User:Swapnil durgade/Regular Expressions Notes

c         matches the non-metacharacter c.       \c         matches the literal character c.       .          matches any character including newline. ^         matches the beginning of a string. $         matches the end of a string. [abc...]  character class, matches any of the characters abc....       [^abc...]  negated character class, matches any character except abc....       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.       r{n} r{n,} r{n,m}    One  or two numbers inside braces denote an interval expres- sion. If there is one number in the braces, the  preceding regular expression r is repeated n times. If there are two numbers separated by a comma, r is repeated n to  m  times. If there  is  one  number  followed  by  a comma, then r is                  repeated at least n times. Interval expressions are only available if either --posix or                 --re-interval is specified on the command line. \y        matches  the empty string at either the beginning or the end of a word. \B        matches the empty string within a word. \<        matches the empty string at the beginning of a word. \>        matches the empty string at the end of a word. \w        matches any word-constituent character  (letter,  digit,  or  underscore). \W        matches any character that is not word-constituent. \'        matches the empty string at the end of a buffer.