R-regex: match strings not beginning with a pattern

Question

I\'d like to use regex to see if a string does not begin with a certain pattern. While I can use: [^ to blacklist certain characters, I can\'t figure out how to

Answer 1

Yeah. Put the zero width lookahead /outside/ the other parens. That should give you this:

> grepl("^(?!hede).*$", "hede", perl = TRUE)
[1] FALSE
> grepl("^(?!hede).*$", "foohede", perl = TRUE)
[1] TRUE

which I think is what you want.

Alternately if you want to capture the entire string, ^(?!hede)(.*)$ and ^((?!hede).*)$ are both equivalent and acceptable.