Building Simple Character Classes

The most basic type of character class is a set of characters placed side-by-side within square brackets "[]". For example, the regular expression [bcr]at, matches the words "bat", "cat", or "rat" because it uses a character class (that includes "b","c", or "r") as its first character. Character classes only match singular characters unless a quantifier is placed after the closing bracket. For examples using quantifiers with character classes, see Compound Character Classes. The following table shows how to use simple character classes in regex searches.

Note: When placed inside a character class, the hyphen "-" metacharacter denotes a continuious sequence of letters or numbers in a range. For example, [a-d] is a range of letters denoting the continuious sequence of a,b,c and d. When a hyphen is otherwise used in a regex, it matches a literal hyphen.

Using simple character classes to perform regex searches.

Example 1: Use a character class to match all cases of the letter "s".

  • Regex:
    Java[Ss]cript
  • Matches:
    JavaScript
    Javascript
  • Doesn't Match:
    javascript
    javaScript

Example 2: Use a character class to limit the scope of alternative matches on the words gray and grey.

  • Regex:
    gr[ae]y
  • Matches:
    gray
    grey
  • Doesn't Match:
    gry
    graey

Example 3: Use a character class to match any one digit in the list.

  • Regex:
    [0123456789]
  • Matches:
    5 
    0
    9
  • Doesn't Match:
    x
    ?
    F

Example 4: To simplify the previous example, use a hyphen "-" within a character class to denote a range for matching any one digit in the list.

  • Regex:
    [0-9]
  • Matches:
    5 
    0
    9
  • Doesn't Match:
    234
    42

Example 5: Use a hyphen "-" within a character class to denote an alphabetic range for matching various words ending in "mail".

  • Regex:
    [A-Z]mail
  • Matches:
    Email
    Xmail
    Zmail
  • Doesn't Match:
    email
    mail

Example 6: Match any three or more digits listed in the character class.

  • Regex:
    [0-9]{3,}
  • Matches:
    012
    1234
    555
    98754378623
  • Doesn't Match:
    10
    7