How to get put the result of a shell command in a variable?

Question

I would like to capture the result of a shell command into a vim variable inside of my vimrc file.

I tried using let myvar = system("DIR") however it seems to crash vim when I put it in my vimrc file. I launch vim and then it just returns immediately without any error message.

So instead I was wondering if I can do something like let exe_path = <expr> :!pwd ? This is obviously the wrong way to do it so I was wondering if something like that is possible?

Answer 1

system() is the right function; it should work fine also inside ~/.vimrc, but is best avoided as each external command delays Vim's startup and makes the user wait.

Ideally, you'll be able to only invoke the external command once it's required for a user interaction (i.e. lazily) - and then cache the information in case it's needed again.

If you absolutely need the information on startup already, and to work around your problem, you can hook into the VimEnter event that is fired at the end of initialization:

:autocmd VimEnter * let myvar = system('pwd')

^{The pwd is only an example; you'd better use the built-in getcwd() instead.}