Replace a regular expression within vim with an output produced by a console command with the expression as its argument?

Question

let's say I have a file with the following content:

This is a _file_ which has some _special_ keywords, that I would _like_ to replace.

I can do a search and replace of the speical keywords with "%s/_*_/something", but I would like "something" to be an output of an external command. Is this possible in vim, or do I need to awk it?

Answer 1

Yes, you can. See :help sub-replace-special; the \= allows you to replace with a Vim expression. And system() can execute an external command and return its output. See my trivial example with hostname. Note that I had to use substitute() to get rid of the trailing newline character(s) in the output.

:%s/_[^_]*_/\=substitute(system('hostname'),'\n','','g')/g

^{PS: I also corrected your regexp pattern to match your example.}