How to clean up file extensions?

Question

I have a directories with .MP3 files which I'd like to change the extensions to .mp3. What's the easiest way to do this? I'm think something along the lines of:

find /RootPath -type f -iname "*.mp3" -exec mv {} sed s/.*MP3/\1.mp3/ \; 

...though I know that isn't quite right. :) The substitution isn't correct and I'm not sure how to use both a mv and a sed command with -exec in find.

Would I need a bash script for this?

Answer 1

Here is one way to do this in Bash:

for i in *; do [ "${i/%MP3/mp3}" != "$i" ] && echo "$i" "${i/%MP3/mp3}"; done

I've used echo here so the command itself doesn't do anything but print pairs of files names. If that list represents the changes you want to make, then you can change echo to something like mv -i -- which will then move your files (and prompt you before overwriting).

Brief Explanation:

The for iterates through every file matched by *. Then, we determine if the extension is already lowercase, if it is we move on, if it isn't, we proceed to move it (or echo it, as the case may be). This uses Bash's built in string operations which you can read about here: http://tldp.org/LDP/abs/html/string-manipulation.html

Answer 2

In zsh:

autoload zmv
zmv '(*).MP3' '$1.mp3'   # rename files in the current directory only
zmv '(**/)(*).MP3' '$1$2.mp3'  # rename files in subdirectories as well

Answer 3

Use perl-rename, swiss army knife of file-renaming with regular expressions (on ubuntu, this is bundled with the perl package as prename):

# Replace prename as appropriate (i.e. if you've got it installed under a different name
find /RootPath -type f -iname '*.mp3' -print0 | xargs -0 prename 's/mp3$/mp3/i'

If you're of the careful sort, use the -n and -v options to perl rename to see what it'll actually do.

Answer 4

You could use the rename command for those. For example to change the case of file name extensions from upper to lower, try this:

rename .JPG .jpg *.JPG

Here is some guys tutorial about how he moved from a messy bash script to this simple command for exactly your use-case.

Another fancy command to do this is pax. If you are using ZSH for your shell, you could also use zmove.

Answer 5

You need a script, because "extensions" under Linux are actually just parts of the file name string. You have to do some string manipulation in the script to get the new name.

#!/bin/bash
for NAME in *.JPG
do
    PREFIX=${NAME%.*}
    NEWNAME="$PREFIX.jpg"
    mv "$NAME" "$NEWNAME"
done

The double-quoting is important if you've got file names with whitespace in them. I thought some of the double-quoting was a bit inobvious.