
@strong{--block @emph{recordsize}}. A header of size @emph{n} can be processed with
@strong{--header .@{@emph{n}@}}.
Here is how to process a file with a 4-byte header and a 3-byte record
size:
@verbatim
cat fixedlen | parallel --pipe --header .{4} --block 3 --recend '' \
'echo start; cat; echo'
@end verbatim
Output:
@verbatim
start
HHHHAAA
start
HHHHCCC
start
HHHHBBB
@end verbatim
It may be more efficient to increase @strong{--block} to a multiplum of the
record size.
@node Record separators
@section Record separators
GNU @strong{parallel} uses separators to determine where two records split.
@strong{--recstart} gives the string that starts a record; @strong{--recend} gives the
string that ends a record. The default is @strong{--recend '\n'} (newline).
If both @strong{--recend} and @strong{--recstart} are given, then the record will only
split if the recend string is immediately followed by the recstart
string.
Here the @strong{--recend} is set to @strong{', '}:
@verbatim
echo /foo, bar/, /baz, qux/, | \
parallel -kN1 --recend ', ' --pipe echo JOB{#}\;cat\;echo END
@end verbatim
Output:
@verbatim
JOB1
/foo, END
JOB2
bar/, END
JOB3
/baz, END
JOB4
qux/,
END
@end verbatim
Here the @strong{--recstart} is set to @strong{/}:
@verbatim
echo /foo, bar/, /baz, qux/, | \
parallel -kN1 --recstart / --pipe echo JOB{#}\;cat\;echo END
@end verbatim
Output:
@verbatim
JOB1
/foo, barEND
JOB2
/, END
JOB3
/baz, quxEND
JOB4
/,
END
@end verbatim
Here both @strong{--recend} and @strong{--recstart} are set:
@verbatim
echo /foo, bar/, /baz, qux/, | \
parallel -kN1 --recend ', ' --recstart / --pipe \
echo JOB{#}\;cat\;echo END
@end verbatim
Output:
@verbatim
JOB1
/foo, bar/, END
JOB2
/baz, qux/,
END
@end verbatim
Note the difference between setting one string and setting both strings.
With @strong{--regexp} the @strong{--recend} and @strong{--recstart} will be treated as
a regular expression:
@verbatim
echo foo,bar,_baz,__qux, | \
parallel -kN1 --regexp --recend ,_+ --pipe \
echo JOB{#}\;cat\;echo END
@end verbatim
Output:
@verbatim
JOB1
foo,bar,_END
JOB2
baz,__END
JOB3
qux,
END
@end verbatim
GNU @strong{parallel} can remove the record separators with
@strong{--remove-rec-sep}/@strong{--rrs}:
@verbatim
echo foo,bar,_baz,__qux, | \
parallel -kN1 --rrs --regexp --recend ,_+ --pipe \
echo JOB{#}\;cat\;echo END
@end verbatim
Output:
@verbatim
JOB1
foo,barEND
JOB2
bazEND
JOB3
qux,
END
@end verbatim
@node Header
@section Header
If the input data has a header, the header can be repeated for each
job by matching the header with @strong{--header}. If headers start with
@strong{%} you can do this:
@verbatim
cat num_%header | \
parallel --header '(%.*\n)*' --pipe -N3 echo JOB{#}\;cat
@end verbatim
Output (the order may be different):
@verbatim
JOB1
%head1
%head2
1
2
3
JOB2
%head1
%head2
4
5
6
JOB3
%head1
%head2
7
8
9
JOB4
%head1
%head2
10
@end verbatim
If the header is 2 lines, @strong{--header} 2 will work:
@verbatim
cat num_%header | parallel --header 2 --pipe -N3 echo JOB{#}\;cat
@end verbatim
Output: Same as above.
@node --pipepart
@section --pipepart
@strong{--pipe} is not very efficient. It maxes out at around 500
MB/s. @strong{--pipepart} can easily deliver 5 GB/s. But there are a few
limitations. The input has to be a normal file (not a pipe) given by
@strong{-a} or @strong{::::} and @strong{-L}/@strong{-l}/@strong{-N} do not work. @strong{--recend} and
@strong{--recstart}, however, @emph{do} work, and records can often be split on
that alone.
@verbatim
parallel --pipepart -a num1000000 --block 3m wc
@end verbatim
Output (the order may be different):
@verbatim
444443 444444 3000002
428572 428572 3000004
126985 126984 888890
@end verbatim
@node Shebang
@chapter Shebang
@menu
* Input data and parallel command in the same file::
* Parallelizing existing scripts::
@end menu
@node Input data and parallel command in the same file
@section Input data and parallel command in the same file
GNU @strong{parallel} is often called as this:
@verbatim
cat input_file | parallel command
@end verbatim
With @strong{--shebang} the @emph{input_file} and @strong{parallel} can be combined into the same script.
UNIX shell scripts start with a shebang line like this:
@verbatim
#!/bin/bash
@end verbatim
GNU @strong{parallel} can do that, too. With @strong{--shebang} the arguments can be
listed in the file. The @strong{parallel} command is the first line of the
script:
@verbatim
#!/usr/bin/parallel --shebang -r echo
foo
bar
baz
@end verbatim
Output (the order may be different):
@verbatim
foo
bar
baz
@end verbatim
@node Parallelizing existing scripts
@section Parallelizing existing scripts
GNU @strong{parallel} is often called as this:
@verbatim
cat input_file | parallel command
parallel command ::: foo bar
@end verbatim
If @strong{command} is a script, @strong{parallel} can be combined into a single
file so this will run the script in parallel:
@verbatim
cat input_file | command
command foo bar
@end verbatim
This @strong{perl} script @strong{perl_echo} works like @strong{echo}:
@verbatim
#!/usr/bin/perl
print "@ARGV\n"
@end verbatim
It can be called as this:
@verbatim
parallel perl_echo ::: foo bar
@end verbatim
By changing the @strong{#!}-line it can be run in parallel:
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/perl
print "@ARGV\n"
@end verbatim
Thus this will work:
@verbatim
perl_echo foo bar
@end verbatim
Output (the order may be different):
@verbatim
foo
bar
@end verbatim
This technique can be used for:
@table @asis
@item Perl:
@anchor{Perl:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/perl
print "Arguments @ARGV\n";
@end verbatim
@item Python:
@anchor{Python:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/python
import sys
print 'Arguments', str(sys.argv)
@end verbatim
@item Bash/sh/zsh/Korn shell:
@anchor{Bash/sh/zsh/Korn shell:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /bin/bash
echo Arguments "$@"
@end verbatim
@item csh:
@anchor{csh:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /bin/csh
echo Arguments "$argv"
@end verbatim
@item Tcl:
@anchor{Tcl:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/tclsh
puts "Arguments $argv"
@end verbatim
@item R:
@anchor{R:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/Rscript --vanilla --slave
args <- commandArgs(trailingOnly = TRUE)
print(paste("Arguments ",args))
@end verbatim
@item GNUplot:
@anchor{GNUplot:}
@verbatim
#!/usr/bin/parallel --shebang-wrap ARG={} /usr/bin/gnuplot
print "Arguments ", system('echo $ARG')
@end verbatim
@item Ruby:
@anchor{Ruby:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/ruby
print "Arguments "
puts ARGV
@end verbatim
@item Octave:
@anchor{Octave:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/octave
printf ("Arguments");
arg_list = argv ();
for i = 1:nargin
printf (" %s", arg_list{i});
endfor
printf ("\n");
@end verbatim
@item Common LISP:
@anchor{Common LISP:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/clisp
(format t "~&~S~&" 'Arguments)
(format t "~&~S~&" *args*)
@end verbatim
@item PHP:
@anchor{PHP:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/php
<?php
echo "Arguments";
foreach(array_slice($argv,1) as $v)
{
echo " $v";
}
echo "\n";
?>
@end verbatim
@item Node.js:
@anchor{Node.js:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/node
var myArgs = process.argv.slice(2);
console.log('Arguments ', myArgs);
@end verbatim
@item LUA:
@anchor{LUA:}
@verbatim
#!/usr/bin/parallel --shebang-wrap /usr/bin/lua
io.write "Arguments"
for a = 1, #arg do
io.write(" ")
io.write(arg[a])
end
print("")
@end verbatim
@item C#:
@anchor{C#:}
@verbatim
#!/usr/bin/parallel --shebang-wrap ARGV={} /usr/bin/csharp
var argv = Environment.GetEnvironmentVariable("ARGV");
print("Arguments "+argv);
@end verbatim
@end table
@node Semaphore
@chapter Semaphore
GNU @strong{parallel} can work as a counting semaphore. This is slower and less
efficient than its normal mode.
A counting semaphore is like a row of toilets. People needing a toilet
can use any toilet, but if there are more people than toilets, they
will have to wait for one of the toilets to become available.
An alias for @strong{parallel --semaphore} is @strong{sem}.
@strong{sem} will follow a person to the toilets, wait until a toilet is
available, leave the person in the toilet and exit.
@strong{sem --fg} will follow a person to the toilets, wait until a toilet is
available, stay with the person in the toilet and exit when the person
exits.
