Why does AWS Tools for Powershell ignore -ErrorAction SilentlyContinue?

Question

I want to get $null from the Get-IAMUser command in case the user does not exist.

I investigated using -ErrorAction SilentlyContinue but it seems to be ignored.

Line |
   3 |  if ($null -ne (Get-IAMUser -UserName SomeUserName))
     |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | The user with name SomeUserName cannot be found.

Is there a way to get rid of this error message?

Answer 1

Unfortunately, AWS Powershell modules heavily use terminating errors instead of non-terminating errors.

If they used non-terminating errors, we'd be able to use -ErrorAction SilentlyContinue to suppress the error message and continue with executing the script. However, passing -ErrorAction SilentlyContinue to AWS Powershell cmdlets usually has no effect and is 'ignored'.

The error is a terminating error so use try-catch instead.

---

Recommended approach:

$userName = 'random-string'

try {
    $iamUser = Get-IAMUser -UserName $userName
    Write-Host "User '$userName' exists."
} catch {
    Write-Host "User '$userName' does not exist."
}

Alternatively, if you want to really use if ($null -ne $iamUser):

$userName = 'random-string'

try {
    $iamUser = Get-IAMUser -UserName $userName
} catch {
    # will re-throw the exception if it does not relate to the "user not found" scenario
    if ($_.Exception.InnerException.ErrorCode -eq "NoSuchEntity") {
        $iamUser = $null
    } else {
        throw
    }
}

if ($null -ne $iamUser) {
    Write-Host "User '$userName' exists."
} else {
    Write-Host "User '$userName' does not exist."
}

Output:

User 'random-string' does not exist.

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Note that most PowerShell Get-* commands don't throw terminating errors, and so there is currently an open feature request that hopefully is addressed in a future update...