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In this article we shall try to undestand grep and extended grep(grep with '-E' option).

 -E, --extended-regexp
              Interpret PATTERN as an extended regular expression (ERE, see below).  (-E is specified by POSIX.)


Basic vs Extended Regular Expressions
       In basic regular expressions the meta-characters ?, +, {, |, (, and ) lose their special meaning; instead use the backslashed versions \?, \+, \{, \|, \(, and \).

       Traditional egrep did not support the { meta-character, and some egrep implementations support \{ instead, so portable scripts should avoid  {  in grep -E patterns and should use [{] to match a lite ... Read more »

Category: Open System-Linux | Views: 2056 | Added by: shanky | Date: 2015-07-12 | Comments (0)