install tool to find duplicate files
sudo apt install fdupes
find duplicates
fdupes firstDir --recurse secondDir > duplicates
delete empty directories
find ./ -empty -type d -delete
display nuber of files groped by the extension
find . -type f | sed -e 's/.*\.//' | sed -e 's/.*\///' | sort | uniq -c | sort -rn
delete json files recursive in current directory
find ./ -name "*.json" | tr '\n' '\0' | xargs -0 rm