This is when you learn that not all implementations are the same, and realize it's better to read the documentation for your particular implementation. I'm gue

This is when you learn that not all implementations are the same, and realize it's better to read the documentation for your particular implementation. I'm guessing your grep defaults to POSIX EREs, but always check the manual. The behavior of multiple adjacent duplication symbols ( '+', '*', '?', and intervals) produces undefined results. http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap09.html http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_...