Hands-on Regular Expressions Simple rules for powerful changes

June 27 th - 30 th 2007www.cfunited.com DefinitionsDefinitions String - Any collection of 0 or more characters. Example: “This is a String” SubString - A segment of a String Example: “is a” Case Sensitivity - detection if a character is upper or lower case.

June 27 th - 30 th 2007www.cfunited.com Simple Task Find the word “Name” inside a string: Position=#Find(‘Name’, String)# Position=0

June 27 th - 30 th 2007www.cfunited.com Simple Text Find the word “Name” inside a string: Position=#Find(‘name’, String)# Position=4

June 27 th - 30 th 2007www.cfunited.com Simple Task Find the word “Name” inside a string: Position= #FindNoCase(‘Name’, String)# Position=4

June 27 th - 30 th 2007www.cfunited.com Simple Task Find the word “Name” inside a string using Regular Expressions: Position=#REFindNoCase(‘Name’, String)# Position=4

June 27 th - 30 th 2007www.cfunited.com Intro to Regular Expressions Refereed to as RegEx Matches patterns of characters Used in many languages (ColdFusion, Perl, JavaScript, etc.) Uses a small syntax library to do ‘dynamic’ matches Can be used for Search and/or Replace actions Slightly slower than similar Find() and Replace() functions Has both a case sensitive and a non-case sensitive version of each function operation  REFind()  REFindNoCase()  REReplace()  REReplaceNoCase

June 27 th - 30 th 2007www.cfunited.com RegEx Basics Rule 1: A character matches itself as long as it is not a control character. Example: A=“A” A=“a” (non-case sensitive) Position= #REFindNoCase(‘n’, String)# Position=4

June 27 th - 30 th 2007www.cfunited.com RegEx Basics Rule 1a: A search will return the first successful match. To get a different match, set the start position (third attribute of the function - optional) Position1= #REFindNoCase(‘M’, String)# Position2= #REFindNoCase(‘M’, String, 2)# Position1=1 Position2=12

June 27 th - 30 th 2007www.cfunited.com RegEx Basics Rule 2: A collection of non-control characters matches another collection of non-control characters. AA=“AA” AA!=“Aa” (case sensitive) AA=“Aa” (non-case sensitive) A A=“A A” (notice the space) Position=#REFindNoCase(‘y n’, String)# Position=2

June 27 th - 30 th 2007www.cfunited.com RegEx Basics Rule 3: A period (.) is a control character that matches ANY other character. Example:. = “A” A. = “Ac” A.A=“A A” Position= #REFindNoCase(‘N.me’, String)# Position=4

June 27 th - 30 th 2007www.cfunited.com RegEx Basics Rule 4: A control character can be ‘escaped’ by using a backslash (\) before it. This will cause the control character to match a text version of itself. Example:. = “.” \. = “.” A\.A = “A.A” Position1=#REFindNoCase(‘tz\.’, String)# Position=26

June 27 th - 30 th 2007www.cfunited.com RegEx Anchoring Rule 5a: Using the caret (^) will make sure the text your searching for is at the start of the string. Example: ^A= “A” ^M != “AM” Position1=#REFindNoCase(‘^My’, String)# Position2=#REFindNoCase(‘^is’, String)# Position1=1 Position2=0

June 27 th - 30 th 2007www.cfunited.com RegEx Anchoring Rule 5b: Using the dollar sign ($) will make sure the text your searching for is at the end of the string. Example: A$ = “A” M$ = “MAM” (second M will be returned) Position1=#REFindNoCase(‘\.$’, String)# Position1=28

June 27 th - 30 th 2007www.cfunited.com RegEx Ranges Rule 6: When looking for one of a group of characters, place them inside square brackets ([]). Example: ‘[abc]’ will match either a, b, or c. ‘[.+$^]’ will match either a period (.), a plus (+), a dollar sign ($) or a caret (^). Note that all special characters are escaped within square brackets. Position1=#REFindNoCase(‘M[aeiou]’, String)# Position1=6

June 27 th - 30 th 2007www.cfunited.com RegEx Ranges Rule 7a: A caret (^), when used within square brackets ([]) is has the effect of saying ‘NOT these characters’. It must be the first character for this to work. Example: ‘[^abc]’ will match ANY character other than a, b, or c. Position1=#REFindNoCase(‘M[^aeiou]’, String)# Position1=1

