Regular expressions

Recommendations

Examples

In Entuity, attributes values in which you can free type also allow entry of regular expressions (Regex). When defining filter rules with regular expression, note that pattern matching is case-sensitive.

Recommendations:

• It is unnecessary and expensive to include .* at the beginning or end.
  Instead of .*Et0/1/0.* use Et0/1/0
  
  
  
  
• It is also expensive to use capturing groups.
  (<text-to-match) is a capturing group, (?:<text-to-match) is a non-capturing group.
  
  
• Case insensitive matches should be avoided - these are expensive due to the need to support multiple character sets.
  Therefore, do not use (?i) or /i unless it is unavoidable (and if so, use it for the smallest part of the search).

Examples:

• a name that includes lon:
  

  lon

• a name that starts with lon:
  

  ^lon

• a name that starts with either lon or par:
  

  /^(?:(?:lon)|(?:par))

• a name that ends in 1:
  

  1$

• a name that ends in a, b or c:
  

  [abc]$

• a name that contains at least one digit:
  

  [0-9]

• a name that include s, t, u or v:
  

  [!s-v]

• a name that include a pair of digits next to each other:
  

  [0-9]{2}

• a name that has x as the fourth character:
  

  ^…x

• 1 or more special characters (metacharacters) in their name require that the character is escaped. For example,  a name with a plus sign is escaped using the backslash:
  

  eol\+us