Attempting to only copy files that have changed within the last day while maintaining folder structure

Question

I'm attempting to find and copy files that have been modified within the last day. While doing that I'm trying maintain folder structures under dir1. There are many subdirectories under dir1 and data files within those.

Below is what I cobbled together so far but apparently mtime is not updated on directories if the contents of a file is updated. Also I believe this cp command will copy all of the files in a directory rather than just those that have changed.

find /NAS/data/dir1 -type d -mtime -1 -exec cp -at /mnt/databackup/dir1 {} +

If I used -type f it would not retain the folder structure.

Answer 1

You could use find ... -type f, with a bash for-loop. In the loop, a combination of mkdir -p and dirname would let you recreate the folder structure, before simply copying each file with cp.

#!/bin/bash

dirA="/NAS/data/dir1/"
dirB="/mnt/databackup/dir1/"
while read -r file
do
    relative="${file##"$dirA"}"
    newfile="$dirB$relative"
    echo mkdir -p "$(dirname "$file")"
    echo cp -at "$file" "$newfile"
done < <(find "$dirA" -type f -mtime -1)

• read is a bash builtin. It is classically used with -r to avoid some edge-case problems. It reads one line (at a time) from it's stdin. Here, that stdin is the output of find.
• ${var##string-to-remove} is a form of parameter substitution
• newfile="$dirB$relative". This is a classical bash concatenation
• $(). This bash construct is called command substitution
• mkdir -p create a directory and all it's ancestors as needed
• cmd < file this is a classic redirection
• <(cmd) this is called process substitution. It substitute a filename as handle to the stdin [>()] or stdout [<()] of a command.

You can use explainshell.com to get more detailed explanations.