How do I join/reduce a list of strings to a single string?

Question

I want to convert this

builtins.readFile ../../dotfiles/vim/commands.vim + "\n" +
builtins.readFile ../../dotfiles/vim/keybindings.vim + "\n" +
builtins.readFile ../../dotfiles/vim/plugins.vim

into something more dynamic. This is what I've got so far. It evaluates to a list of strings.

map
  ( fileName: builtins.readFile ( ../../dotfiles/vim + "/${fileName}" )
  ( builtins.AttrNames ( builtins.readDir ../../dotfiles/vim ) )

Answer 1

With lib.concatStrings.

# Generic:
lib.concatStrings [ "a" "b" "c" ] # Returns "abc"

# Specific:

lib.concatStrings (
  ( map
    ( fileName: builtins.readFile ( ../../dotfiles/vim + "/${fileName}" )
    ( builtins.AttrNames ( builtins.readDir ../../dotfiles/vim ) )
  );