I have a folder with multiple files in it, and I want to append .mp3 extension at end of each file. is there any way to rename all these files with one command.?
Assuming the files don't already have any extension at all, then run this from the directory containing the files :-
for file in * ; do mv "$file" "$file".mp3; done
If you want to be extra safe, do this instead :-
for file in * ; do cp "$file" "$file".mp3; done
This will make copies of the files and add .mp3, instead of renaming them. You can always delete the originals afterwards.
Or if you want a graphical interface for mass renaming of files, then have a look at PyRenamer in the Software Centre.