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How do I negate a condition in PowerShell?


Question

How do I negate a conditional test in PowerShell?

For example, if I want to check for the directory C:\Code, I can run:

if (Test-Path C:\Code){
  write "it exists!"
}

Is there a way to negate that condition, e.g. (non-working):

if (Not (Test-Path C:\Code)){
  write "it doesn't exist!"
}

Workaround:

if (Test-Path C:\Code){
}
else {
  write "it doesn't exist"
}

This works fine, but I'd prefer something inline.

2017/05/28
1
278
5/28/2017 10:22:37 PM

Accepted Answer

You almost had it with Not. It should be:

if (-Not (Test-Path C:\Code)) {
    write "it doesn't exist!"
} 

You can also use !: if (!(Test-Path C:\Code)){}

Just for fun, you could also use bitwise exclusive or, though it's not the most readable/understandable method.

if ((test-path C:\code) -bxor 1) {write "it doesn't exist!"}
2014/05/19
523
5/19/2014 11:56:34 PM

If you are like me and dislike the double parenthesis, you can use a function

function not ($cm, $pm) {
  if (& $cm $pm) {0} else {1}
}

if (not Test-Path C:\Code) {'it does not exist!'}

Example

2014/08/18

Powershell also accept the C/C++/C* not operator

if ( !(Test-Path C:\Code) ){ write "it doesn't exist!" }

I use it often because I'm used to C*...
allows code compression/simplification...
I also find it more elegant...

2019/09/13

if you don't like the double brackets or you don't want to write a function, you can just use a variable.

$path = Test-Path C:\Code
if (!$path) {
    write "it doesn't exist!"
}

Source: https://stackoverflow.com/questions/8095638
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