So I'm trying to monitor a shell process (think, 'tail -f some.log') inside
a Python program with a running a asyncio event loop (all defaults). If I
write my own (complicated) "spawn_process()" method that uses pty.fork() I
can do this:
loop = asyncio.get_event_loop()
fd = spawn_process(['/bin/sh', '-c', '/path/to/some/program'])
loop.add_reader(fd, print_output, fd) # print_output() does exactly that
loop.run_forever()
...and it works OK but it feels wrong since folks went to the trouble of
creating asyncio.create_subprocess_shell(). Assuming I write a function
that just spawns a subprocess and returns the resulting object:
@asyncio.coroutine
def subprocess_shell(cmd, **kwds):
proc = yield from asyncio.create_subprocess_shell(cmd, **kwds)
return proc
How do I get the fileno() of 'proc.stdout' so I can pass it to
loop.add_reader()? I can't seem to find it anywhere in the object. Maybe
I'm just not looking in the right place? I just want it to call a callback
when the stdout/stderr of the process has output. You can't use
loop.add_reader() without a file descriptor... Or perhaps I'm missing
something. Is there a "better way" to handle this kind of thing?
If I did the same thing with subprocess.Popen() the resulting proc.stdout
and proc.stderr will have fileno() methods that can be passed to
loop.add_reader(). I assume there was a good reason why the same
functionality was not added to asyncio.create_subprocess_shell()?
