Like the subject says, can you tell if the command line version fails in any programatical way? If not it would be great if it returned 0 or 1, or anything like that. So that you could do something like this (obviously not a great example but I hope you get my point )
It does return -1 on error, anything that aborts the whole program flow anyway. If the input set can only partially processed that's not a cause for aborting the whole thing.