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windowspowershelllogical-operators

Unable to use logical operator while comparing strings for input validation in Powershell

I am attempting to prompt a user for input and then validate if the users input matches one of two different options, and will exit if a correct input was not given.

In the example, I am asking the user to enter 'BOB' or 'TOM' as valid inputs, however when I run this code I will always get the message 'Server type not entered correctly', even when I enter BOB as an input for the prompt.

$ServerType = Read-Host -Prompt 'Enter Server Type (BOB or TOM)'

If ($ServerType -ne  "BOB" -Or $ServerType -ne  "TOM")
{
Write-Host -NoNewLine 'Server type not entered correctly'
}

I have also tried

If (($ServerType -ne  "BOB") -or ($ServerType -ne  "TOM"))
{
Write-Host -NoNewLine 'Server type not entered correctly'
}

However, when I only test for one value it works:

If ($ServerType -ne  "BOB")
{
Write-Host -NoNewLine 'Server type not entered correctly'
}

Any ideas why I might be getting this?

Solution

  • As in my comment, the logical operator in this case should be -and but allow me to give you 2 examples where your validation could be improved.

    • First one is using the -match \ -notmatch comparison operators, which allows the use of regex:
    $ServerType = Read-Host -Prompt 'Enter Server Type (BOB or TOM)'

if($ServerType -notmatch '^(bob|tom)$')
{
    Write-Host -NoNewLine 'Server type not entered correctly'
}

    try
{
    [validateset('bob','tom')]
    $ServerType = Read-Host -Prompt 'Enter Server Type (BOB or TOM)'
}
catch
{
    Write-Host -NoNewLine 'Server type not entered correctly'
}