mv change case of file extension causes: 'test.txt' and 'test.TXT' are the same file

[twatzl]

Hello,

I have the following issue

• Your Windows build number: Microsoft Windows [Version 10.0.17763.914]

• What you're doing and what's happening:

$~> cd /mnt/c/
$/mnt/c> mkdir tmp
$/mnt/c> cd tmp/
$/mnt/c/tmp> ls
$/mnt/c/tmp> touch test.txt
$/mnt/c/tmp> mv test.txt test.TXT
mv: 'test.txt' and 'test.TXT' are the same file

• What's wrong / what should be happening instead:

mv command cannot be used to rename file extension to upper case. I would expect similar behavior as in Windows Explorer or other tools that i can simply rename a file and change the case of the extension. I tested the same thing under Fedora and there it works without any issues.

[WSLUser]

I wanted to say this was correct behavior but I too tested on a Fedora cloud image and mv does indeed allow changing file extension case, not just file name. I think this a bug in mv personally, why would you have 2 identical files that only differ in case by file extension, NOT file name? I think there are a number of issues that can stem from that. I wouldn't change behavior for Windows and Linux should model Windows with this behavior.

[twatzl]

Well, the thing is that I some devices produce files with uppercase endings like .JPG, .PNG, etc. and some software uses lowercase endings by default and I wrote a bash script for renaming them all to uppercase, because that is what I need them to be (i don't care if upper or lower case, just consistent).

mv is used here for renaming and I don't have two files which are different in case, I just want to change the case of the file extension.

This works in Windows Explorer and on other operating systems so why should it not work in WSL?

I just tested again and it also works in ~ directory in WSL (OpenSuse), but not in /mnt/c

~> touch test.txt
~> mv test.txt test.TXT
~> mv test.TXT test.txt
~> cd /mnt/c/tmp/
/mnt/c/tmp> mv test.txt TEST.txt
mv: 'test.txt' and 'TEST.txt' are the same file

[WSLUser]

Ah ok, I see what you mean. Yes, just to make them all consistent (I personally prefer lowercase as it's easier to read to me) this should work. Do you have case sensitivity enabled in wsl.conf? If not, that would be why it's not working. You'd find the same issue exists for both WSL1 and WSL2.

[benhillis]

If you want DrvFs to behave case-sensitive you have to supply the case sensitive mount option:

https://devblogs.microsoft.com/commandline/improved-per-directory-case-sensitivity-support-in-wsl/

[therealkenc]

This one nominally asked and answered, caveat #3356 and #2937 (message) notwithstanding. The OP behavior is by-design by default.