With unix cp you can do

cp -Rf oneDir/ twoDir/

which copies all the files in oneDir into twoDir. When I do:

cp('-Rf', 'oneDir/', '/twoDir/');

nothing gets copied, I have to do

cp('-Rf', 'oneDir/*', '/twoDir/');

from man cp

If source_file designates a directory, cp copies the directory and the entire subtree connected
at that point. If the source_file ends in a /, the contents of the directory are copied rather
than the directory itself.