Is there a way to undo a batch-rename of file extensions?

Ok so I kinda dropped the ball. I was trying to understand how things work. I had a few html files on my computer that I was trying to rename as txt files. This was strictly a learning exercise. Following the instructions I found here using this code:

for file in *.html
do
 mv "$file" "${file%.html}.txt"
done

produced this error:

mv: rename *.html to *.txt: No such file or directory

Long story short I ended up going rogue and renaming the html files, as well as a lot of other non html files as txt files. So now I have files labeled like

my_movie.mp4.txt
my_song.mp3.txt
my_file.txt.txt

This may be a really dumb question but.. Is there a way to check if a file has two extensions and if yes remove the last one? Or any other way to undo this mess?

EDIT

Doing this find . -name "*.*.txt" -exec echo {} \; | cat -b seems to tell me what was changed and where it is located. The cat -b part is not necessary but I like it. This still doesn't fix what I broke though.

Solution

I'm not sure if terminal can check for extensions "twice", but you can check for . in every name an if there's more than one occurence of ., then your file has more extensions. Then you can cut the extension off with finding first occurence of . in a string when going backwards... or last one if checking characters in string in a normal way.

I have a faster option for you if you can use python. You can strip the extension with:

for file in list_of_files:
    os.rename(file,os.path.splitext(file)[0])

which can give you from your file.txt.txt your file.txt

Example:

You wrote that your command tells you what has changed, so just take those changed files and dump them into a file(path to file per line). Then you can easily run this:

with open('<path to list>') as f:
    list_of_files = f.readlines()
for file in list_of_files:
    os.rename(file.strip('\n'), os.path.splitext(file.strip('\n'))[0])

If not, then you'd need to get the list from python:

import os
results = []
for root, folder, filenames in os.walk(<your path to folder>):
    for filename in filenames:
        if filename.endswith('.txt.txt'):
            results.append(os.path.join(root, filename))

With this you got a list of files ending with .txt.txt like this <your folder>\\<path_to_file>.

Get a path to your directory used in os.walk() without folder's name(it's already in list) so it'll be like this:

e.g. os.walk('/home/me/directory') -> path='/home/me/' and res is item already in a list, which looks like directory/...

for res in results:
    path = '' # set the path here
    file = os.path.join(path,r)
    os.rename(file, os.path.splitext(file)[0])

Depending on what files you want to find change .txt.txt in if filename.endswith('...') to whatever you like and os.rename() will take file's name without extension which in your case means it strips the additional extension you don't want to have.