Logical Operators in PowerShell

Logical operators can convert various conditions into a single condition.

This article will discuss real-world examples and apply logical operators in script with PowerShell.

PowerShell Logical Operators

Logical operators are and, or, xor, and not or !.

the -and Operator in PowerShell

The output is true if $a and $b are true; otherwise, false.

Truth Table:

$a = 0
$b = 0
$a -and $b # false (if both variables are false)

$a = 1
$b = 0
$a -and $b  # false (if any of the variables are false)

$a = 1
$b = 1
$a -and $b # true (if both variables are true)

The -and operator returns true only when both are true. In general, the -and operators are used where we want all conditions to be checked and fulfilled.

Here is an example of both conditions that need to be fulfilled.

$attendance = 102
$paid = "Y"
if ($attendance -gt 100 -and $paid -eq "Y") {
    Write-Output "Allow for examination."
}

Output:

Allow for examination.

the -or Operator in PowerShell

The output is false if $a and $b is false, compared to the -and operator.

The -or operator only needs one variable to be true to output true.

Truth Table:

$a = 0
$b = 0
$a -or $b # false (if both conditions are false)

$a = 1
$b = 0
$a -or $b # true (if any of the variables are true)

$a = 1
$b = 1
$a -or $b  # true (if both of the variables are true)

The -or operator returns false only when both conditions are false. In general, the -or operators are used when considering any conditions as true.

$attendance = 99
$marks = 201
if ($attendance -gt 100 -or $marks -gt 200) {
    Write-Output "Give five extra marks."
}

Output:

Give five extra marks.

the -xor Operator in PowerShell

The exclusive or or -xor results from true if only one of $a or $b is true. If both conditions are true, -xor yields a result of false.

Truth Table:

('a' -eq 'A') -xor ('a' -eq 'z') # true as one of them is true
('a' -eq 'A') -xor ('Z' -eq 'z') # false as both of them is true
('a' -eq 's') -xor ('Z' -eq 'p') # false as both of them are false

the -not Operator in PowerShell

The -not operator returns the opposite of the expression output. If the output of the expression is true, the operator will return it as false, and vice-versa.

-not ('a' -eq 'a') # false as the output of expression is true
-not ('v' -eq 'a') # true as output expression is false
-not ('v' -eq 'V') # false as output expression is true
-not ('V' -eq 'V1') # true as output expression is false

The exclamation point ! is the same as the -not operator.

!('a' -eq 'a')  # false as the output of expression is true
!('v' -eq 'a') # true as output expression is false
!('v' -eq 'V') # false as output expression is true
!('V' -eq 'V1') # true as output expression is false