Regex Object

When you use the -match operator, even with a regular expression pattern, the operation only returns the first match found:

 PS C:\> $var="Sapien Press PowerShell TFM" PS C:\> $var -match "\w+" True PS C:\> $matches Name                           Value ----                           ----- 0                              Sapien PS C:\> 

To match all instances of the pattern, you need to use the Regex object. In this example, notice that the match method returns all matches in $var:

 PS C:\> $regex=[regex]"\w+" PS C:\> $regex.matches($var) Groups   : {Sapien} Success  : True Captures : {Sapien} Index    : 0 Length   : 6 Value    : Sapien Groups   : {Press} Success  : True Captures : {Press} Index    : 7 Length   : 5 Value    : Press Groups   : {PowerShell} Success  : True Captures : {PowerShell} Index    : 13 Length   : 10 Value    : PowerShell Groups   : {TFM} Success  : True Captures : {TFM} Index    : 24 Length   : 3 Value    : TFM PS C:\> 

We create an object variable called $regex and cast it to a regex object specifying the regular expression pattern. We can now call the matches method of the regex object using $var as a parameter. The method returns all instances where the pattern matches, as well as where they were found in $var.

A more direct way to see all the matches is to use the Value property:

 PS C:\> foreach ($i in $regex.matches($var)) {$i.value} Sapien Press PowerShell TFM PS C:\> 

The results of $regex.matches($var) is a collection. Using a ForEach loop we can enumerate the collection and display the Value property for each item in the collection.

This object has several methods and properties with which you will want to become familiar:

 PS C:\> $regex|get-member    TypeName: System.Text.RegularExpressions.Regex Name                MemberType Definition ----                ---------- ---------- Equals              Method     System.Boolean Equals(Object obj) get_Options         Method     System.Text.RegularExpressions.RegexOpt get_RightToLeft     Method     System.Boolean get_RightToLeft() GetGroupNames       Method     System.String[] GetGroupNames() GetGroupNumbers     Method     System.Int32[] GetGroupNumbers() GetHashCode         Method     System.Int32 GetHashCode() GetType             Method     System.Type GetType() GroupNameFromNumber Method     System.String GroupNameFromNumber(Int32 GroupNumberFromName Method     System.Int32 GroupNumberFromName(String IsMatch             Method     System.Boolean IsMatch(String input), S Match               Method     System.Text.RegularExpressions.Match Ma Matches             Method     System.Text.RegularExpressions.MatchCol Replace             Method     System.String Replace(String input, Str Split               Method     System.String[] Split(String input), Sy ToString            Method     System.String ToString() Options             Property   System.Text.RegularExpressions.RegexOpt RightToLeft         Property   System.Boolean RightToLeft {get;} PS C:\> 

In order to see what the current value of $regex is, we need to use the ToString() method:

 PS C:\> $regex.ToString() \w+ PC C:\> 

IsMatch will return either TRUE or FALSE if any match is made:

 PS C:\> if ($regex.IsMatch($var)) { >> write-host "found" ($regex.Matches($var)).Count "matches" >> } >> found 4 matches PS C:\> 

In this example we check to see if IsMatch is TRUE. If it is TRUE, the number of matches found in the string will be displayed. By the way, the Count method is not a property of the $regex object, but the result of evaluating $regex.Matches($var), which returns a collection object:

 PS C:\> ($regex.Matches($var)).gettype() IsPublic IsSerial Name                                     BaseType -------- -------- ----                                     -------- True     True     MatchCollection                        System.Object PS C:\>