How can I use Regex in helpgrep?

Question

I would like to use Regex in helpgrep. For example, searching for lines or sections that contain two words. Something like :helpg 'word1' & 'word4' to find this line as my result: word1 word2 word3 word4. Or another example for lines or sections containing word1 or word4.

Answer 1

You can use regexps in :helpgrep, you only need to provide a valid regular expression. Your 'word1' & 'word4' does not do what you describe. To match both "word1" and "word4" on the same line or either of them, try the respective

:helpgrep word1.*word4
:helpgrep word1\|word4

The regexps explained: The first line will match "word1" followed by any number of any character, followed by "word2".
The second line will match "word1" OR "word2", the \| being the OR operator in Vim's dialect of regular expressions (other dialects use a plain | so you may have seen this).

As I said, this works on lines and things get complicated quickly when trying to get matches within a section or paragraph. It's probably easier to search from there or actually reading the whole paragraph. I like doing so because I tend to learn new stuff this way.

A full description of regexps is beyond the scope of an answer on this site. To familiarize yourself with (Vim's dialect of) regular expressions, read :help regexp.