regex-in-brief.txt

Matchers
^
  Match starting position
.
  Match any single character, enclose in bracket for literal dot
  a.c -> "abc", etc.
  [a.c] -> "a", ".", "c"
[ ]
  Match single character, or character within range
  [abc], [a-c] -> "a", "b", "c"
  [a-cx-z] -> "a", "b", "c", "x", "y", "z"
[^ ]
  Match single character not contained in brackets
  [^a-y] -> "z", etc.
$
  Match ending position
( )
  Subexpression, can be recalled later with $1, $2, etc.
\n
  Matches whatever nth marked subexpression matched.
*
  Matches preceding element zero or more times
  12* -> "1", "12", "122", etc.
  [ab]* -> "", "a", "aa", "ab", "abb", etc.
  (ab)* -> "", "ab", "abab", "ababab", etc.
{m,n}
  Matches preceding element at least m but not more than n times
  a{2,5} -> "aa", "aaa", "aaaa", "aaaaa"
?
  Matches preceding element zero or one time
  ab?c -> "ac", "abc"
+
  Matches preceding element one or more times
  ab+c -> "abc", "abbc", "abbbc", etc.
|
  Choice
  abc|xyz -> "abc" or "xyz"

Character Classes
\w
  [A-Za-z0-9_]
\W
  [^A-Za-z0-9_]
\d
  [0-9]
\D
  [^0-9]
\s
  [ \t\r\n\v\f] white-space
\S
  [^ \t\r\n\v\f] non white-space