Compare two string variables in PowerShell

Question

I have two variables in sorted order.

$a contains

Gi1/1
Gi1/2

$b contains

Gi1/1
Gi1/2
Gi1/3

I tried to compare two variables whether it is equal or not equal as below:

if($a -eq $b) {
    write-host "equal"
} else {
    write-host "not equal"
}

but it didn't seem to work. The output should be "not equal", but it outputs as "equal". How can I fix this?

How are your $a and $b variables being declared? You haven't provided enough information. — Maximilian Burszley
– Maximilian Burszley, Commented Mar 12, 2018 at 14:20
I agree with @TheIncorrigible1 - you need to update your question so it shows how the two variables are being assigned. (Are you really sure they are String objects, for example?) — Bill_Stewart
– Bill_Stewart, Commented Mar 12, 2018 at 15:18
In the comment to the one answer, he says they're created using Select-String @Bill_Stewart — Maximilian Burszley
– Maximilian Burszley, Commented Mar 12, 2018 at 15:20

Maximilian Burszley · Accepted Answer · 2020-11-20 00:22:55Z

4

What you have are two arrays (being returned from Select-String), but you're trying to do a string comparison. When you do that, it's trying to do:

$a.ToString() == $b.ToString()

which is

"System.Object[]" == "System.Object[]"

A workaround, if the array only contains strings, is to concatenate them equally and then compare:

$a = @('Gi1/1', 'Gi1/2')
$b = @('Gi1/1', 'Gi1/2', 'Gi1/3')

if (($a -join '') -eq ($b -join '')) {
    'Equal'
}
else {
    'Not equal'
}

answered Mar 12, 2018 at 14:32

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