Pass regex options to PowerShell [regex] type

Question

I capture two groups matched using the regexp code below:

[regex]$regex = "^([0-9]{1,20})(b|kb|mb|gb|tb)$"

$matches = $regex.match($minSize)

$size=[int64]$matches.Groups[1].Value
$unit=$matches.Groups[2].Value

My problem is I want to make it case-insensitive, and I do not want to use regex modifiers.

I know you can pass regex options in .NET, but I cannot figure out how to do the same with PowerShell.

Answer 1

After using [regex] type accelerator, Options property is ReadOnly and can't be changed. But you can call a constructor with RegexOptions parameter:

$regex = [System.Text.RegularExpressions.Regex]::new('^([0-9]{1,20})(b|kb|mb|gb|tb)$','IgnoreCase')

To pass multiple options use bitwise or operator on underlying values:

$regex = [regex]::new('^([0-9]{1,20})(b|kb|mb|gb|tb)$',[System.Text.RegularExpressions.RegexOptions]::Multiline.value__ -bor [System.Text.RegularExpressions.RegexOptions]::IgnoreCase.value__)

But simple addition seems to work, too:

[System.Text.RegularExpressions.RegexOptions]::Multiline + System.Text.RegularExpressions.RegexOptions]::IgnoreCase

It would even work when supplied numeric flag (35 = IgnoreCase=1 + MultiLine=2 + IgnorePatternWhitespace=32), altough relying on enum values directly is usually not a best practice:

$regex = [regex]::new('^([0-9]{1,20})(b|kb|mb|gb|tb)$',36)
$regex.Options

Answer 2

Use PowerShell's -match operator instead. By default it is case-insensitive:

$minSize -match '^([0-9]{1,20})(b|kb|mb|gb|tb)$'

For case-sensitive matches, use -cmatch.