use find to delete all but last file within subdirectories

Question

I want to free up some space by deleting redundant files within many subdirectories. However I always want to retain the last file of a file stem. For example I have an assortment (next to other files that should not be touched) similar to this:

FILE_1-1 FILE_1-2 FILE_1-3 FILE_2-1 FILE_2-2

within a whole bunch of branching subdirectories. I want to keep FILE_2-2 in this instance, but in another folder it would be FILE_3-1 or whatever. Always the last file. I know how to get rid of all of them using the find command which traverses the subdirectories nicely:

find . -name "FILE_*" -type f -delete

How can I exclude the last FILE_* within each directory where removal happens using the find command? Googling (https://www.unix.com/shell-programming-and-scripting/36639-find-remove-all-but-latest-file.html) turned up the following:

ls -1 FILE_* | sort -r | tail +2 | xargs -i rm {}

But this command does not work with branching directories, does it?

Answer 1

In a directory you can find the "stems" with:

ls * | sed -r 's/[0-9]+$//' | sort | uniq

For each stem you can list all files with the last with:

ls  FILE_1-* | head -n -1

Or if you want to keep the most recent:

ls -rt FILE_1-* | head -n -1

Both commands can be followed by | xargs rm to delete their output

Put all that in a short script(*) and run:

find . -type d -exec {the_script} {} \;

(*) the short script would look like:

#! /bin/bash
cd "$1"  # takes the directory as a parameter
for stem in $(ls FILE* | sed -r 's/[0-9]+$//' | sort | uniq)
do 
    ls -rt ${stem}* | head -n -1 | xargs echo rm 
done

Of course test thoroughly and replace echo rm by just rm when you are confident that it will erase the right files.