A VBScript13

(1)

VBScript

Session 13 Session 13

(2)

?What we learn last session



 What means error handling.What means error handling.



 When to use On EWhen to use On Error statements.rror statements.



 Using the error object.Using the error object.



(3)

Subjects for session 13



 _{Regulal Expressions}_{Regulal Expressions}



 RegExp objectRegExp object 

 _Methods_Methods



 _Properties._Properties.



 _{Using the RegExp object.}_{Using the RegExp object.}



 _{Matches collection object.}_{Matches collection object.}



 _{Match object.}_{Match object.}



 _{SubMatches collection object.}_{SubMatches collection object.}



 _Patterns_Patterns 

 _{Position Matching.}_{Position Matching.}



 Literals.Literals.



 _{Character Classes.}_{Character Classes.}



 Repetition.Repetition.



 _{Alternation & Grouping.}_{Alternation & Grouping.}



(4)

Regular Expression

?What is that



 So what are regular So what are regular expressions? Regularexpressions? Regular expressions provide tools for developing expressions provide tools for developing complex pattern matching and textual complex pattern matching and textual search-and-replace algorithms.

search-and-replace algorithms.



 By creating patterns to match specificBy creating patterns to match specific

strings, a developer has total control over strings, a developer has total control over searching, extracting, or replacing data. searching, extracting, or replacing data.



 In short, to master regular eIn short, to master regular expressions isxpressions is to master your data.

(5)

VBScript RegExp Object



 VBScript Version 5.0 provides regular expressionsVBScript Version 5.0 provides regular expressions

as an object to

as an object to developers.developers.



 In design, the VBScriptIn design, the VBScript RegExpRegExp object is similarobject is similar

to JScript's

to JScript's RegExpRegExp andand StringString objects; in syntaxobjects; in syntax it is consistent with Visual Basic.

it is consistent with Visual Basic.



 _Let_Let_’’_{s describe the object and its properties and}_{s describe the object and its properties and}

methods. methods.



 _{The VBScript}_{The VBScript} _RegExp_RegExp _{object provides 3}_{object provides 3}

properties and 3 methods to

properties and 3 methods to the user.the user.



 _{Methods: Test, Replace, and Execute}_{Methods: Test, Replace, and Execute} 

(6)

RegExp Object

Pettern Property



 A string that is used to define A string that is used to define thethe

regular expression. regular expression.



 This must be set before use of This must be set before use of thethe

regular expression object. regular expression object.



 PatternsPatterns are described in moreare described in more

detail later. detail later.

(7)

RegExp Object

IgnoreCase Property



 A Boolean property that indicates if A Boolean property that indicates if

the regular expression should be the regular expression should be tested against all possible matches tested against all possible matches in a string.

in a string.



 By default, IgnoreCase is set toBy default, IgnoreCase is set to

False. False.

(8)

RegExp Object

Global Property



 GlobalGlobal - A Boolean property that- A Boolean property that

indicates if the regular expression indicates if the regular expression

should be tested against all possible should be tested against all possible matches in a string.

matches in a string.



(9)

RegExp Object

Test Method



 TheThe TestTest method takes a string asmethod takes a string as

its argument and returns True if the its argument and returns True if the regular expression can successfully regular expression can successfully be matched against the string,

be matched against the string, otherwise False is returned.

(10)

RegExp Object

Replace Method



 TheThe ReplaceReplace method takes 2method takes 2

strings as its arguments. strings as its arguments.



 If it is able to successfully matchIf it is able to successfully match

the regular expression in the the regular expression in the search-string

search-string, then , then it replaces thatit replaces that match with the replace-string, and match with the replace-string, and the new string is returned.

the new string is returned.



 If no matches were found, then theIf no matches were found, then the

original search-string is returned. original search-string is returned.

(11)

RegExp Object

Execute Method



 TheThe ExecuteExecute method works likemethod works like

Replace

Replace, except that it returns a, except that it returns a

Matches

Matches collection object,collection object, containing a

containing a MatchMatch object for eachobject for each successful match.

successful match.



