GNU parallel
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| Developer(s) | GNU Project |
|---|---|
| Stable release | 20140322[1] / March 22, 2014 |
| Preview release | 20141022[2] / October 22, 2014 |
| Written in | Perl |
| Operating system | GNU |
| Type | Utility |
| License | GPLv3 |
| Website |
www |
GNU parallel is a command-line driven utility for Linux or other Unix-like operating systems which allows the user to execute shell scripts in parallel. GNU parallel is free software, written by Ole Tange in Perl. It is available under the terms of GPLv3.[3]
Usage
The most common usage is to replace the shell loop, for example
for x in `cat list` ; do do_something "$x" done | process_output
to the form of
cat list | parallel do_something | process_output
where the file list contains arguments for do_something and where process_output may be empty.
Scripts using parallel are often easier to read than scripts using pexec.
The program parallel features also
- grouping of standard output and standard error so the output of the parallel running jobs do not run together;
- retaining the order of output to remain the same order as input;
- dealing nicely with file names containing special characters such as space, single quote, double quote, ampersand, and UTF-8 encoded characters;
By default, parallel runs as many jobs in parallel as there are CPU cores.
An introduction video to GNU Parallel can be found on Wikimedia Commons.
Examples
find . -name "*.foo" | parallel grep bar
The above is the parallel equivalent to:
find . -name "*.foo" -exec grep bar {} +
This searches in all files in the current directory and its subdirectories whose name end in .foo for occurrences of the string bar. The parallel command will work as expected unless a file name contains a newline. In order to avoid this limitation one may use:
find . -name "*.foo" -print0 | parallel -0 grep bar
The above command uses the null character to delimit file names.
find . -name "*.foo" | parallel -X mv {} /tmp/trash
The above command uses {} to tell parallel to replace {} with the argument list.
find . -maxdepth 1 -type f -name "*.ogg" | parallel -X -r cp -v -p {} /home/media
The command above does the same as:
cp -v -p *.ogg /home/media
however, the former command which uses find/parallel/cp is more resource efficient and will not halt with an error if the expansion of *.ogg is too large for the shell.
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Wikimedia Commons has media related to GNU parallel. |
See also
References
- ↑ "GNU Parallel". directory.fsf.org. FSF. 22 March 2014. Retrieved 2 November 2014.
- ↑ "GNU Project Archives". ftp.gnu.org. GNU Project. 22 October 2014. Retrieved 2 November 2014.
- ↑ "GNU Parallel". GNU.org.
External links
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