If you want modern regexp syntax then forget egrep/grep -E and use grep -P for Perl Compatible Regular Expressions. PCRE is the most commonly used regex syntax

If you want modern regexp syntax then forget egrep/grep -E and use grep -P for Perl Compatible Regular Expressions. PCRE is the most commonly used regex syntax for modern programming languages, eg Python, Go (mostly) etc and grep -P will save lots of annoyance if you use one of these!