Copy and rename on collision

Question

I'd like to merge the content of these folders with a command line.

.
├── folder1
│   │ file.txt
│
├── folder2
│   │ file.txt
│
└───folder3
    │ file.txt

How can I do this ?

Answer 1

Finally I can do this with cp and its --backup flag.

cp --backup=numbered */*.txt new_directory/

Answer 2

The following command-line loop will copy the (top-level) contents of every folder named "folder*" in your current directory into a directory named "new_directory". The /* glob will, by default, not match "dot files"; use shopt -s dotglob if you want to change that behavior. If the same (base) filename already exists in new_directory, then it prefixes the destination file with the originating folder (and an underscore), in order to make it unique.

All in one line:

for f in folder*/*; do [ ! -e "new_directory/$(basename "$f")" ] && { cp "$f" new_directory/; continue; }; [ -e "new_directory/$(basename "$f")" ] && cp "$f" "new_directory/$(dirname "$f")_$(basename "$f")"; done

Broken out for readability:

for f in folder*/*
do 
  [ ! -e "new_directory/$(basename "$f")" ] && { cp "$f" new_directory/; continue; }
  [ -e "new_directory/$(basename "$f")" ] && cp "$f" "new_directory/$(dirname "$f")_$(basename "$f")"
done

If you intent instead to move the files from their original locations, simply change the cp's to mv's.