Issue 30488: Documentation for subprocess.STDOUT needs clarification

➜

This issue tracker has been migrated to GitHub, and is currently read-only.
For more information, see the GitHub FAQs in the Python's Developer Guide.

This issue has been migrated to GitHub: https://github.com/python/cpython/issues/74673

classification

Title:	Documentation for subprocess.STDOUT needs clarification
Type:	behavior	Stage:	resolved
Components:	Interpreter Core	Versions:	Python 3.7, Python 3.6, Python 3.3, Python 3.4, Python 3.5, Python 2.7

process

Status:	closed	Resolution:	duplicate
Dependencies:		Superseder:	subprocess.Popen(stderr=STDOUT) fails to redirect subprocess stderr to stdout View: 22274
Assigned To:		Nosy List:	max
Priority:	normal	Keywords:

Created on 2017-05-26 17:42 by max, last changed 2022-04-11 14:58 by admin. This issue is now closed.

Messages (1)
msg294560 - (view)	Author: Max (max) *	Date: 2017-05-26 17:42
The documentation states that subprocess.STDOUT is: Special value that can be used as the stderr argument to Popen and indicates that standard error should go into the same handle as standard output. However, when Popen is called with stdout=None, stderr=subprocess.STDOUT, stderr is not redirected to stdout and continues to be sent to stderr. To reproduce the problem: $ python >/dev/null -c 'import subprocess;\ subprocess.call(["ls", "/404"],stderr=subprocess.STDOUT)' and observe the error message appearing on the console (assuming /404 directory does not exist). This was reported on SO 5 years ago: https://stackoverflow.com/questions/11495783/redirect-subprocess-stderr-to-stdout. The SO attributed this to a documentation issue, but arguably it should be considered a bug because there seems to be no reason to make subprocess.STDOUT unusable in this very common use case.

msg294560 - (view)

Author: Max (max) *

Date: 2017-05-26 17:42

The documentation states that subprocess.STDOUT is:

Special value that can be used as the stderr argument to Popen and indicates that standard error should go into the same handle as standard output.

However, when Popen is called with stdout=None, stderr=subprocess.STDOUT, stderr is not redirected to stdout and continues to be sent to stderr.

To reproduce the problem:

$ python >/dev/null -c 'import subprocess;\
                        subprocess.call(["ls", "/404"],stderr=subprocess.STDOUT)'

and observe the error message appearing on the console (assuming /404 directory does not exist).

This was reported on SO 5 years ago: https://stackoverflow.com/questions/11495783/redirect-subprocess-stderr-to-stdout.

The SO attributed this to a documentation issue, but arguably it should be considered a bug because there seems to be no reason to make subprocess.STDOUT unusable in this very common use case.

History
Date	User	Action	Args
2022-04-11 14:58:46	admin	set	github: 74673
2017-05-26 18:33:14	eryksun	set	status: open -> closed superseder: subprocess.Popen(stderr=STDOUT) fails to redirect subprocess stderr to stdout resolution: duplicate stage: resolved
2017-05-26 17:42:41	max	create