How do I make “cp” in OS X not delete files?

Question

Here's the best way to describe this:

dirA
   dir1
      file1.txt
      file3.txt
dirB
   dir1
      file1.txt
      file2.txt

I want to copy the contents of dirB into dirA. cp -R dirB/* dirA would delete dir1 and copy the files, resulting in:

dirA
   dir1
      file1.txt
      file2.txt

But I want to merge them (like it would on Windows) and end up with:

dirA
   dir1
      file1.txt
      file2.txt
      file3.txt

Suggestions? I've tried ditto, but that seems to ignore the recursive part and just dump all the files in the top-level folder.

Answer 1

Don't use cp. Use rsync.

(Apple dev link.)

Answer 2

cp does not delete files.

Answer 3

Use -i option to cp

     -i    Cause cp to write a prompt to the standard error output before
           copying a file that would overwrite an existing file.  If the
           response from the standard input begins with the character `y'
           or `Y', the file copy is attempted.  (The -i option overrides
           any previous -n option.)

Answer 4

There's gotta be an elegant way, but as a quick hack: remove write permission from the files in dir1, then do a cp -r.

Answer 5

dirA dir1 file1.txt file3.txt dirB dir1 file1.txt file2.txt

I would do it this way:

$ cd dirA
$ tar cf - | (cd .../dirB ; tar xf -)

Files get overwritten, directories don't.

Answer 6

Erics solution worked but I had to tweak syntax a little:

$ cd dirA
$ tar -cf - ./* | (cd .../dirB ; tar -xf -)

Answer 7

I'm doing something similar with an export script. Here is the command I'm using:

cp -R demo_files/. demo

This will merge the files in demo_files with the files in demo. It shouldn't overwrite anything.