Regular Expressions

     Regular expressions are the extended kind  found  in  egrep.
     They are composed of characters as follows:

     c         matches the non-metacharacter c.

     \c        matches the literal character c.

     .         matches any character except newline.

     ^         matches the beginning of a line or a string.

     $         matches the end of a line or a string.

     [abc...]  character class, matches  any  of  the  characters
               abc....
     [^abc...] negated character  class,  matches  any  character
               except abc... and newline.

     r1|r2     alternation: matches either r1 or r2.

     r1r2      concatenation: matches r1, and then r2.

     r+        matches one or more r's.

     r*        matches zero or more r's.

     r?        matches zero or one r's.

     (r)       grouping: matches r.

• la matches all strings containing the substring la, e.g. Klaus, Nikolai, Clarence etc.

• (Boris)|(Phil) matches all strings containing the substring Boris or the substring Phil, e.g. Boris, Philippe, Phil, Philip, etc.

• ^12..$ matches all strings beginning with 12 followed by only two further characters, e.g. 1200, 1201, 12AZ, etc.

• ^....$ matches all strings with length 4, e.g. Ruth, John, Henk, Rick, etc.