Character Classes

• There are a bunch metasymbols that represent character classes:

  Symbol	Definition
  \d	[0-9]
  \s	[ \t\n\r\f]
  \w	[a-zA-Z0-9_]

• The complements of these classes can be accessed by using upper-case versions of the metasymbols. e.g. \D matches any non-digit character, [^0-9]
• There are also unicode and POSIX character classes