Last week, I need to compress more than 20k png pictures in Shell. By use the optipng, it’s easy to do. There command in Shell like this:

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optipng *.png --dist ./dist

But I need to deal with more than 20k pictures, if I use the command above to compress pictures one by one, it’s too slow!

So I think, Is there anyway to use multiprocess to speed up?

The shell language seems not to provide APIs to deal with multiprocess programming.

After searching google, I find two ways to do this.

  • Open more than one Shell window, each one does the same things.
  • Using script language like python, create multiprocess then call the shell command in each process.

We know, in multiprocess programming or multi-threads programming, we need to avoid the race condition.

Such as, in this case, we need to avoid the optipng process not to deal with the same picture at the same time(And need to avoid a optipng process to deal with a picture which already compressed! ). Since the Shell lacks logic control, I think the second way is more appropriate.