Switch statement with RegEx - having trouble getting a switch statement not to match if string has a dot

Question

Lets say I have switch statement like so:

$NewName = "test.psd"
switch -RegEX ($NewName) {
    "^\..*" { #if string starts with "." it means only change extension
                'Entry Starts with a "."'
        }
   ".*\..*" { # "." is in the middle , change both basename and extension
               'Entry does not start  with a "."'
    }
   "[^.]" { # if no "." at all, it means only change base name
            'No "." present'
    }
}

The first and second condidtions work as expected, but the last one always triggers. It will trigger against:

$NewName = "test.psd"
$NewName = ".psd"
$NewName = "test"

Doesnt regex "[^.]" mean if there is a dot, dont match. Essentially only trigger in the absence of a dot.

My expected outcome is for the last statement to only trigger if there is not dot present.

Any help on this, would be wellcome.

That would only work if `.` were the only character. – js2010 Dec 21 '22 at 20:55 — js2010, Dec 21 '22 at 20:55

score 2 · Accepted Answer · answered Dec 21 '22 at 21:01

2

That would only work if "." were the only character. All the other characters would match it. You would have to repeat that pattern for every character on the line. See also Regex - Does not contain certain Characters

'a.' -match '^[^.]+$'

False


'ab' -match '^[^.]+$'

True

answered Dec 21 '22 at 21:01

js2010

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Aah, I did not know that I was doing it that way, Thanks allot for this and for the explanation – hellen_dorandt89 Dec 21 '22 at 23:08

score 0 · Answer 2 · answered Dec 21 '22 at 20:53

0

The dot is a special character in regular expressions, and needs to be escaped when you want to use a literal dot. Try "[^\.]" for the regular expression in the third case.

answered Dec 21 '22 at 20:53

Jeff Zeitlin

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This isn't actually true inside the square brackets. – js2010 Dec 21 '22 at 21:03

Switch statement with RegEx - having trouble getting a switch statement not to match if string has a dot

2 Answers2