@strong{sem --wait} will wait for all persons to leave the toilets.
@strong{sem} does not have a queue discipline, so the next person is chosen
randomly.
@strong{-j} sets the number of toilets.
@menu
* Mutex::
* Counting semaphore::
* Timeout::
@end menu
@node Mutex
@section Mutex
The default is to have only one toilet (this is called a mutex). The
program is started in the background and @strong{sem} exits immediately. Use
@strong{--wait} to wait for all @strong{sem}s to finish:
@verbatim
sem 'sleep 1; echo The first finished' &&
echo The first is now running in the background &&
sem 'sleep 1; echo The second finished' &&
echo The second is now running in the background
sem --wait
@end verbatim
Output:
@verbatim
The first is now running in the background
The first finished
The second is now running in the background
The second finished
@end verbatim
The command can be run in the foreground with @strong{--fg}, which will only
exit when the command completes:
@verbatim
sem --fg 'sleep 1; echo The first finished' &&
echo The first finished running in the foreground &&
sem --fg 'sleep 1; echo The second finished' &&
echo The second finished running in the foreground
sem --wait
@end verbatim
The difference between this and just running the command, is that a
mutex is set, so if other @strong{sem}s were running in the background only one
would run at a time.
To control which semaphore is used, use
@strong{--semaphorename}/@strong{--id}. Run this in one terminal:
@verbatim
sem --id my_id -u 'echo First started; sleep 10; echo First done'
@end verbatim
and simultaneously this in another terminal:
@verbatim
sem --id my_id -u 'echo Second started; sleep 10; echo Second done'
@end verbatim
Note how the second will only be started when the first has finished.
@node Counting semaphore
@section Counting semaphore
A mutex is like having a single toilet: When it is in use everyone
else will have to wait. A counting semaphore is like having multiple
toilets: Several people can use the toilets, but when they all are in
use, everyone else will have to wait.
@strong{sem} can emulate a counting semaphore. Use @strong{--jobs} to set the
number of toilets like this:
@verbatim
sem --jobs 3 --id my_id -u 'echo Start 1; sleep 5; echo 1 done' &&
sem --jobs 3 --id my_id -u 'echo Start 2; sleep 6; echo 2 done' &&
sem --jobs 3 --id my_id -u 'echo Start 3; sleep 7; echo 3 done' &&
sem --jobs 3 --id my_id -u 'echo Start 4; sleep 8; echo 4 done' &&
sem --wait --id my_id
@end verbatim
Output:
@verbatim
Start 1
Start 2
Start 3
1 done
Start 4
2 done
3 done
4 done
@end verbatim
@node Timeout
@section Timeout
With @strong{--semaphoretimeout} you can force running the command anyway after
a period (positive number) or give up (negative number):
@verbatim
sem --id foo -u 'echo Slow started; sleep 5; echo Slow ended' &&
sem --id foo --semaphoretimeout 1 'echo Forced running after 1 sec' &&
sem --id foo --semaphoretimeout -2 'echo Give up after 2 secs'
sem --id foo --wait
@end verbatim
Output:
@verbatim
Slow started
parallel: Warning: Semaphore timed out. Stealing the semaphore.
Forced running after 1 sec
parallel: Warning: Semaphore timed out. Exiting.
Slow ended
@end verbatim
Note how the 'Give up' was not run.
@node Informational
@chapter Informational
GNU @strong{parallel} has some options to give short information about the
configuration.
@strong{--help} will print a summary of the most important options:
@verbatim
parallel --help
@end verbatim
Output:
@verbatim
Usage:
parallel [options] [command [arguments]] < list_of_arguments
parallel [options] [command [arguments]] (::: arguments|:::: argfile(s))...
cat ... | parallel --pipe [options] [command [arguments]]
-j n Run n jobs in parallel
-k Keep same order
-X Multiple arguments with context replace
--colsep regexp Split input on regexp for positional replacements
{} {.} {/} {/.} {#} {%} {= perl code =} Replacement strings
{3} {3.} {3/} {3/.} {=3 perl code =} Positional replacement strings
With --plus: {} = {+/}/{/} = {.}.{+.} = {+/}/{/.}.{+.} = {..}.{+..} =
{+/}/{/..}.{+..} = {...}.{+...} = {+/}/{/...}.{+...}
-S sshlogin Example: foo@server.example.com
--slf .. Use ~/.parallel/sshloginfile as the list of sshlogins
--trc {}.bar Shorthand for --transfer --return {}.bar --cleanup
--onall Run the given command with argument on all sshlogins
--nonall Run the given command with no arguments on all sshlogins
--pipe Split stdin (standard input) to multiple jobs.
