REGEX character classes

Regex character class can make our life easy, as it makes one small sequence of characters match a larger set of characters. However, character classes can only be used within bracket expressions. For example, [[:upper:]xy] matches all the uppercase letters and lowercase "x" and "y".

Char Class	Description
[:alnum:]	alphanumeric characters [A-Za-z0-9]
[:lower:]	lowercase letters [a-z]
[:upper:]	uppercase letters [a-z]
[:digit:]	digits [0-9]
[:blank:]	Space and tab [ \t]
[:space:]	Space [ ]
[:punct:]	punctuation characters e.g., [][!"#$%&'()*+,./:;<=>?@\^_{}~-]

Example: