Re: feature request: "wait --free-slot" for poor man's parallelization

[Jan Schampera]

Mike Coleman wrote:
> Here's a bash feature I'd love to see, but don't have time to
> implement myself: a "--free-slot" flag to 'wait' that will wait until
> there is at least one free "slot" available, where a slot is basically
> a CPU core.
>
> Example usage:
>
> $ for ((n=0; n<100; n++)); do
>       my_experiment $n > $n.out &
>       wait --free-slot 4
>  done
>
> which I would run on a quad-CPU host.  The meaning of the wait is: if
> I already have four background invocations of "my_experiment" running,
> wait until one finishes, then proceed.  (If there are fewer than four
> running, proceed immediately.)
>
> This provides a nice sloppy way of letting me parallelize in a script
> without having to complicate things.  "make -j" and "xargs -P" provide
> some of this capability, but are a lot more work to set up--I'd really
> like to have this at my fingertips for interactive stuff.

I did something like that as a script, using an array of PIDs and a big 
loop and so on. I don't think it needs to be part of internal Bash 
features, it wasn't that much work.

J.