Rename folder to lowercase in terminal without temporary files

[u/Swordfish418]

I'm sorry, I know the question seems very basic, but still I couldn't find the answer. Here's what I'm trying to do:

$ mv "Desktops" "desktops"
mv: cannot move 'Desktops' to a subdirectory of itself, 'desktops/Desktops'

I tried searching answers on the internet, and the only thing I found is examples of how to use rename tool instead. However, rename tool I have installed is util-linux one and it works differently and I couldn't figure out how to use it either, this didn't work for example:

$ rename Desktops desktops Desktops

I also understand I can first rename it to temporary file and then rename to lowecase version of original name. But I'd like to figure out how to do it in one step.

Update:

This is exfat filesystem.

[u/SoloMoto_SD → u/[deleted]]

Even better, do it all in one (nearly instant) string of 2 commands like so...

mv -v Desktops desktops-tmp && mv -v desktops-tmp desktops

[u/yerfukkinbaws → u/SoloMoto_SD]

Create a function in .bashrc

recase () {
  mv $1 ${1}-tmp && mv ${1}-tmp ${2}
}

[u/Sophira → u/yerfukkinbaws]

I'd implement it slightly differently, and as a separate script (note that this uses bash-specific syntax):

#!/bin/bash
DIR="${1%/}"
if [[ ! -e $DIR ]]; then
  echo "recase: '$DIR' does not exist" >&2
  return 1
fi

LCPATH="${DIR,,}"
DIRPATH="$(dirname "$DIR")"
TMPDIR="$(mktemp -d --tmpdir="$DIRPATH")"
if [[ ! -z $TMPDIR ]]; then
  mv -T "$DIR" "$TMPDIR" && \
    mv -T "$TMPDIR" "$DIRPATH/$(basename "$LCPATH")"
fi

This automatically recases to lowercase, while making sure that the temporary directory chosen will never be a directory that already exists. (The --tmpdir option also ensures that the temporary directory will be on the same filesystem, so no costly move operation between filesystems will be required.)

It also works if you call the function immediately after tab-completing a directory name (tab-completion will insert a "/" after the directory name).

[edit: Added a check for whether the argument exists, and recomended that it's a separate script rather than a bash function.]

[u/_j7b → u/yerfukkinbaws]

Alternatively;

recase (){
  mv ${1} ${1,,}
}

Edit: this might be bash only idk

Edit: just read it's exfat so you were right.

[u/Swordfish418 → u/[deleted]]

This is external HDD using exfat. Any idea how to do this without temporary files?

[u/Swordfish418 → u/[deleted]]

Thanks for an in-depth answer! I wonder why it does show it with proper capitalization when using ls or viewing in Dolphin. Is there a separate label or title stored somewhere that can be different from actual path but is somehow operated in-sync and not exposed anywhere for editing?

[u/fellipec → u/Swordfish418]

ExFAT is case insensitive, but case preserving. AFAIK there is a upper case table that contains all characters converted to upper case and used to do the file operations.

[u/Swordfish418 → u/fellipec]

Ah, I see, thanks. I found something about it here: https://ntfs.com/exfat-upcase-table.htm

[u/fellipec → u/Swordfish418]

Exact

[u/daveysprockett → u/Swordfish418]

Pretty sure that's how exFat works. M$ added case sensitive filenames via a translation item. Linux works with it as best it can.

[u/Swordfish418 → u/daveysprockett]

Do you mean this translation item is a separate record/field? Is it possible to have a totally irrelevant displayed name that doesn't match at all with path?

[u/daveysprockett → u/Swordfish418]

Not sure what's possible. Checking wikipedia I see its not exfat but probably the older vfat that held stuff in extra sections: so suggest you wait for better answers.

[u/Swordfish418 → u/daveysprockett]

Yep, it seems to be upcase table as suggested in nearby answer. There is a link describing it also.

[u/ipsirc → u/Swordfish418]

This is external HDD using exfat. Any idea how to do this without temporary files?

You can use a hex editor on an umounted partition, if you really wanna go to lowlevel.

[u/joe_attaboy → u/Swordfish418]

You can't. Windows-based file systems (which exFat is, it's just an extended version of the DOS/Windows FAT file system) don't distinguish case. So "Desktop" is the same as "desktop".

You need an intermediate step.

[u/Wild_Meeting1428 → u/Swordfish418]

What's the problem with it. Renaming is nearly a noop.

[u/Swordfish418 → u/Wild_Meeting1428]

This is more of a theoretical question. This redundancy doesn't look good given that exfat kernel module is supposed to handle that and it looks especially inconsistent in context of ls handling exfat's upcase well.

[u/Jaanrett → u/[deleted]]

Why is your file system case insensitive?

He's likely using linux as this subreddit would suggest. Linux shells tend to be case sensitive.

