GNU parallel

GNU parallel is a command-line utility for Linux and other Unix-like operating systems which allows the user to execute shell scripts or commands in parallel. GNU parallel is free software, written by Ole Tange in Perl. It is available under the terms of GPLv3.

Usage


The most common usage is to replace the shell loop, for example to the form of where the file  contains arguments for   and where   may be empty.

Scripts using parallel are often easier to read than scripts using pexec.

The program parallel features also By default, parallel runs as many jobs in parallel as there are CPU cores.
 * 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 filenames containing special characters such as space, single quote, double quote, ampersand, and UTF-8 encoded characters;

Examples
The above is the parallel equivalent to:

This searches in all files in the current directory and its subdirectories whose name end in  for occurrences of the string. The parallel command will work as expected unless a file name contains a newline. In order to avoid this limitation one may use:

The above command uses the null character to delimit file names.

The above command expands  with as many arguments as the command line length permits, distributing them evenly among parallel jobs if required. This can lower process overhead for short-lived commands that take less time to finish than they do to launch.

The command above does the same as:

However, the former command which uses / /  is more resource efficient and will not halt with an error if the expansion of *.ogg is too large for the shell.