--recend str Record end separator for --pipe.
--recstart str Record start separator for --pipe.
See 'man parallel' for details
Academic tradition requires you to cite works you base your article on.
When using programs that use GNU Parallel to process data for publication
please cite:
O. Tange (2011): GNU Parallel - The Command-Line Power Tool,
;login: The USENIX Magazine, February 2011:42-47.
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.
@end verbatim
When asking for help, always report the full output of this:
@verbatim
parallel --version
@end verbatim
Output:
@verbatim
GNU parallel 20230122
Copyright (C) 2007-2023 Ole Tange, http://ole.tange.dk and Free Software
Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
GNU parallel comes with no warranty.
Web site: https://www.gnu.org/software/parallel
When using programs that use GNU Parallel to process data for publication
please cite as described in 'parallel --citation'.
@end verbatim
In scripts @strong{--minversion} can be used to ensure the user has at least
this version:
@verbatim
parallel --minversion 20130722 && \
echo Your version is at least 20130722.
@end verbatim
Output:
@verbatim
20160322
Your version is at least 20130722.
@end verbatim
If you are using GNU @strong{parallel} for research the BibTeX citation can be
generated using @strong{--citation}:
@verbatim
parallel --citation
@end verbatim
Output:
@verbatim
Academic tradition requires you to cite works you base your article on.
When using programs that use GNU Parallel to process data for publication
please cite:
@article{Tange2011a,
title = {GNU Parallel - The Command-Line Power Tool},
author = {O. Tange},
address = {Frederiksberg, Denmark},
journal = {;login: The USENIX Magazine},
month = {Feb},
number = {1},
volume = {36},
url = {https://www.gnu.org/s/parallel},
year = {2011},
pages = {42-47},
doi = {10.5281/zenodo.16303}
}
(Feel free to use \nocite{Tange2011a})
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.
If you send a copy of your published article to tange@gnu.org, it will be
mentioned in the release notes of next version of GNU Parallel.
@end verbatim
With @strong{--max-line-length-allowed} GNU @strong{parallel} will report the maximal
size of the command line:
@verbatim
parallel --max-line-length-allowed
@end verbatim
Output (may vary on different systems):
@verbatim
131071
@end verbatim
@strong{--number-of-cpus} and @strong{--number-of-cores} run system specific code to
determine the number of CPUs and CPU cores on the system. On
unsupported platforms they will return 1:
@verbatim
parallel --number-of-cpus
parallel --number-of-cores
@end verbatim
Output (may vary on different systems):
@verbatim
4
64
@end verbatim
@node Profiles
@chapter Profiles
The defaults for GNU @strong{parallel} can be changed systemwide by putting the
command line options in @strong{/etc/parallel/config}. They can be changed for
a user by putting them in @strong{~/.parallel/config}.
Profiles work the same way, but have to be referred to with @strong{--profile}:
@verbatim
echo '--nice 17' > ~/.parallel/nicetimeout
echo '--timeout 300%' >> ~/.parallel/nicetimeout
parallel --profile nicetimeout echo ::: A B C
@end verbatim
Output:
@verbatim
A
B
C
@end verbatim
Profiles can be combined:
@verbatim
echo '-vv --dry-run' > ~/.parallel/dryverbose
parallel --profile dryverbose --profile nicetimeout echo ::: A B C
@end verbatim
Output:
@verbatim
echo A
echo B
echo C
@end verbatim
@node Spread the word
@chapter Spread the word
I hope you have learned something from this tutorial.
If you like GNU @strong{parallel}:
@itemize
@item (Re-)walk through the tutorial if you have not done so in the past year
(https://www.gnu.org/software/parallel/parallel_tutorial.html)
@item Give a demo at your local user group/your team/your colleagues
@item Post the intro videos and the tutorial on Reddit, Mastodon, Diaspora*,
forums, blogs, Identi.ca, Google+, Twitter, Facebook, Linkedin, and
mailing lists
@item Request or write a review for your favourite blog or magazine
(especially if you do something cool with GNU @strong{parallel})
@item Invite me for your next conference
@end itemize
If you use GNU @strong{parallel} for research:
@itemize
@item Please cite GNU @strong{parallel} in you publications (use @strong{--citation})
@end itemize
If GNU @strong{parallel} saves you money:
@itemize
@item (Have your company) donate to FSF or become a member
https://my.fsf.org/donate/
@end itemize
(C) 2013-2023 Ole Tange, GFDLv1.3+ (See
LICENSES/GFDL-1.3-or-later.txt)
@bye
|