PowerShell: Test Equality

-eq operator

value1 -eq value2

return $true if value1 equals to value2. Case-Insensitive.

3 -eq 3
# True

"a" -eq "A"
# True

collection -eq value

filter collection, return items that is equal to value. Case-Insensitive.

Using -eq to Filter Array

If the left side of -eq is array, it'll return a array with elements that compares True.

# using -eq as array filter
3,4,5 -eq 3
# return 3

3,4,5 -eq 6
# return empty array

"cat", "dog", "bird" -eq "dog"
# return "dog"

# the array must be on the left side
3 -eq 3,4,5
# return False

-ieq

Same as -eq

-ceq

Case-sensitive version of -eq

"a" -ceq "A"
# False

-eq is Not Symmetric. (Order Matters)

PowerShell equality operator is not symmetric (nor Reflexive). That is, order matters. x -eq y and y -eq x may return different results, if x and y are not both numbers or string.

• When left-hand-side is a scalar (number or string or $null), -eq return true if right-hand-side is a exact match, else false.
• When left-hand-side is a array, -eq acts as a filter.

For example:

$x = 3,4,5
$y = 3

$x -eq $y
# return 3

$y -eq $x
# return False

Test for $null

To test for $null, always put $null on left-hand-side.

$x = 1,2,3

$null -eq $x
# return False

$x -eq $null
# return empty array

-ne operator (Test not equal)

-ne

negation of -eq

-ine

negation of -ieq

"a" -ine "A"
# False

-cne

negation of -ceq

"a" -cne "A"
# True