subprocess: reading from stdout hangs process termination, waiting for ENTER keyboard signal

giohappy giohappy at gmail.com
Wed Apr 15 12:24:10 CEST 2009


On 15 Apr, 11:38, giohappy <gioha... at gmail.com> wrote:
> On 15 Apr, 11:20, Kushal Kumaran <kushal.kuma... at gmail.com> wrote:
>
>
>
> > On Wed, Apr 15, 2009 at 1:20 PM,giohappy<gioha... at gmail.com> wrote:
> > > On 14 Apr, 18:52, MRAB <goo... at mrabarnett.plus.com> wrote:
> > >> giohappywrote:
> > >> > Hello everyone.
> > >> > I'm trying to use subprocess module to launch a Windows console
> > >> > application. The application prints some results to standard output
> > >> > and then waits for the user to press any key to terminte. I can't
> > >> > control this behaviour, as the application is not mine...
> > >> > I'm stuck at the very first lines of my code. I'm trying to force
> > >> > process termination (even with proc.terminate()), and it works only if
> > >> > I don't read from stdout. If I do proc.stdout.read() the process
> > >> > hangs, and I have to manually press the keyboard to interrupt it.
> > >> > Probably it's due a low-level handle that is kept on the process
> > >> > stdout, waiting for the keypress event...
>
> > >> > How can I solve it?
> > >> > Giovanni
>
> > >> > ------- Code excerpt-------
>
> > >> > proc = subprocess.Popen('the_app.exe',
> > >> >                        shell=True,
> > >> >                        stdout=subprocess.PIPE,
> > >> >                        )
> > >> > #stdout_value = proc.communicate()[0]
> > >> > stdout_value = proc.stdout.read()
> > >> > PROCESS_TERMINATE = 1
> > >> > handle = win32api.OpenProcess(PROCESS_TERMINATE, False, proc.pid)
> > >> > win32api.TerminateProcess(handle, -1)
> > >> > win32api.CloseHandle(handle)
> > >> > print stdout_value
>
> > >> Try this:
>
> > >> proc = subprocess.Popen('the_app.exe',
> > >>                         shell=True,
> > >>                         stdin=subprocess.PIPE,
> > >>                         stdout=subprocess.PIPE,
> > >>                         )
> > >> stdout_value = proc.communicate("\n")[0]
>
> > > MRAB, I've tried that too but no result... I still have to press a
> > > keybord key to terminate (the classical "Press any key to continue")
>
> > If it actually is "Press any key to continue" rather than "Press Enter
> > to continue", it is likely directly using the console using available
> > low-level APIs, rather than reading from stdin.  AFAIK, subprocess
> > cannot handle that.
>
> > --
> > kushal
>
> If also tried with SendKeys [1], wich uses the windows.h keybd_event
> (), but it doesn't work... Ok, I leave this try, and look for a way to
> wrap the application in a bat file, hoping to succesfuly simulate the
> keypress event inside it.
>
> [1]http://www.rutherfurd.net/python/sendkeys/

Sorry, SendKeys is the solution. I was using it in the wronk place in
my script...



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