CODEWITHSUNDEEP
regexpowershell
user1411430
user1411430

Reputation: 163

Cast [regex] in PowerShell results in case sensitivity strangeness - why?

I'm new to PowerShell scripting, and I am puzzled by some behaviour I have encountered.

I have been following examples to learn how to use matching and had seen some examples where [regex] was put in front of a string. I had assumed (perhaps wrongly) that this is a cast, explicitly specifying that the object is a regular expression. But it seems that using [regex] changes the case sensitivity of the resulting match:

PS > $array = 'ABC','DEF','GHI'
PS > $array -match 'DEF'
DEF
PS > $array -match 'def'
DEF
PS > $array -match [regex]'def'
PS > $array -match [regex]'DEF'
DEF

What is actually going on, here? What is the [regex] doing, that results in case sensitivity?

Upvotes: 0

Views: 1683

Answers (3)

Nvlddmkm
Nvlddmkm

Reputation: 31

Because I don't have enough reputation to comment to add to @Ansgar Wiechers answer, I will answer here to also note if you want to ignore case when casting [regex] from .NET, you can prefix your pattern with (?i) which is a mode modifier (case insensitivity). Here is a good resource where you can check out the available mode modifiers (there's a lot).

So, PS > $array -match [regex]'(?i)def' would return true.

Upvotes: 0

Ansgar Wiechers
Ansgar Wiechers

Reputation: 200463

[regex]'def' is casting the string to a Regex object, which is case-sensitive by default. PowerShell regular expressions on the other hand are case-insensitive by default.

PS C:\> ('def').GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     String                                   System.Object


PS C:\> ([regex]'def').GetType()

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     Regex                                    System.Object

Upvotes: 3

Andrew Cheong
Andrew Cheong

Reputation: 30293

The $array -match calls are case-insensitive by default.

Adding the [regex] keyword initiates a regular expressions search, and regular expressions are by default case-sensitive. That's all.

Upvotes: 1

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