read file and store contents in a register

Question

Is there a way in vim to read a file, like with :r, and then store it in some register? and is there a way to do the same, but only with the lines in the file that matches some pattern?

Answer 1

Try this:

:let @x = join(readfile("~/.vimrc"), "\n")

It will read .vimrc to register x.

Answer 2

Using external grep, you could do:

:let @x = system('grep pattern filename')

to place only the lines matching pattern from file filename in register x.

Answer 3

You can create a new buffer with :new, read the file :r <filename>, yank the entire file for a register (say, x) with gg"xyG", and delete the buffer with :q!. If you intend to perform this actions several times you can create a mapping for it.

To do the same with lines that matches a pattern, you can peform a global command (:h :g) before performing the copy to the register.