Windows support?

[hmaarrfk]

Any possibility of this working with windows?

it seems the two commands are the only ones that are windows specific, but I could be wrong

flags = fcntl(pipe_out, F_GETFL)
fcntl(pipe_out, F_SETFL, flags|os.O_NONBLOCK)

[minrk]

I'm not opposed to Windows support, but I have no idea how to do it. I thought all of the dup2, pipe stuff didn't work on Windows, but looking at the Python docs, they may, so it could be relatively easy. If you'd like to explore adding Windows support, that would be great!

[chrisjbillington]

You might be interested in some code of mine that does a similar thing and works on Windows, to see how this might be done. I'm not totally happy with it, since there is the possibility of C output coming out in the wrong order compared to Python output, but it mostly works.

It's difficult to do it in a foolproof way because Windows doesn't support select(), so you have to have separate threads reading the pipes for each stream, leading to a higher probability of stdout and stderr coming out in the wrong order depending on thread scheduling. A similar problem exists when using select() as far as I can tell (multiple writes to stdout could be read in one go even though there should be a line of stderr in between), but had a lower probability of actually resulting in wrong output. I'm yet to know of a way to do output redirection in a way that can distinguish between stdout and stderr without there being some race conditions like this leading to potentially wrong output order. But if it's just for humans looking at output then it's mostly good enough.

[jakirkham]

Do you have a permalink for that @chrisjbillington? Appears the location referenced has moved.

[chrisjbillington]

@jakirkham, I don't have a permalink to a line number, but the functionality is in the OutputInterceptor and StreamProxy classes in process_tree.py of the zprocess project.

[Lothiraldan]

Does the usage now of selector2 opens up the support of Windows?

[jakirkham]

Did you try it?

[minrk]

this gist appears to work on Windows with a similar approach, so it might not be so hard.

[chrisjbillington]

For what it's worth as another reference, the project of mine that does this on Windows is still around, has moved to GitHub:

https://github.com/chrisjbillington/zprocess/blob/89b464c3a2d10cb3282bea625670f807430adf03/zprocess/process_tree.py#L660