cp from different directory to one directory certain files

Question

I want to do the following.

I want to copy from a remote FTP server every day certain files. This FTP directory is mounted. Every day a directory is created and within that directory I need 3 files of the 5

dir1
dir2
dir3

I want to copy every day the files with certain extensions to dir999

cp */*.img /dir999 

But will that copy every day all files again ? as its a lot i only want to do the changes.

Answer 1

Many implementations of cp like FreeBSD, GNU and MacOS have an option -n to skip existing files. So with

cp -n */*.img /dir999

you will only copy new files. Note that changed files won't get updated in the destination directory. If you want this, you'd need a different solution.