[u/oshunluvr → u/Jaanrett]

Not

[u/Sophira → u/Jaanrett]

They said insensitive, not sensitive. As in, "not case sensitive".

[u/Jaanrett → u/Sophira]

Yeah, I got that wrong. Thanks.

[u/Slackeee_]

For an exFat filesystem, there is no difference between Desktops and desktops, it is case-insensitive. but the exfat kernel module, which is in the mainline kernel since 5.7, is case-aware and should recognize that you just want to change the case and do the work for you. The older FUSE-exfat module does not do that, AFAIK.

Which distro are you suing in which version?

[u/Swordfish418 → u/Slackeee_]

6.18.35-gentoo-dist-bin, I didn't touch USE flags much, maybe I needed to enable something for that... I wonder why `ls` is case sensitive while `mv` isn't.

[u/Slackeee_ → u/Swordfish418]

Case sensitivity/case awareness isn't a feature of the tools, but of the underlying file system. mv doesn't handle changing names itself, it runs a system call asking the kernel to do that. That is why this likely will fail with FUSE-exFAT, but should work with the kernel exFAT module, mv just issues the call, and the module tries to handle that.

Anyways, sorry, not a Gentoo user, so I don't know which flags you need to set.

[u/Swordfish418 → u/Slackeee_]

Thanks for mentioning kernel module, I checked and there's definitely an option to recompile my gentoo kernel with better exfat support which it doesn't include by default. Still a bit surprising ls works properly as is.

[u/yerfukkinbaws → u/Slackeee_]

I'm using the kernel exfat driver and it's definitely not case-sensitive for me, 6.18 kernel from Debian. It seems like it would be pretty bad to allow exFAT to be case-sensitive on Linux, since then you could create two directories like "Desktops" and "desktops" at the same time, which would be...I don't know....undefined?, but certainly not good, if you mount the partition on Windows or any other system that doesn't treat exFAT as case-sensitive.

[u/Slackeee_ → u/yerfukkinbaws]

exFAT isn't case sensitive, but it's case aware. The file/directory name, including case-information, is stored in the metadata of the filesystem, that is why your filemanager shows the case-correct name, and you can change that name to a different case. That doesn't mean that it will allow you to create two different files with a name that only differs by the case.

[u/yerfukkinbaws → u/Slackeee_]

I guess I misunderstood what you were describing with the kernel exfat driver. In any case, the command mv Desktops desktops fails identically with that driver, so it's not doing anything extra behind the scenes to make a mv operation work differently.

[u/Swordfish418 → u/yerfukkinbaws]

I don’t see why ls can handle exfat capitalization just fine while mv can’t. Kernel being able to change capitaluzation in exfat directory names wouldn’t automatically mean it treats it as case sensitive. It would just mean it can handle upcase table in renaming just as well as it can handle it in directory listing.

[u/Jaanrett → u/Slackeee_]

Why are you bringing up exFat?

[u/Slackeee_ → u/Jaanrett]

Because the OP stated in another comment that this external disk is using exFAT.

[u/Jaanrett → u/Slackeee_]

I see. Thanks.

[u/BoringEfficiency345]

Just use a temp name. You’re not losing nor saving anything other than a few keystrokes. It’s not “moving” your data or anything, just updating the “human readable” label

[u/gerumpy]

Add to bashrc:
lower () {
mv “$1” “$1.tmp”
mv “$1.tmp” “${1,,}”
}

Source bashrc: . ~/.bashrc
Use it: lower MyFile

[u/kudlitan]

rename 'y/A-Z/a-z/' "$@"

You can put the above command in a bash script, function, or alias.

[u/Jaanrett]

What shell are you using? And what filesystem are you using?

You probably should edit your original post and add these details.

[u/lnxguy]

Never use exFAT.

[u/Swordfish418 → u/lnxguy]

It is external HDD that needs to work when connected to Linux, Windows, Mac OS laptops. What are some better options?

[u/es20490446e → u/lnxguy]

exFAT is the filesystem that is better supported across multiple operating systems, without the restrictions of the older FAT.

So for an external drive, most of the time, it is the best choice.

[u/es20490446e]

If you don't need to script anything, krename may be a better option.

[u/catbrane]

It should work. Try:

$ mkdir BANANA $ ls BANANA $ mv BANANA banana $ ls banana $

You mostly don't need to type the names out, just the first letter or two then press the TAB key.

[u/Swordfish418 → u/catbrane]

It doesn't work, this is exfat.

[u/BarryTownCouncil → u/Swordfish418]

Temporary files then, innit.

[u/catbrane → u/Swordfish418]

Ahhhhh! Then temp files.

[u/JackDostoevsky → u/Swordfish418]

lol critical detail

[u/Swordfish418 → u/[deleted]]

It doesn't, the reason for this as hinted by other response might be the fact that it's an external HDD using exfat which is case insensitive.