GNU parallel not working at all

Question

I have been trying to use GNU parallel for some time, but I have never been able to get it to function at all!

For example, running (in a non-empty directory!):

Answer 1

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.