python / python/cpython

subprocess.Popen doesn't properly escape < or > for windows batch files

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OS-windows stdlib topic-subprocess type-bug
Dominant language
Python
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Description

Bug report

Bug description:

subprocess.Popen doesn't properly escape < or > for windows batch files

example.bat

echo %*

example.py

import subprocess
from pathlib import Path

batch_file = Path().cwd() / 'example.bat'
subprocess.Popen([batch_file, 'arg1', 'arg2<99'])

Error

The system cannot find the file specified

Adding a space causes it to be correctly escaped:

subprocess.Popen([batch_file, 'arg1', 'arg2 <99'])
CPython versions tested on:

3.13

Operating systems tested on:

Windows

Linked PRs
  • gh-134544

Contributor guide

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the reported subprocess.Popen call in example.py and reproduce it on Windows with example.bat using the argument arg2<99, then compare it with the space-containing argument. Check the linked PR gh-134544 for the current state of the work; done means the no-space case is escaped correctly and the regression is covered.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
operating-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
25/100

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