regexre2

Negate match in RE2 syntax?

How can I write a regex in RE2 for "match strings not starting with 4 or 5"?

In PCRE I'd use ^(?!4) but RE2 doesn't support that syntax.

Solution

  • You can use this regex:

    ^[^45]

    ^ matches start and [^45] matches anything but 4 or 5 at start.