subprocess.run timeout does not function if shell=True and capture_output=True
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Description
Bug report
Bug description:
I am using python 3.12.4 on windows 10 and when calling subprocess.run("powershell", shell=True, capture_output=True, timeout=1) code execution seems to suspend indefinetly as the process now accepts the user input and interprets it.
This behaviour matches the one described in #81605 despite it having supposedly been fixed 5 years ago.
For example when calling subprocess.run("cmd", shell=True, capture_output=True, timeout=1) and then entering echo o>f.txt a new file called "f.txt" gets created with "o" as its content.
When using the IDLE Shell the process completes nearly instandly and returns this:
CompletedProcess(args='powershell', returncode=0, stdout=b'Windows PowerShell\r\nCopyright (C) Microsoft Corporation. Alle Rechte vorbehalten.\r\n\r\nLernen Sie das neue plattform\x81bergreifende PowerShell kennen - https://aka.ms/pscore6\r\n\r\nPS C:\Users\Mabeeck\Desktop\Python> ', stderr=b'')
The same applies for Python 3.8.9, 3.9.2, 3.10.6, 3.11.5 and 3.13.0b3
I'll apoligise in advance, if my impression of the bug beeing supposed to be fixed is wrong.
CPython versions tested on:
3.8, 3.9, 3.10, 3.11, 3.12, 3.13
Operating systems tested on:
Windows
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First steps
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Research direction
Start with the subprocess.run entry point using shell=True, capture_output=True, and timeout=1 on Windows, reproducing the reported powershell and cmd cases. Compare the behavior across the listed Python versions and determine what timeout behavior should occur when the child process accepts input; the issue is complete when the indefinite suspension is resolved and the behavior is covered by an appropriate regression test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- powershell, python, shell
- Domain
- operating-systems
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 35/100