(12)

RegExp Object

Using the RegExp object



 _{Here is a sample of a function where demostartes the usage of}_{Here is a sample of a function where demostartes the usage of the}_the

RegExp object. RegExp object. RegExp Function RegExp Function



 _Function_Function _RegExpTest(p_{RegExpTest(patrn,}_{atrn, strng)}_strng)



 _Dim_Dim _{regEx, Match, Matches, str}_{regEx, Match, Matches, str}



 _Set_Set _{regEx =}_{regEx = New}_New _RegExp_RegExp



 _{regEx.Pattern = patrn}_{regEx.Pattern = patrn}



 _{regEx.IgnoreC}_{regEx.IgnoreCase}_{ase =}_{= True}_True



 _{regEx.Global =}_{regEx.Global = True}_True



 _Set_Set _{Matches = regEx.Execute(strng)}_{Matches = regEx.Execute(strng)}



 _For_For _Each_Each _Match_{Match in}_in _Matches_Matches



 _{str = str & "Match found at position}_{str = str & "Match found at position ““}



 _{str = str & Match.FirstIndex & ". Match Value is '"}_{str = str & Match.FirstIndex & ". Match Value is '"}



 _{str = str & Match.Value & "'." &}_{str = str & Match.Value & "'." & vbNewLine}_vbNewLine



 _Next_Next



 _{RegExpTest = str}_{RegExpTest = str}



 _End_End _Function_Function

Line 1 Line 1 Function receives 2 Function receives 2 arguments arguments 1. pattern 1. pattern 2. String to search. 2. String to search. Line 3 Line 3 Creating a new Creating a new RegExp object, RegExp object, assign to assign to RegEx RegEx Line 4 Line 4 Set Pattern Set Pattern Line 5 Line 5 Set case Set case insensitivity insensitivity Line 6 Line 6 Set global Set global applicability applicability Line 7 Line 7 Execute Execute Search Search Line 8 Line 8 Iterate Iterate Matches Matches collection collection.. Line 9-11 Line 9-11

Retieving info from the Retieving info from the result.

(13)

RegExp Object

Matches Collection Object



 TheThe _Matches_Matches collection object is only returned ascollection object is only returned as

a result of the

a result of the ExecuteExecute method.method.



 This collection object can contain zero or moreThis collection object can contain zero or more

Match

Match objects, and the properties of this objectobjects, and the properties of this object are read-only.

are read-only.



 _Count_Count _{- A read-only value that contains the number}_{- A read-only value that contains the number} of

of MatchMatch objects in the collectionobjects in the collection.. 

 _Item_Item _{- A}_{- A read-only value that enables}_{read-only value that enables} _Match_Match objects to be randomly accessed from the

objects to be randomly accessed from the MatchesMatches

collection object. The

collection object. The MatchMatch objects may also beobjects may also be incrementally accessed from the

incrementally accessed from the MatchesMatches collectioncollection object, using a For-Next loop.

(14)

RegExp Object

Match Object



 _{Contained within each}_{Contained within each Matches}_Matches _{collection object are zero or}_{collection object are zero or}

more

more MatchMatch objects.objects.



 These represent each successful match when using These represent each successful match when using regularregular

expressions. expressions.



 _{The properties of these objects are also read-only, and}_{The properties of these objects are also read-only, and}

contain information about each match. contain information about each match.



 _FirstIndex_FirstIndex _{- A}_{- A read-only value that contains the position within}_{read-only value that contains the position within}

the original string where the match occurred. This

the original string where the match occurred. This index uses aindex uses a zero-based offset to record positions, meaning that the first zero-based offset to record positions, meaning that the first position in a string is 0.

position in a string is 0.



 _Length_Length _{- A read-only value that contains the total length of the}_{- A read-only value that contains the total length of the}

matched string. matched string.



 _Value_Value _{- A read-only value that contains the matched value or}_{- A read-only value that contains the matched value or}

text. It is also

(15)

RegExp Object

Submatches Collection Object



 _{Collection of regular expression submatch strings.}_{Collection of regular expression submatch strings.}



 _A_A _SubMatches_SubMatches _{collection contains individual submatch}_{collection contains individual submatch}

strings, and can only be created using the

strings, and can only be created using the ExecuteExecute

method of the

method of the RegExpRegExp object.object. 

 _The_The _SubMatches_SubMatches _{collection's properties are read-only}_{collection's properties are read-only}



 _{When a regular expression is executed, zero or more}_{When a regular expression is executed, zero or more}

submatches can result when subexpressions are submatches can result when subexpressions are enclosed in capturing parentheses.

enclosed in capturing parentheses. 

 _{Each item in the}_{Each item in the} _SubMatches_SubMatches _{collection is the string}_{collection is the string}

found and captured by the regular expression. found and captured by the regular expression.

(16)

Patterns

So What Does a Pattern Look Like?



 Regular expressions are almost another languageRegular expressions are almost another language

by itself. by itself.



 _{VBScript derives its pattern set from Perl,}_{VBScript derives its pattern set from Perl, and its}_{and its}

core features are, therefore, similar to Perl. core features are, therefore, similar to Perl.



