Script to delete all files and keep only latest file

Question

Any advise on how to do delete all files and only keep the latest file in each sub-directories, starting from a specific directory? This is what I have tried:

#!/bin/bash

find /home/ftp/ -type f | while IFS= read -r line
do
  find "$line" -type f | head -n -1 | while read file
  do
    #rm -f "$file"
    echo "$file"
  done
done

I have 2 sub-directories in /home/ftp/upload and /home/ftp/download. Both sub-directories have 2 files in each of the sub-directories.

When tested the script above, there is no file name echo out.

Answer 1

With zsh, from the current directory:

for dir (**/*(N/)) {
  files=($dir/*(N.om))
  (($#files > 1)) && echo rm -f -- $files[2,-1]
}

If you want hidden directories and files considered, add the D glob qualifier.

That only considers regular files. If you want other types of files like devices, sockets, named pipes, or if you want to follow symlinks, it can be adapted with more glob qualifiers.

Remove the echo to actually do the task.

With recent GNU tools and a POSIX shell:

(export LC_ALL=C
find . -type f -printf '%T@\t%p\0' |
  sort -rzn |
  cut -zf2- |
  gawk -v RS='\0' -v ORS='\0' '
    match($0,/.*\//) && n[substr($0,1,RLENGTH-1)]++' |
  xargs -r0 echo rm -f
)