Logical Operators

PowerShell logical operators are used to test or validate an expression. Typically the result of these operations is TRUE or FALSE. Table 6.2 describes the operators:

Table 6.2: PowerShell Logical Operators
Open table as spreadsheet

Operator	Description	Example
-and	All expressions must evaluate as TRUE.	(1 -eq 1) -and (2 - eq 2) returns TRUE
-or	At least one expression must evaluate as TRUE.	(1 -eq 1) -or (2 -eq 4) returns TRUE
-not	Evaluates the inverse of one of the expressions.	(1 -eq 1) -and -not (2 -gt 2) returns TRUE
!	The same as -not.	(1 -eq 1) -and ! (2 -gt 2) returns TRUE

Logical operators should be used when you want to evaluate multiple conditions. While you can evaluate several expressions, your scripts and code will be easier to debug or troubleshoot if you limit the operation to two expressions:

 PS C:\> $varA=5 PS C:\> $varB=5 PS C:\> if (($varA -eq $varB) -and ($varB -gt 20)) >>{ >>Write-Host "Both conditions are true." >>} >>else >>{ >>Write-Host "One or both conditions are false." >>} >> One or both conditions are false. PS C:\> 

Here's the same example using -or:

 PS C:\> if (($varA -eq $varB) -or ($varB -gt 20)) >> { >> Write-Host "At least one condition is true." >> } >> else >> { >> Write-Host "Both conditions are false." >> } At least one condition is true. PS C:\> 

We get a different result if we change $varA to 20:

 PS C:\> $varA=20 PS C:\> if (($varA -eq $varB) -or ($varB -gt 20)) >> { >> Write-Host "At least one condition is true." >> } >> else >> { >> Write-Host "Both conditions are false." >> } >> Both conditions are false. PS C:\>