GNU parallel not working at all

Depending on your operating system, you should check whether you're actually running the GNU version.

$ parallel --version
parallel: invalid option -- '-'
parallel [OPTIONS] command -- arguments
    for each argument, run command with argument, in parallel
parallel [OPTIONS] -- commands
    run specified commands in parallel

If this is the case, you're not running the GNU version. Ubuntu 12.04 is like this, and you'll need to manually install GNU parallel to get the functionality you expect.

Had issues running parallel as an external command from FREEMAT (MATLAB lookalike); the argumentFile was not fed to the command properly solved it by:

• Adding --gnu to options
• Not using cmdString syntax involving ["]

Code:

cmdString = 'parallel --gnu command ::: ';
    while j<=jLength
        cmdString = [cmdString argumentFilePath(j,:) ' '];
        j=j+1;
    end
    system(cmdString)

Thank you for that :) Im on Ubuntu 12.04 as well.

As I was about to complete writing this question, I ran parallel --version to report the version, only to find:

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

It is not clear to me why that flag is set by default. Needless to say, using --gnu worked!

Thought I would post this to save someone hours of frustration and confusion.

EDIT: To fix this permanently (in Ubuntu at least), delete the --tollef flag in /etc/parallel/config