 _{These sets of patterns can be broken down into}_{These sets of patterns can be broken down into}

several categories and areas several categories and areas



 _{Position Matching.}_{Position Matching.} 

 _Literals._Literals. 

 Character Classes.Character Classes. 

 _Repetition._Repetition. 

 _{Alternation & Grouping.}_{Alternation & Grouping.} 

(17)

Patterns

Position Matching



 Position matching involves the usePosition matching involves the use

of the ^ and $

of the ^ and $ to search forto search for

beginning or ending of strings. beginning or ending of strings.



 Setting the pattern property toSetting the pattern property to

"^VBScript" will only successfully "^VBScript" will only successfully match "VBScript is cool." But it will match "VBScript is cool." But it will fail to match "I like VBScript."

(18)

Patterns

Position Matching

  ^^ 

 Only match the beginning of a string.Only match the beginning of a string.



 "^A" matches first "A" in "An A+ for"^A" matches first "A" in "An A+ for

Anita. Anita.““..



 $$



 Only match the ending of a string.Only match the ending of a string.



 "t$" matches the last "t" in "A cat in"t$" matches the last "t" in "A cat in

the hat the hat““..

(19)

Patterns

Position Matching

  \b\b 

 Matches any word boundary.Matches any word boundary.



 "ly\b" matches "ly" in "possibly"ly\b" matches "ly" in "possibly

tomorrow. tomorrow.““



 \B\B



(20)

Patterns

Literals.



 Literals can be taken to meanLiterals can be taken to mean

alphanumeric characters, ACSII, octal alphanumeric characters, ACSII, octal characters, hexadecimal characters, characters, hexadecimal characters, UNICODE, or special escaped

UNICODE, or special escaped characters.characters.



 Since some characters have specialSince some characters have special meanings, we must escape them. meanings, we must escape them.



 To match these special characters, weTo match these special characters, we precede them with a "\" in a regular precede them with a "\" in a regular expression

(21)

Patterns

Literals

  _Alphanumeric_Alphanumeric 

 _{Matches alphabetical and}_{Matches alphabetical and numerical characters literally.}_{numerical characters literally.}



 _\n_\n



 _{Matches a new line.}_{Matches a new line.}



 \f \f



 _{Matches a form feed.}_{Matches a form feed.}



 _\r_\r



 _{Matches carriage return.}_{Matches carriage return.}



 _\t_\t



 _{Matches horizontal tab.}_{Matches horizontal tab.}



 _\v_\v



 _{Matches vertical tab.}_{Matches vertical tab.}

  _\?_\?   _{Matches ?}_{Matches ?}   _\*_\*   _{Matches *}_{Matches *}

(22)

Patterns

Literals

  _\+_\+   _{Matches +}_{Matches +}   _\._\.   _{Matches .}_{Matches .}   \|\| 

 _{Matches | (pipe)}_{Matches | (pipe)}

  _\{_\{   _{Matches {}_{Matches {}   _\}_\}   _{Matches }}_{Matches }}   _\\_\\   _{Matches \}_{Matches \}   _\]_\]   _{Matches ]}_{Matches ]}   _\[_\[   _{Matches [}_{Matches [}

(23)

Patterns

Literals

  _$_\(   _{Matches (}_{Matches (}   _$_\)   _{Matches )}_{Matches )}   \xxx\xxx 

 _{Matches the ASCII character expressed by the}_{Matches the ASCII character expressed by the octal number xxx.}_{octal number xxx.}



 _{"\50" matches "(" or chr (40).}_{"\50" matches "(" or chr (40).}



 _\xdd_\xdd



 _{Matches the ASCII character expressed by the hex number dd.}_{Matches the ASCII character expressed by the hex number dd.}



 _{"\x28" matches "(" or chr (40). \}}_{"\x28" matches "(" or chr (40). \}}



 _\uxxxx_\uxxxx



 _{Matches the ASCII character expressed by the}_{Matches the ASCII character expressed by the UNICODE xxxx.}_{UNICODE xxxx.}



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24

Patterns

Character Classes

 _{Character classes enable customized grouping by}

putting expressions within [] braces.

 _{A negated character class may be created by}

placing ^ as the first character inside the [].

 _{Also, a dash can be used to relate a scope of}

characters.

 _{For example, the regular expression}

"[^a-zA-Z0-9]" matches everything except alphanumeric characters.

