[Python-Dev] Portable "spawn" module for core?

[Guido van Rossum]

> Recently, Greg Ward <gward@cnri.reston.va.us> said:
> > BTW, is there anything like this on the Mac?  On what other OSs does it
> > even make sense to talk about programs spawning other programs?  (Surely
> > those GUI user interfaces have to do *something*...)
> 
> Yes, but the interface is quite a bit more high-level, so it's pretty
> difficult to reconcile with the Unix and Windows "every argument is a
> string" paradigm. You start the process and pass along an AppleEvent
> (basically an RPC-call) that will be presented to the program upon
> startup.
> 
> So on the mac there's a serious difference between (inventing the API
> interface here, cut down to make it understandable to non-macheads:-)
>   spawn("netscape", ("Open", "file.html"))
> and
>   spawn("netscape", ("OpenURL", "http://foo.com/file.html"))
> 
> The mac interface is (of course:-) infinitely more powerful, allowing
> you to talk to running apps, adressing stuff in it as COM/OLE does,
> etc. but unfortunately the simple case of spawn("rm", "-rf", "/") is
> impossible to represent in a meaningful way.
> 
> Add to that the fact that there's no stdin/stdout/stderr and there's
> little common ground. The one area of common ground is "run program X
> on files Y and Z and wait (or don't wait) for completion", so that is
> something that could maybe have a special method that could be
> implemented on all three mentioned platforms (and probably everything
> else as well). And even then it'll be surprising to Mac users that
> they have to _exit_ their editor (if you specify wait), not something
> people commonly do.

Indeed.  I'm guessing that Greg wrote his code specifically to drive
compilers, not so much to invoke an editor on a specific file.  It so
happens that the Windows compilers have command lines that look
sufficiently like the Unix compilers that this might actually work.

On the Mac, driving the compilers is best done using AppleEvents, so
it's probably better to to try to abuse the spawn() interface for
that...  (Greg, is there a higher level where the compiler actions are 
described without referring to specific programs, but perhaps just to
compiler actions and input and output files?)

--Guido van Rossum (home page: http://www.python.org/~guido/)