I am now able to print stderr to the screen, however I still can not run conditional statements against stderr.
Please see the screenshots(SS) here... https://www.dropbox.com/sh/31wyjtvqymo94uk/AAAZaxwB27nw1nmz7tz69I5La?dl=0 Bo > On Aug 28, 2014, at 6:12 PM, Cameron Simpson <c...@zip.com.au> wrote: > >> On 28Aug2014 09:42, Crush <crushe...@gmail.com> wrote: >> As far as the pipe in... >> >> "avconv -v verbose -re -analyzeduration 1000 >> -ihttp://localhost:6498/ms2/1382097438004/0MediaPlayer+0+/octoshape+hVV+octolive.americaone.com+V+aone+V+live+V+ONECONNXTDEMO1_HD_flv/aoneliveONECONNXTDEMO1HDflv >> -c:v rawvideo -c:a pcm_s16le -ar 48000 -f nut - | ./bmdplay -m 12 -f pipe:0" >> >> ...it has to be there. > > Indeed. We're not arguing about that. Leave it there for. > >> Currently, i am running a shell script that is handling this decoding >> process i.e. the real long avconv/bmdplay command. So you are saying leave >> the shell script and invoke it from a python script...something like "p = >> subprocess.Popen("./my_script.sh")? How will the above allow me to interact >> with stderr in oppose to running the avconv/bmdplay command directly in >> python? > > No, we're no saying that. > > You could (and presumably do) have this long incantation in your shell > script. As far as the Python stuff goes, that does not change anything: you > can invoke your shell script or invoke your long command directly. Either way > you need to grab the stderr on the fly and work with it. > > Personally, I would keep the pipeline in the shell script where it is easier > to edit and invoke the script from Python (easier to read). Your call. > >> As far as not using "shell=True," if I dont have it set to True, the >> terminal hangs and will not display stderr to the screen as it is currently >> does. > > Let's tackle shell=True later. > > What you need to do is examine stderr before the shell script/pipeline is > complete, and for that you need to separate starting the process, reading > stderr, and waiting for process completion into distinct parts, which was > what my example code was doing. I'll recite it again here: > > from subprocess import Popen, PIPE > > P = Popen("avconv ... lots of arguments...", shell=True, stderr=PIPE) > > for line in P.stderr: > ... examine the line from stderr ... > > # ok, we have read all of stderr now > xit = P.wait() > if xit != 0: > ... command was unsuccessful, complain, maybe abort ... > > Please try adapting your Python code to that and see where you end up. > Put a print statement as the first line in the for-loop so you can see if you > are receiving stderr lines as intended. > > Cheers, > Cameron Simpson <c...@zip.com.au> > > As soon as we started programming, we found to our surprise that it wasn't as > easy to get programs right as we had thought. Debugging had to be discovered. > I can remember the exact instant when I realized that a large part of my life > from then on was going to be spent in finding mistakes in my own programs. > - Maurice Wilkes discovers debugging, 1949
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