Differences between RE2 and PCRE

DataSift makes use of the Google RE2 regular expression engine. This has a subtly different syntax in some cases and a slightly different function set to the PCRE library which is the most common.

The RE2 engine omits some features:

  • most VIM-specific repetition commands
  • no possessive repetitions
  • some grouping formatting (see details below)
  • several empty string selectors, including all VIM-specific ones
  • backreferencing escape sequences
  • Perl-style spacing character classes
  • all VIM-specific flags and most VIM-specific character classes

For the full differences between PCRE and RE2, check out the syntax page on Google Code.

Make sure you've read our page on special characters.