"Linux" copies folder contents to another folder

I always thought CP was a very simple instruction. It turned out to be a pit. Record it.

Folder 1:test1/

Folder 2:test2/

Target: Copy all files and directories in the test1/to test2/

Correct instruction:

CP -RF test1/. test2/

Note that the back of the test1/is a point

The following command is problematic:

CP -RF test1/*  test2/

I have been using this sentence, the results found today, if Test1 is an empty folder, the command will error. But if you replace the *. There is no problem at all.

"Linux" copies folder contents to another folder