On Apr 7, 1:58 am, Nobody <nob...@nowhere.com> wrote: > On Wed, 06 Apr 2011 02:20:22 -0700, Pierre GM wrote: > > I need to run a third-party binary from a python script and retrieve > > its output (and its error messages). I use something like > >>>> process = subprocess.Popen(options, stdout=subprocess.PIPE, > > stderr=subprocess.PIPE) > >>>> (info_out, info_err) = process.communicate() > > That works fine, except that the third-party binary in question doesn't > > behave very nicely and tend to segfaults without returning any error. In > > that case, `process.communicate` hangs for ever. > > Odd. The .communicate method should return once both stdout and stderr > report EOF and the process is no longer running. Whether it terminates > normally or on a signal makes no difference. > > The only thing I can think of which would cause the situation which you > describe is if the child process spawns a child of its own before > terminating. In that case, stdout/stderr won't report EOF until any > processes which inherited them have terminated.
I think you nailed it. Running the incriminating command line in a terminal doesn't return to the prompt. In fact, a ps shows that the process is sleeping in the foreground. Guess I should change the subject of this thread... > > I thought about calling a `threading.Timer` that would call > > `process.terminate` if `process.wait` doesn't return after a given > > time... But it's not really a solution: the process in question can > > sometimes take a long time to run, and I wouldn't want to kill a > > process still running. > > I also thought about polling every x s and stopping when the result of > > a subprocess.Popen(["ps","-p",str(initialprocess.pid)], > > stdout=subprocess.PIPE) becomes only the header line, but my script > > needs to run on Windows as well (and no ps over there)... > > It should suffice to call .poll() on the process. In case that doesn't > work, the usual alternative would be to send signal 0 to the process (this > will fail with ESRCH if the process doesn't exist and do nothing > otherwise), e.g.: > > import os > import errno > > def exists(process): > try: > os.kill(process.pid, 0) > except OSError, e: > if e.errno == errno.ESRCH: > return False > raise > return True OK, gonna try that, thx. > You might need to take a different approach for Windows, but the above is > preferable to trying to parse "ps" output. Note that this only tells you > if /some/ process exists with the given PID, not whether the original > process exists; that information can only be obtained from the Popen > object. -- http://mail.python.org/mailman/listinfo/python-list
