Use bash shell to implement recursive copies of files in a directory

Objective
There is a problem with working today, if you copy the file in directory A to directory B (without the file in directory B), and keep the file structure in directory A. The project focuses on the following:

You need to keep the structure of the file in directory A in directory B. Suppose that a directory file A/test/1.txt, transfer to directory B should be b/test/1.txt. You also need to consider whether there is a test directory in directory B, and the multilevel directory should consider recursion. (Fortunately, it's easier to write a recursive traversal of a directory in the Bash shell.) ）
You need to consider whether the file in a has a file with the same name in B, and if it does, it does not need to be copied.

The project requirements sample diagram is as follows:

Realize
Project requirements have, know the design to recursion, the code is very good to write. Here is a demo example for everyone to refer to.

#!/bin/bash     function Recursive_copy_file ()  {    dirlist=$ (ls $) for    name in ${dirlist[*]}     do If [-f $1/$name];       then # If it is a file and the file does not exist, copy the        if [!-f $2/$name], then         CP $1/$name $2/$name        fi     elif [-D $1/$name ];       then # If it is a directory, and the directory does not exist, create a directory        if [!-D $2/$name]; then         mkdir-p $2/$name        fi       # recursive copy        Recursive_copy_file $1/$name $2/$name      fi done   }     source_dir= "/tmp/test/system" dest_dir= "/tmp/test/ Systemback "    recursive_copy_file $source _dir $dest _dir