Directory Scrubber

When I got in to organizing my music collection, I often found myself dealing with a couple pernicious directory structures, one of them being large trees of empty directories.

rmdir does not have built-in support for recursive deletion, and rm does not offer a means to remove only directories.

I also ran in to trees of directories with sidecar files or other unwanted files. A simple recursive RM could get rid of these, but one would have to make sure that there was nothing in the structure that was actually useful.

Initially, I wrote a fish script, known as rmempty that was a somewhat painfully slow recursive shell script involving find and some odd pipe abuse. This later mutated in to a simpler fish function, granted that it had less functionality.

function rmempty --description 'Trim empty trees'
  # Create a list of targets with child directories listed before their parents
    set __rme_targets       (find $argv -depth -type d | tail -n +2)
    set __rme_total_success yes

    for target in $__rme_targets
        # If the target is a nukable target, recursively delete it
        if contains -- (basename "$target") $rm_empty_nuke
            rm -rv "$target"
        else # If it is an average directory, run rmdir on it
            if not rmdir "$target" 
                set __rme_total_success no

    if [ $__rme_total_success != yes ]
        echo rmempty: unable to remove all children

This went relatively unneeded for a while, until I needed to clean up a bunch of files with specific extensions in a given tree. Due to the number of files, it would be impractical to use a recusive glob (rm **.extension) to pass them all as arguments to rm, as it would both take a moment for the shell to collect the list of files, and then the kernel would need to support passing that many arguments to a command. Alternatively, some manner of recursive script could be written that invokes rm on each file, but I would rather run this all in a single process.

All of this ultimately led to scrub.c, a simple program that is safe in its nature and quite fast. scrub.c is around 585 lines long as of writing, a lot of it due to formatting (though nobody cares about line count). It allows for both file names and file extensions to be specified. These file extensions and names will be removed if they exist in a tree. If a directory is empty once processed, it will be removed. Directories that were already empty will also be removed. An option will likely be added to preserve directory structure and remove only files.

The manner in which it operates is recursive, and therefore quite simple:

function process_file (file)
  if (file.is_directory)
    if (file.is_empty) 
    end if
  if (should_remove(file)) 
  end if

Getting scrub.c

You can get scrub.c from the github repository. I have pre-compiled binaries for x86_64, x86, and a copy compiled against musl-libc for x86_64.

Compiling is rather simple, considering that scrub.c has no dependencies outside of a libc supporting unlink, rmdir, readdir, stat, closedir, basename, and other familiar functions.

Simply run gcc -o scrub scrub.c and you are good to go.

Using scrub.c

Scrub can accept more than one file or directory as a paramater. If passed a file, it will check if the file may be removed according to the specified parameters. If it may be removed, scrub will unlink it.

The following options are accepted:

- -cext     --clobber-extension=ext 

  This will remove all files with the given extension 

- -Cname    --clobber-name=name 

  This will remove all files with the given name 

- -H        --preserve-hidden

  If specified, scrub will _not_ remove any _directories_ whose name starts with `.`

- --simulate

  If specified, scrub will output actions but not take them. This will have an effect on 
  whether a directory will be determined as empty or not, and is meant for debugging 

- --verbose

  Output every action that scrub takes 

An example invocation that removes all nfo files and files named cover.jpg would look like this:

scrub -cnfo -Ccover.jpg folder1/ folder2/

If scrub was able to remove everything up to, and including, those files and directories passed as arguments, it will return 0. Otherwise, an appropriate status is returned.