June 27 th - 30 th 2007www.cfunited.com RegEx Ranges Rule 7b: A dash (-), when used within square brackets ([]) has the effect of saying ‘all characters from the first character till the last’. Example: ‘[a-e]’ will match ANY character between a and e. Position1=#REFindNoCase(‘M[a-m]’, String)# Position1=6

June 27 th - 30 th 2007www.cfunited.com RegEx Ranges Rule 8: ColdFusion has a series of pre-built character ranges. These are referenced as [[:range name:]]. Example: [[:digit:]] - same as 0-9 (all numbers) [[:alpha:]] - same as A-Z and a-z (all letters of both case) Position1=#REFindNoCase(‘[[:space:]]’, String)# Position1=3

June 27 th - 30 th 2007www.cfunited.com RegEx Character Classes

June 27 th - 30 th 2007www.cfunited.com RegEx Multipliers Any character or character class can be assigned a multiplier that will define the use of the character or class. These multipliers can say that a character must exist, is optional, may exist for a certain minimum or maximum, etc. Multiplier characters include:  Plus (+)One or more  Asterisk (*)0 or more Question Mark (?) may or may not exist once Curly Brackets({})A specific range of occurances

June 27 th - 30 th 2007www.cfunited.com RegEx Multipliers The Plus (+) multiplier specifies that the character or character group must exist but can exist more than once. Example: A+ - A followed by any number of additional A’s [[:digit:]]+ - A number (0-9) followed by any amount of additional numbers Position1=#REFindNoCase(‘is+i’, String)# Position1=2

June 27 th - 30 th 2007www.cfunited.com RegEx Multipliers The Asterisk (*) multiplier specifies that the character or character group may or may not exist, and can exist more than once. (I.e. 0 or more) Example: A* - Either no A or an A followed by any number of additional A’s [[:digit:]]* - Either no number (0-9) or a number followed by any amount of additional numbers Position1=#REFindNoCase(‘si*s’, String)# Position1=3

June 27 th - 30 th 2007www.cfunited.com RegEx Multipliers The Question mark (?) multiplier specifies that the character or character group may or may not exist, but only once. Example: A? - Either A or no As [[:digit:]]+ - One or no numbers (0-9) Position1=#REFindNoCase(‘p?i’, String)# Position1=2

June 27 th - 30 th 2007www.cfunited.com RegEx Multipliers Curly brackets ({}) can be used to specify a minimum and maximum range for a character to appear. The format is {min, max} Example: A{2,4} - 2 As or more but no more than 4. [[:digit:]]{1,6} - 1 number (0-9) or more, but no more than 6. Position1=#REFindNoCase(‘s{2,3}’, String)# Position1=3

June 27 th - 30 th 2007www.cfunited.com RegEx SubExpressions SubExpressions are a way of grouping characters together. This allows us to reference the entire group at once. To group characters together, place them within parenthesis (). Example: (Name) = name (Name)+ = name, namename or basically one or more names. Position1=#REFindNoCase(‘(iss)+’, String)# Position1=2

June 27 th - 30 th 2007www.cfunited.com RegEx SubExpressions An additional special character that is usable within a subExpression is the pipe (|). This means either the first group of text or the second (or more). Example: (Na|me) = na or me (Name|Date) = Name or date Position1=#REFindNoCase(‘(hard|word)’, String)# Position1=18

June 27 th - 30 th 2007www.cfunited.com RegEx SubExpressions SubExpressions allow us to do something else that’s special; back referencing. This is the ability to reference one or more groups directly. This is done by using the backslash (\) followed by a number that specifies which subexpression we want. Example: (name)\1 = namename (Name|Date)\1 = namename or datedate Position1=#REFindNoCase(‘(is )\1’, String)# Position1=13

June 27 th - 30 th 2007www.cfunited.com REReplaceREReplace The REReplace() and REReplaceNoCase() functions use everything you’ve learned about searching and allows you to ‘work’ with the search results, I.e. replace them with something. Example: Position1=#REReplaceNoCase(String, ‘iss’, ‘emm’)# Position2=#REReplaceNoCase(String, ‘iss’, ‘emm’, ‘all’)# Position1=Memmissippi is a hard word Position2=Memmemmippi is a hard word