Vim get first line in a register

Question

I have a multi-line string that I'm reading by:

let a = getreg('*')

What would be the best way to get the first line of that string? I was hoping I could do something like:

• match
• getbufline

But am having trouble finding the necessary string function to do this. In python it'd be something like: str.split('\n')[0]

If helpful, when I do echom a the output looks like:

Also, what is ^@ in vim? I've seen ^M for linebreak (return) but have never seen ^@ before.

Update: After some investigation it seems like that's the nul or \0 byte, and can be entered in by doing ctrlv ctrl@. And I ended up using this:

let first_line = matchstr(register, '\v<[^\n]+>')

It's very odd that this regex is what's used, as I tried doing something basic like `\v^.+$' and although it would work on a search page, it returned no results when I tried to search the register with it...

Answer 1

Normally I prefer let a = getreg('*', 1, 1)[0] which is a bit shorter than let a = split(getreg('*'), "\n")[0] and does the same thing.

However, in your case the register contents for some reason contains Nul bytes (see :h NL-used-for-Nul). Hence you have to split on Nul manually: let a = split(getreg('*'), '^@')[0]

Answer 2

^@

The null byte 0x00. Due to various things at the source-code level, newlines get embedded as null bytes in certain things (not all strings, since you can use ^M, as you know).