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?

to make matters worse, you'll also need to worry about the sort functionality if you have more than one digit in the sequence. FILE_1-10 comes lexicographically before FILE_1-2 . Padding with zeros (eg FILE_1-002 ) would make numeric and lexicographic order consistent. — erik258
– erik258, Commented Sep 27, 2019 at 15:04
For a general answer, yes. In my case the highest number is fortunately FILE_3-5. I hope this helps to keep it simple. — And
– And, Commented Sep 27, 2019 at 15:07
You mention branching subdirectories, but they need to be considered when finding "the last file", or is the "last file" the one in each separate subdirectory? — Jeff Schaller
– Jeff Schaller ♦, Commented Sep 27, 2019 at 16:13
There's a slight inconsistency; your example command shows ls ... FILE_*.txt while your sample filenames do not end in .txt — Jeff Schaller
– Jeff Schaller ♦, Commented Sep 27, 2019 at 16:16
You are correct, I edited that out. And It's always the last file within each separate subdirectory. — And
– And, Commented Sep 30, 2019 at 8:01

xenoid · Accepted Answer · 2019-09-30 11:52:14Z

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.

I put the first and the third line into the script and then executed the last line and I'm getting the error find: ‘{the_script}’: No such file or directory. I put the script into the parent folder where I am executing the find command. What do I do wrong? — And
– And, Commented Sep 30, 2019 at 10:24
{the script} is of course a place holder for your actual script name. Note that your script is also assumed to loop over the stems: line 3 is executed once for each stem found with line 1. — xenoid
– xenoid, Commented Sep 30, 2019 at 11:17

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