On Sun, Jul 17, 2016 at 1:59 AM, Lawrence D’Oliveiro <lawrenced...@gmail.com> wrote: > The various subprocess functions > <https://docs.python.org/3/library/subprocess.html> have > arguments called “close_fds” and “pass_fds”, which specify which file > descriptors are to be > left open in the child process. Yet no matter what I set these to, it seemed > I could not pass > my pipes to a subprocess. > > What the docs *don’t* tell you is that these arguments do not control what > happens after the > exec. The file descriptors that are kept open are only those which do not > have the > FD_CLOEXEC flags set in their fcntl settings.
It works correctly in 3.4+, which makes the pass_fds file descriptors inheritable in the child, after fork. See issue 18571 and PEP 446, section "Other Changes": http://bugs.python.org/issue18571 https://www.python.org/dev/peps/pep-0446/#other-changes For example: Python 3.5.1+ (default, Mar 30 2016, 22:46:26) [GCC 5.3.1 20160330] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import os, subprocess >>> fdr, fdw = os.pipe() >>> fdw 4 >>> os.get_inheritable(fdw) False >>> subprocess.call(['python3'], pass_fds=[fdw]) child: Python 3.5.1+ (default, Mar 30 2016, 22:46:26) [GCC 5.3.1 20160330] on linux Type "help", "copyright", "credits" or "license" for more information. >>> import os >>> os.write(4, b'spam') 4 >>> exit() parent: 0 >>> os.read(fdr, 4) b'spam' -- https://mail.python.org/mailman/listinfo/python-list
