How do I replace string with the value of another variable in PowerShell

Question

I am attempting to modify the System Path Environment Variable by doing the following. Unfortunately, what I'm observing is that if I hardcode the string it works, but I use a variable (which is what I would prefer to do), it doesn't work.

I get no errors; it just doesn't work. Here's my code:

$GlobalEnvPath = "C:\Path\ToApp\"
$CurrentEnvPath = [System.Environment]::GetEnvironmentVariable('PATH','Machine')
If ($CurrentEnvPath –match ".+?\;$") { $CurrentEnvPath = $CurrentEnvPath –replace ".{1}$" } #Sanitize the acquired string to remove any trailing semi-colons
$TempNewEnvPath = $CurrentEnvPath.Replace("$GlobalEnvPath",$null) #Find and replace the installation directory with a null value
$NewEnvPath = $TempNewEnvPath.Replace(";;",$null) #Find and replace any double semi-colons that may be present
[System.Environment]::SetEnvironmentVariable('PATH',$NewEnvPath,'Machine') #Finally, let’s write our changes back to the system registry

The part I'm having issues with is:

$TempNewEnvPath = $CurrentEnvPath.Replace("$GlobalEnvPath",$null)

Any help would be very much appreciated, thanks.

..are you editing your code in MS Word or something? You have smart quotes all over your snippet. — Maximilian Burszley
– Maximilian Burszley, Commented Apr 11, 2019 at 16:26
Lol, no. I'm coding in the ISE but it's on an airgapped network so I had to retype in a text file. I will edit accordingly. — Kismet Agbasi
– Kismet Agbasi, Commented Apr 11, 2019 at 17:15
It's not clear what actual issue you are having. What is the result you are getting and what are you expecting? — zdan
– zdan, Commented Apr 11, 2019 at 17:22
No need to worry anymore, I have resolved the problem. Turns out I needed to wrap my variable inside a "$()" as such: "$($GlobalEnvPath)" — Kismet Agbasi
– Kismet Agbasi, Commented Apr 11, 2019 at 17:38

Maximilian Burszley · Accepted Answer · 2019-04-11 17:40:22Z

1

Here's my suggested solution:

$path = @([Environment]::GetEnvironmentVariable('PATH', 'Machine') -split ';')

$exclude = [regex]::Escape('C:\Path\ToApp\' -replace '\\$')
$newPath = $path -notmatch $exclude -join ';'

[Environment]::SetEnvironmentVariable('PATH', $newPath, 'Machine')

This removes a lot of room for error. String#Replace is case-sensitive, for example. I also leave the trailing slash absent for that possible edge case.

answered Apr 11, 2019 at 17:40

Maximilian Burszley

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Kismet Agbasi Over a year ago

Hmm, I like your approach as well. Thanks for sharing.

Kismet Agbasi · Accepted Answer · 2019-04-11 17:41:31Z

0

Turns out I needed to wrap my variable inside a $() like so:

$TempNewEnvPath = $CurrentEnvPath.Replace("$($GlobalEnvPath)",$null)

I'm not sure exactly why this is but another colleague of mine brought this to my attention and I thought I'd share it in case someone else ran into this problem. If anyone out there can shed some light on why this is please feel free to do so for our common edification.

If I find additional information as well, I will post back to this answer.

answered Apr 11, 2019 at 17:41

Kismet Agbasi

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1 Comment

Maximilian Burszley Over a year ago

That's actually entire unnecessary. "$var" is equivalent to "$($var)"..

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