How to use find with regex to delete files beginning with certain letters

Question

I have a nested directory structure that looks like this:

top_dir
└── nested_1
    └── nested_2
        ├── a_file.txt
        ├── b_file.txt
        ├── directory
        ├── other_directory
        ├── y_file.txt
        └── z_file.txt

I want to delete the files inside nested_2 that don't start with A-M, and leave the directories alone. So I want to delete y_file.txt and z_file.txt.

I need to run the find + regex command in top_dir.

I've tried multiple versions of this:

find nested_1/nested_2 -maxdepth 1 -mindepth 1 -type f -regex "nested_1\/nested_2\/.*^[a-m]" #-delete

It doesn't seem to matter what regex I use - the only one that produces any result at all is

find nested_1/nested_2 -maxdepth 1 -mindepth 1 -type f -regex ".*" #-delete

which just gives me a list of all the files in the directory with the leading nested directories (as expected).

Testing it out on regexr hasn't helped either.

What am I missing here?

Answer 1

1. ^[a-m] should be [^a-m].
2. After the first letter there may be the rest of the filename, so you need .* after [^a-m], not before.
3. These backshlashes are not needed (they don't hurt though).

find nested_1/nested_2 -maxdepth 1 -mindepth 1 -type f -regex "nested_1/nested_2/[^a-m].*" #-delete

Notes:

• Linux and its filesystems are case sensitive. Things "that don't start with A-M" would be [^A-M].*.
• Sometimes [^a-m] (or [^A-M]) may not be what you think.