Administrator’s Guide for SIP-T4X IP Phones28Regular expression, often called a pattern, is an expression that specifies a set of strings.A regular expression provides a concise and flexible means to “match” (specify andrecognize) strings of text, such as particular characters, words, or patterns of characters.Regular expression is used by many text editors, utilities, and programming languagesto search and manipulate text based on patterns.Regular expression can be used to define IP phone dial plan. Dial plan is a string ofcharacters that governs the way for IP phones to process the inputs received from the IPphone’s keypads. IP phones support the following dial plan features: Replace Rule Dial-now Area Code Block OutYou need to know the following basic regular expression syntax when creating dialplan:.The dot “.” can be used as a placeholder or multiple placeholders forany string. Example:“12.” would match “123”, “1234”, “12345”, “12abc”, etc.xThe “x” can be used as a placeholder for any character. Example:“12x” would match “121”, “122”, “123”, “12a”, etc.-The dash “-” can be used to match a range of characters within thebrackets. Example:“[5-7]” would match the number “5”, ”6” or ”7”.,The comma “,” can be used as a separator within the bracket.Example:“[2,5,8]” would match the number ”2”, “5” or “8”.[]The square bracket "[]" can be used as a placeholder for a singlecharacter which matches any of a set of characters. Example:"91[5-7]1234" would match “9151234”, “9161234”, “9171234”.()The parenthesis "( )" can be used to group together patterns, forinstance, to logically combine two or more patterns. Example:"([1-9])([2-7])3" would match “923”, “153”, “673”, etc.$The “$” followed by the sequence number of a parenthesis meansthe characters placed in the parenthesis. The sequence numberstands for the corresponding parenthesis. Example:A replace rule configuration, Prefix: "001(xxx)45(xx)", Replace:
