Powershell script ignoring $userInput variable

Question

function processSearch {
Get-Process -Name "$processSearch*"
}

function processKill {
Stop-Process -Name "$processSearch*"
}

$processSearch = Read-Host -Prompt "Enter the full or partial name of the process: "

processSearch

 if ((Get-Process -Name "$processSearch*") -eq $null) {
    Write-Output "ERROR: NO PROCESS FOUND."
    [Threading.Thread]::Sleep(3000) 
 }

if ((Get-Process -Name "$processSearch*") -ne $null) {
    $userInput= Read-Host -Prompt "Kill process?"
} 
     
if ($userInput -eq "y" -or "Y") {
    processKill
}
elseif ($userInput -eq "n" -or "N") {
    Write-Output "Process not killed."   
}
else {
    Write-Output "ERROR: UNHANDLED INPUT."
}

When my script gets to $userInput= Read-Host -Prompt "Kill process?", and I enter any text, the script will terminate the selected process.

I'm new to scripting, so please let me know where my logic is flawed, thank you.

NiMux · Accepted Answer · 2022-06-18 21:56:09Z

4

The issue you're experiencing is because when you're checking the $userInput variable you've forgotten to declare what variable to check against in your -or part of the clause.

This code:

if ($userInput -eq "y" -or "Y") {
    processKill
}
elseif ($userInput -eq "n" -or "N") {
    Write-Output "Process not killed."   
}
else {
    Write-Output "ERROR: UNHANDLED INPUT."
}

should become:

if ($userInput -eq "y" -or $userInput -eq "Y") {
    processKill
}
elseif ($userInput -eq "n" -or $userInput -eq "N") {
    Write-Output "Process not killed."   
}
else {
    Write-Output "ERROR: UNHANDLED INPUT."
}

You could also make the if statements a little less verbose by using the case-sensitive -cin operator as this will check if the value is in an array of given values as below:

if ($userInput -cin "y", "Y") {
    processKill
}
elseif ($userInput -cin "n", "N") {
    Write-Output "Process not killed."   
}
else {
    Write-Output "ERROR: UNHANDLED INPUT."
}

answered Jun 18, 2022 at 21:56

NiMux

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1 Comment

Daniel Over a year ago

Good answer. Just a note, -eq is case-insensitive so the -or part isn't even necessary at all.

mklement0 · Accepted Answer · 2022-06-23 16:21:54Z

NiMux's answer makes good points, but it's worth taking a step back:

PowerShell's operators are case-insensitive by default:
- 'y' -eq 'Y' is $true.
To perform case-sensitive operations, prefix the operator name with c; e.g. -ceq:
- 'Y' -ceq 'Y' is $true, but 'y' -ceq 'Y' is $false.

Therefore:

$userInput -eq 'y' and $userInput -eq 'n' are sufficient in your case.
In case you truly have multiple values to test against, use the -inoperator; e.g.:
- $userInput -in 'y', 'n', 'c'

As for what you tried:

Due to PowerShell's operator precedence,

$userInput -eq "y" -or "Y"

is evaluated as:

($userInput -eq "y") -or ("Y")

That is, the RHS operand of the -or operation is string "Y" alone, and evaluating a non-empty string in PowerShell in a Boolean context always yields $true (irrespective of what the string contains).

In effect, your attempt was therefore equivalent to the following, which is always $true:

($userInput -eq "y") -or $true

The immediate (but suboptimal) fix to your attempt would have been what's shown in NiMux's answer: use of two separate -eq operations ($userInput -eq 'y' -or $userInput -eq 'Y').

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