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GNU Parallel is a shell tool for executing jobs in parallel using one or more computers. A job is can be a single command or a small script that has to be run for each of the lines in the input. The typical input is a list of files, a list of hosts, a list of users, a list of URLs, or a list of tables. A job can also be a command that reads from a pipe. GNU Parallel can then split the input and pipe it into commands in parallel.
If you use xargs and tee today you will find GNU Parallel very easy to use as GNU Parallel is written to have the same options as xargs. If you write loops in shell, you will find GNU Parallel may be able to replace most of the loops and make them run faster by running several jobs in parallel. GNU Parallel can even replace nested loops.
GNU Parallel makes sure output from the commands is the same output as you would get had you run the commands sequentially. This makes it possible to use output from GNU Parallel as input for other programs.
You can find more about GNU Parallel at: http://www.gnu.org/s/parallel/
You can install GNU Parallel in just 10 seconds with: (wget -O - pi.dk/3 || curl pi.dk/3/) | bash
Watch the intro video on http://www.youtube.com/playlist?list=PL284C9FF2488BC6D1
Walk through the tutorial (man parallel_tutorial). Your commandline will love you for it.
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.
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