Bugs item #1727024, was opened at 2007-05-28 17:41 Message generated for change (Comment added) made by ohuiginn You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1727024&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Documentation Group: Python 2.5 Status: Open Resolution: None Priority: 5 Private: No Submitted By: Dan O'Huiginn (ohuiginn) Assigned to: Nobody/Anonymous (nobody) Summary: subprocess: unreliability of returncode not clear from docs Initial Comment: The docs for the subprocess module (http://docs.python.org/lib/node533.html) give the impression that you can reliably find the return code of a process by checking returncode: -------- returncode The child return code. A None value indicates that the process hasn't terminated yet. A negative value -N indicates that the child was terminated by signal N (Unix only). -------- But in fact, returncode is only updated when the poll() method is called, and therefore will often be out-of-date. For instance >>> process=subprocess.Popen('true') #*nix command to do nothing >>> process.returncode >>> process.returncode==None True >>> process.poll() 0 >>> process.returncode 0 As far as I can see, it is always better to use poll() to check the status or return code of a subprocess. It might be good to either remove returncode from the docs entirely, or at least to explain that it won't always be correct. [incidentally, having returncode/poll() give None for a running process, and 0 for a process that has exited successfully, seems like a recipe for generating bugs. But I guess it's too late to do anything about that now] ---------------------------------------------------------------------- >Comment By: Dan O'Huiginn (ohuiginn) Date: 2007-06-06 18:41 Message: Logged In: YES user_id=1803299 Originator: YES Thanks for the reply, Collin. Perhaps something like: Note: The value stored in returncode may be out-of-date. Use poll() to reliably find the current return code. Alternatively, would it be possible to leave it out completely [and move the explanation of what return codes mean up into the description of poll()]? I can´t imagine many situations where it is a good idea to check returncode directly, and as I understand it the module documentation only covers variables that are useful to the outside world. ---------------------------------------------------------------------- Comment By: Collin Winter (collinwinter) Date: 2007-06-06 16:20 Message: Logged In: YES user_id=1344176 Originator: NO What wording would you rather see in the subprocess docs? ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1727024&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
