Question

I have many files with .txt extension.
How to remove .txt extension for multiple files in linux?

I found that

rename .old .new *.old

substitutes .old extension to the .new

Also I want to do this for files in sub-folders.

Answer 1

rename is slightly dangerous, since according to its manual page:

rename will rename the specified files by replacing the first occurrence of…

It will happily do the wrong thing with filenames like c.txt.parser.y.

Here’s a solution using find and bash:

find -type f -name '*.txt' | while read f; do mv "$f" "${f%.txt}"; done

Keep in mind that this will break if a filename contains a newline (rare, but not impossible).

If you have GNU find, this is a more solid solution:

find -type f -name '*.txt' -print0 | while read -d $'\0' f; do mv "$f" "${f%.txt}"; done