os.popen with os.close gives error message

[dtrosset]

BPO	1574310
Nosy	@ronaldoussoren, @devdanzin

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2009-05-12.17:05:12.405>
created_at = <Date 2006-10-10.07:45:08.000>
labels = ['invalid', 'type-bug', 'library']
title = 'os.popen with os.close gives error message'
updated_at = <Date 2009-05-12.17:05:12.404>
user = 'https://bugs.python.org/dtrosset'

bugs.python.org fields:

activity = <Date 2009-05-12.17:05:12.404>
actor = 'ajaksu2'
assignee = 'none'
closed = True
closed_date = <Date 2009-05-12.17:05:12.405>
closer = 'ajaksu2'
components = ['Library (Lib)']
creation = <Date 2006-10-10.07:45:08.000>
creator = 'dtrosset'
dependencies = []
files = []
hgrepos = []
issue_num = 1574310
keywords = []
message_count = 3.0
messages = ['61018', '61019', '84528']
nosy_count = 3.0
nosy_names = ['ronaldoussoren', 'ajaksu2', 'dtrosset']
pr_nums = []
priority = 'low'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue1574310'
versions = ['Python 2.6']

[dtrosset]

Given the following code:

  import os
  child_stdin = os.popen("cat -", "w")
  old_stdout = os.dup(1)
  os.close(child_stdin.fileno())
  print "foo"
  os.dup2(old_stdout, 1)
  os.close(old_stdout)

I got these different results depending on the version
of python I am using.

$ python2.4 -V 
Python 2.4.4c0
$ python2.4 test.py 
foo
close failed: [Errno 9] Bad file descriptor

$ python2.3 -V 
Python 2.3.5
$ python2.3 test/new/test.py 
foo

My .02$ guess is that underlying file descriptor of
child_stdin being closed, when trying to delete this
object, it tries again to close it.

[ronaldoussoren]

Logged In: YES
user_id=580910

IMHO this is "don't do that then" territory. You're poking around in the inside of file objects, you have to be careful if you do that.

BTW. What are you trying to accomplish? If you set sys.stdout to child_stdin (e.g. "import sys; sys.stdout = child_stdin"), print will write to the
pipe. If you really want to be sure that the C-level variable stdout writes to the pipe: os.dup2(child_stdout.fileno(), 1). You can then close
child_stdout, but still have to do the 'os.dup(1)' part if you want to restore the real stdout later on.

[devdanzin]

I'll close this based on Ronald's analysis unless opposition is voiced.