On Jan 6, 10:30 am, Nobody <nob...@nowhere.com> wrote: > I think that you should close prog1.stdout here. Otherwise, there will > be two readers on the pipe (the calling process and prog2). Even if one of > them dies, there's always the possibility that the caller might eventually > decide to read prog1.stdout itself. If you close it in the caller, when > prog2 terminates there will be no readers, and prog1 will get SIGPIPE (or > write() will fail with EPIPE if SIGPIPE is handled).
Thanks for raising a great point, that prog1.stdout is also readable by the calling process, not just by prog2. Therefore, I agree it makes sense to explicitly call prog1.stdout.close() in the given code (say right after the creation of prog2). Suppose now all the prog1.poll() calls/loop are replaced by a single prog1.wait(). Without the explicit prog1.stdout.close(), prog1.wait() will not return, so the calling process still hangs. Because calling prog1.wait() means that the calling process will naturally never read prog1.stdout, I would argue that prog1.wait() should close the pipe before actually waiting for prog1 to exit. Makes sense? -- http://mail.python.org/mailman/listinfo/python-list
