Implement a recursive copy of a file in a directory using the bash Shell _linux Shell

Objective
a problem has been encountered at work today, if you copy the files from directory A to directory B (without the file in directory B) and keep the files in directory A. The focus of the project is as follows:

You need to keep the structure of the file in directory A in directory B. Suppose 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 multi-level directory should consider recursion. (Fortunately, it's easy to write a directory recursive traversal in the Bash shell.) ）
You need to consider whether a file in B already has a file with the same name, and if it exists, you do not need a copy.

Sample project requirements are shown below:

Realize
the project needs to have, know the design to recursion, the code is very good to write. Here is a demo sample for your reference.

 #!/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, direct copy 
        if [!-f $2/$name]; 
          then CP $1/$name $2/$name 
        fi 
      elif [-D $1/$nam E]; Then 
        # if it is a directory, and the catalog 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