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  • When: 19 Aug 2011 7:00 PM
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  • When: 29 Jun 2013 12:10 AM
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Wiki  >  TechNet Articles  >  PowerShell: Working With Regular Expressions (regex)

PowerShell: Working With Regular Expressions (regex)

PowerShell: Working With Regular Expressions (regex)

Link to Parent: PowerShell - Deep Dive and Best Practice

There are several different ways to work with regular expressions in PowerShell and this wiki will go over some of these different methods. This wiki WILL NOT go in to regex patterns, there are many resources on the web for that. If you need help with patterns check out the resource section.

**This wiki assumes basic regex knowledge**
    If you need help with building RegEx patterns see the Regular Expression Resources below.

Table of Contents


 

PowerShell Regex based operators


There are several different operators that support the use of regex in them. For the most part they are fairly straight forward so this will be a quick run down on how to use each and any neat features they might have.

Case Sensitive Matching


Each PowerShell Operator has a case sensitive version, prefixing any operator with c will make it case sensitive. They can also be prefixed with i to denote insensitive but that is the default option. Some people use it for cleaner more descriptive code. This works with all comparison operators, not just regex based operators.
"Hello Justin" -match "justin"    #true, default is insensitive
"Hello Justin" -cmatch "justin"  #false, case does not match
"Hello Justin" -imatch "justin"   #true, explicit case insensitivity

Match

The PowerShell Match operator will return a True or False value depending on if the source matches the provided pattern. Great for use with Where or If statements.

"The number 7 is great!" -Match "\d"

There is an automatic variable created upon a match called $Matches

"Hello Justin, Welcome" -match "hello\s(\w+), welcome"
"My name is $($matches[1])"

The $Matches variable is a collection of match results from the pattern. Index 0 is the string that was matched and after that its the match group which is anything with in ( )

Replace


detail the use of -replace
String -Replace <regex pattern>[, <replacement string>]

Simple Replace - This is NOT a case sensitive match.
"hello world" -replace "world", "World"

Simple Remove
"hello world" -replace "world"

Regex Replace
"today is 04/13/1999" -replace "\d{2}/\d{2}/\d{4}", (get-date -f "MM/dd/yyyy")

Regex Replace Using Found matches

"justin.rich@technet.com" -replace "^(\w+)\.(\w+)@", '$1-$2@'

 Regex replace using found matches next to numbers

"jrich532" -replace "(\d)\d{2}", "`${1}23"

Split/Join


detail use of -split and -join and how they different from strings .split and .join

Switch Statement


detail the use of regex with the switch statement

Using the .NET regex namespace


There is a type accelerator for the .net regular expression name space [regex]

Performance Considerations

Depending on what sort of matching you need to do, there can be a very significant difference in the performance of regex. Patterns themselves can have an impact on the speed as well.

Resources


List of resources to learn about Regex for PowerShell and to practice.

PowerShell resources

 

Regular Expression  Resources

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Wiki - Revision Comment List(Revision Comment)
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Comments
  • 29 Jun 2013 12:10 AM

    Ed Price - MSFT edited Revision 20. Comment: Title edit, per guidelines

  • 16 Apr 2013 3:11 PM

    Richard Mueller edited Revision 19. Comment: Replaced RGB values with color names in HTML to restore colors

  • 30 Mar 2013 6:51 PM

    jrich edited Revision 18. Comment: fixing format

  • 30 Mar 2013 11:46 AM

    jrich edited Revision 17. Comment: updated Replace as well as case sensitivity

  • 16 May 2012 12:25 PM

    jrich edited Revision 12. Comment: replace documented

  • 19 Feb 2012 5:19 AM

    Craig Lussier edited Revision 6. Comment: added en-us to tags and title

  • 12 Dec 2011 10:17 PM

    Ed Price - MSFT edited Revision 5. Comment: Minor edit on "PowerShell" casing.

Page 1 of 1 (7 items)
Wikis - Comment List
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Comments
  • Posted by
    on 14 Oct 2011 2:31 PM

    Nice set of resources learning regular expression for powershell.

  • Posted by
    on 7 Dec 2011 8:08 AM

    Useful resources.

  • Posted by
    on 12 Dec 2011 10:17 PM

    Ed Price - MSFT edited Revision 5. Comment: Minor edit on "PowerShell" casing.

  • Posted by
    on 19 Feb 2012 5:19 AM

    Craig Lussier edited Revision 6. Comment: added en-us to tags and title

  • Posted by
    on 27 Feb 2012 6:07 AM

    Thanks for sharing :)

  • Posted by
    on 9 Mar 2012 1:53 AM

    I was looking for something like this, thanks for making this wiki Rich

  • Posted by
    on 20 Apr 2012 9:37 AM

    jrich edited Revision 8. Comment: created basic structure, will populate data

  • Posted by
    on 20 Apr 2012 11:39 AM

    jrich edited Revision 10. Comment: updated Match (saving work)

  • Posted by
    on 22 Apr 2012 9:58 PM

    Very useful resources, thanks a lot

  • Posted by
    on 16 May 2012 12:25 PM

    jrich edited Revision 12. Comment: replace documented

  • Posted by
    on 17 Jun 2012 5:54 AM

    joakimbs edited Revision 13. Comment: Promoting my article, since I frankly think it deserves mention here.

  • Posted by
    on 19 Dec 2012 5:49 PM

    Ed Price - MSFT edited Revision 15. Comment: White space tweaks

  • Posted by
    on 30 Mar 2013 11:46 AM

    jrich edited Revision 17. Comment: updated Replace as well as case sensitivity

  • Posted by
    on 30 Mar 2013 6:51 PM

    jrich edited Revision 18. Comment: fixing format

  • Posted by
    on 16 Apr 2013 3:11 PM

    Richard Mueller edited Revision 19. Comment: Replaced RGB values with color names in HTML to restore colors

Page 1 of 2 (16 items) 12