Technology Tales

Adventures & experiences in contemporary technology

Restoring GNU Parallel Functionality in Ubuntu GNOME 13.04

31st July 2013

There is a handy comand line utility called GNU Parallel that allows you to run Linux commands on more than one CPU core at a time to perform parallel processing of the task at hand. Here is a form of the command that is similar to one that I often use:

ls *.* | parallel gm convert -sharpen 1×3 {} sharpened_images/{}

What it does is pipe a list of files in a folder to GraphicsMagick for sharpening and outputting to a sharpened_images directory. The {} in the command is where the filenames go in the sharpening command.

This worked fine in Ubuntu GNOME 12.10 but stopped doing so after I upgraded to the next version. A look on the web set me to running the following command:

parallel --version

That produced output that included the following line:

WARNING: YOU ARE USING --tollef. IF THINGS ARE ACTING WEIRD USE --gnu.

Rerunning the original command with the --gnu option worked but there was a more permanent solution than using something like this:

ls *.* | parallel --gnu gm convert -sharpen 1×3 {} sharpened_images/{}

That was editing /etc/parallel/config with root privileges to delete the --tollef option from there. With that completed, all was as it should again and it makes me wonder why the change was made in the first place. Perhaps because of it, there even is a discussion about the possibility of removing the --tollef option altogether since it is raising more questions than it answers.

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