Switch/case statement

Question

I have a function called tabLength that should return a string. This is for formatting in a text document.

Could anyone check out my switch statement and see why I am getting an error on line 6. That is the 'case' that the switch statement is going through.

Function tabLength ( $line ) {
    $lineLength = $line.Length

    switch -regex ( $lineLength ) {
        "[1-4]" { return "`t`t`t" }
        "[5-15]" { return "`t`t" }
        "[16-24]" { return "`t" }
        default { return "`t" }
    }
}

Error Message:

Invalid regular expression pattern: [5-15].
At C:\Users\name\desktop\nslookup.ps1:52 char:11
+         "[5-15]" <<<<  { return "" }
    + CategoryInfo          : InvalidOperation: ([5-15]:String) [], RuntimeException
    + FullyQualifiedErrorId : InvalidRegularExpression

It is only happening to values being sent through [5-15].

Answer 1

[5-15] is not a valid regex character class. You are matching strings, not numbers, so [5-15] essentially says "match a single character from '5' through '1', or '5'" which is not what you want.

If you remove that middle condition, the [16-24] should fail similarly.

Try a switch statement that doesn't use regex, but uses a script block for conditions so you can use a range to test, like this:

Function tabLength ( $line ) {
    $lineLength = $line.Length

    switch ( $lineLength ) {
        { 1..4 -contains $_ } { return "`t`t`t" }
        { 5..15 -contains $_ } { return "`t`t" }
        { 16..24 -contains $_ } { return "`t" }
        default { return "`t" }
    }
}

In powershell 3+, you could use the -in operator and reverse the order:

Function tabLength ( $line ) {
    $lineLength = $line.Length

    switch ( $lineLength ) {
        { $_ -in  1..4 } { return "`t`t`t" }
        { $_ -in 5..15 } { return "`t`t" }
        { $_ -in 16..24 } { return "`t" }
        default { return "`t" }
    }
}