Basic characteristics of regular expressions

Following are notable characteristics of regular expressions as defined on the Citrix ADC appliance:

  • A regular expression always begins with the string “re” followed by a pair of delimiting characters (called delimiters) that enclose the regular expression that you want to use.

For example, re#<regex_pattern># uses the number sign (#) as a delimiter.

  • A regular expression cannot exceed 1499 characters.

  • Digit matching can be done by using the string \d (a backslash followed by d).

  • White space can be represented by using \s (a backslash followed by s).

  • A regular expression can contain white spaces.

Following are the differences between the Citrix ADC syntax and the PCRE syntax:

  • The Citrix ADC does not allow back references in regular expressions.
  • You should not use recursive regular expressions.
  • The dot meta-character also matches the newline character.
  • Unicode is not supported.
  • The operation SET_TEXT_MODE(IGNORECASE) overrides the (?i) internal option in the regular expression.
Basic characteristics of regular expressions