calling `echo "test"` in python subproces gives `b'\\test"\n'`

Question

Why is it that in Python (3.6 in a Cygwin terminal running bash, on Windows 10)

>>> import subprocess
>>> subprocess.check_output(['echo', '"test"'])
b'\\test"\n'

NOTE: THE CONFUSING BIT IS THE LEADING BACKSLASH

To make that more clear:

>>> print(subprocess.check_output(['echo', '"test"']).decode())
\test"

Turns out Python2.7 gives me the expected result, but two different Python 3 installations give the wrong one.

In my understanding, subprocess.list2cmdline(x) should give something that is exactly equivalent when pasted in a terminal as subprocess.check_output(x). In this case though subprocess.list2cmdline(['echo', '"test"'])==r'echo \"test\"' and when pasting the latter into the terminal I do get the expected result

$ echo \"test\"
"test"

More tests:

>>> subprocess.check_output(subprocess.list2cmdline(['echo', '"test"']))
b'\\test"\n'

but

>>> subprocess.check_output(['echo', '"test"'], shell=True)
b'\\"test\\"\r\n'
>>> subprocess.check_output(subprocess.list2cmdline(['echo', '"test"']), shell=True)
b'\\"test\\"\r\n'

What is your question, exactly? How to convert the returned bytes-string to `str`? — DeepSpace, Feb 24 '21 at 18:55
are you confusing with `subprocess.run(['echo', '"test"'])` ? — matzeri, Feb 24 '21 at 18:56
The output should be `b'"test"\n'` for the first command shown, and that's normal: you are seeing the Python *representation* of the string captured by `subprocess`, not just the bytes in the string itself. — chepner, Feb 24 '21 at 18:57
@DeepSpace see the updated question. The output starts with a backslash after proper decoding and unescaping — Bananach, Feb 24 '21 at 19:19
@matzeri see the updated question. The output starts with a backslash after proper decoding and unescaping — Bananach, Feb 24 '21 at 19:19
@chepner see the updated question. The output starts with a backslash after proper decoding and unescaping — Bananach, Feb 24 '21 at 19:19
I cannot reproduce your claimed output: `subprocess.check_output(['echo', '"test"'])` produces the `bytes` value `b'"test"\n'`. — chepner, Feb 24 '21 at 19:25
No, but I can't even imagine a scenario where the environment affects the code like this. — chepner, Feb 25 '21 at 01:46

calling `echo "test"` in python subproces gives `b'\\test"\n'`

0 Answers0