ag Silver Searcher: rules for lookahead/lookbehind patterns?

Question

I\'m using ag in Vim with good results for string/file search.

However, there seems to be not much documentation how patterns are constructed for ag.

<

Answer 1

The Silver Searcher tool uses PCRE (Perl-Compatible Regular Expression) syntax. So instead of Vim's \ze, you need to use the Perl syntax for positive lookahead: (?=pattern). (The corresponding lookbehind for \zs would be (?<=pattern).)

I'm showing your example on the command-line, but it should be identical from within Vim:

$ ag 'Pragmatic(?= Vim)'