New submission from Yoni Rozenshein <yoni...@gmail.com>:
In subprocess, the implementation of shell=True on Windows is to launch a
subprocess with using {comspec} /c "{args}" (normally comspec=cmd.exe).
By default, the output of cmd is encoded with the "active" codepage. In Python
3.6, you can decode this using encoding='oem'.
However, this actually loses information. For example, try creating a file with
a filename in a language that is not your active codepage, and then doing
subprocess.check_output('dir', shell=True). In the output, the filename is
replaced with question marks (not by Python, by cmd!).
To get the correct output, cmd has a "/u" switch (this switch has probably
existed forever - at least since Windows NT 4.0, by my internet search). The
output can then be decoded using encoding='utf-16-le', like any native Windows
string.
Currently, Popen constructs the command line in this hardcoded format:
{comspec} /c "{args}", so you can't get the /u in there with the shell=True
shortcut, and have to write your own wrapping code.
I suggest adding an feature to Popen where /u may be inserted before the /c
within the shell=True shortcut. I've thought of several ways to implement this:
1. A new argument to Popen, which indicates that we want Unicode shell output;
if True, add the /u. Note that we already have a couple of Windows-only
arguments to Popen, so this would not be a precedent.
2. If the encoding argument is 'utf-16-le' or one of its aliases, then add the
/u.
3. If the encoding argument is not None, then add the /u.
----------
components: Library (Lib)
messages: 318807
nosy: Yoni Rozenshein
priority: normal
severity: normal
status: open
title: [subprocess] Better Unicode support for shell=True on Windows
type: enhancement
versions: Python 3.6, Python 3.7, Python 3.8
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue33780>
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