How to compress all directories that weren't used in the last month?

Question

How can I compress all the directories that do not contain at least one file used in the last month?

Answer 1

You need a two-step approach. But why do you really want to do this in shell? It will be a lot faster when you actually implement this directly, say with a python script. The reason is that you can stop scanning a directory if you have found a "recent" file (except for subdirectories that you might still want to archive).

The naive shell-based approach would be to find all folders, then rescan each folder for the recent files. Something like this (for zsh)

find /start -depth -type d -print | while read dir; do
  files=$( find $dir -type f -mtime -30 )
  if test -z "$files"; then
    echo "Unused dir: $dir"
  fi
done

But again, note that this is not very efficient, and will also contain redundant entries (if a directory is "unused", it will also list all subdirs.)