 _{In addition, some common character sets are}

(25)

Patterns

Character Classes

  _[xyz]_[xyz] 

 _{Match any one character enclosed in}_{Match any one character enclosed in the character set.}_{the character set.}



 _{"[a-e]" matches "b"}_{"[a-e]" matches "b" in "basketball".}_{in "basketball".}



 _[^xyz]_[^xyz]



 _{Match any one character not enclosed in the character set.}_{Match any one character not enclosed in the character set.}



 _{"[^a-e]" matches "s" in "basketball". \xxx}_{"[^a-e]" matches "s" in "basketball". \xxx}



 _..



 _{Match any character except \n.}_{Match any character except \n.}



 _\w_\w



 _{Match any word character.}_{Match any word character.}



 _Equivalen_{Equivalent to}_{t to [a-zA-Z_0-9].}_{[a-zA-Z_0-9].}



 _\d_\d



 _{Match any digit.}_{Match any digit.}



 _Equivalen_{Equivalent to}_{t to [0-9].}_[0-9].



 _\D_\D



 _{Match any non-digit.}_{Match any non-digit.}



(26)

Patterns

Character Classes

  \s\s 

 Match any space character.Match any space character.



 Equivalent to [ \t\r\n\v\f].Equivalent to [ \t\r\n\v\f].



 \S\S



 Match any non-space character.Match any non-space character.

Equivalent to [^ \t\r\n\v\f]. Equivalent to [^ \t\r\n\v\f].

(27)

Patterns

Repetition



 Repetition allows multiple searchesRepetition allows multiple searches

on the clause within the regular on the clause within the regular expression.

expression.



 By using repetition matching, weBy using repetition matching, we

can specify the number of times an can specify the number of times an element may be repeated in a

element may be repeated in a regular expression.

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28

Patterns Repetiton

 _{x}

 _{Match exactly x occurrences of a regular expression.}

 _{"\d{5}" matches 5 digits.}

 _{x,}

 _{Match x or more occurrences of a regular expression.}

 _{"\s{2,}" matches at least 2 space characters.}

 _{x,y}

 _{Matches x to y number of occurrences of a regular expression.}

 _{"\d{2,3}" matches at least 2 but no more than 3 digits.}

 _?

 _{Match zero or one occurrences. Equivalent to {0,1}.}

 _{"a\s?b" matches "ab" or "a b".}

 _*

 _{Match zero or more occurrences. Equivalent to {0,}.}

 ₊

(29)

29

Patterns

Alternation and Grouping

 Alternation and grouping is used to

develop more complex regular expressions.

 Using alternation and grouping

techniques can create intricate

clauses within a regular expression, and offer more flexibility and

(30)

Patterns

Alternation and Grouping



 ()()



 Grouping a clause to create a clause.Grouping a clause to create a clause.



 _{May be nested.}_{May be nested.}



 "(ab)?(c)" matches "abc" or "c"."(ab)?(c)" matches "abc" or "c".



 | (pipe)| (pipe)



 Alternation combines clauses into oneAlternation combines clauses into one

regular expression and then matches regular expression and then matches any of the individual clauses.

any of the individual clauses.



 "(ab)|(cd)|(ef)" matches "ab" or "cd" or"(ab)|(cd)|(ef)" matches "ab" or "cd" or

"ef". "ef".

(31)

Patterns

Backreferences



 Backreferences enable theBackreferences enable the

programmer to refer back to a programmer to refer back to a

portion of the regular expression. portion of the regular expression.



 This is done by use of parenthesisThis is done by use of parenthesis

and the backslash (\) character and the backslash (\) character followed by a single digit.

followed by a single digit.



 The first parenthesis clause isThe first parenthesis clause is

referred by \1, the second by \2, referred by \1, the second by \2, etc.

(32)

32

Patterns

Backreferences

 ()\n

 Matches a clause as numbered by the

left parenthesis.

 "(\w+)\s+\1" matches any word that

occurs twice in a row, such as "hubba hubba."

(33)

Lab 13.1



 Write a program to search the Write a program to search the followingfollowing files or directories in C:\WINNT,

files or directories in C:\WINNT, C:\WINNT\System32

C:\WINNT\System32



 Files containing the lettersFiles containing the letters _““aa_”” toto _““pp_”” oror _““ss_”” toto _““tt_””

at least once, lowercase, Or the number 32 in at least once, lowercase, Or the number 32 in the end of the na

the end of the name (no extension).me (no extension).



 _{Files with extension txt, created this}_{Files with extension txt, created this month}_month

name i.e

name i.e ““SeptemberSeptember”” (use DateValue function)(use DateValue function)



(34)

34

Lab 13.2

 We have a button in an application

that behaves as the follow.

 The label on it _“show_”.

 When pressing on it, the label changes

to “hide”

 Which Regular expression will fit to

(35)

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