How to loop in powershell until successful?

The special variable $lastexitcode gives you the exit code of the last native executable (i.e. not cmdlet) that was run. This will have different values depending on the results of the operation. For example, it will be 5 if appcmd encounters access denied. It should be 0 if the last command completed successfuolly.

Make sure you check this variable immediately after you run appcmd and in the same script. If not, you risk getting the exitcode from powershell.exe and not from appcmd.exe

I realize that the original issue has likely longs been resolved, but for the sake of Googlers hitting this question, I wrote a general purpose (advanced) function for retrying shell (cmd) commands. In addition to $LASTEXITCODE it can also parse the error stream (with some tools, the exit code can be a lie).

function Call-CommandWithRetries{ [CmdletBinding()] param(      [Parameter(Mandatory=$True)]     [string]$Command,     [Array]$Arguments,     [bool]$TrustExitCode = $True,     [int]$RetrySleepSeconds = 10,     [int]$MaxAttempts = 10,     [bool]$PrintCommand = $True ) Process {  $attempt = 0  while ($true)  {      Write-Host $(if ($PrintCommand) {"Executing: $Command $Arguments"} else {"Executing command..."})    & $Command $Arguments 2>&1 | tee -Variable output | Write-Host   $stderr = $output | where { $_ -is [System.Management.Automation.ErrorRecord] }   if ( ($LASTEXITCODE -eq 0) -and ($TrustExitCode -or !($stderr)) )   {    Write-Host "Command executed successfully"    return $output   }   Write-Host "Command failed with exit code ($LASTEXITCODE) and stderr: $stderr" -ForegroundColor Yellow   if ($attempt -eq $MaxAttempts)   {    $ex = new-object System.Management.Automation.CmdletInvocationException "All retry attempts exhausted"    $category = [System.Management.Automation.ErrorCategory]::LimitsExceeded    $errRecord = new-object System.Management.Automation.ErrorRecord $ex, "CommandFailed", $category, $Command    $psCmdlet.WriteError($errRecord)    return $output   }   $attempt++;   Write-Host "Retrying test execution [#$attempt/$MaxAttempts] in $RetrySleepSeconds seconds..."   Start-Sleep -s $RetrySleepSeconds  } }}

For more information (including full documentation) see https://www.ohadsoft.com/2016/04/invoking-arbitrary-shell-cmd-commands-in-powershell.

In your case you would do something like

$appCmd = [io.path]::combine($env:WINDIR, 'system32', 'inetsrv', 'appcmd.exe')$appCmdArg = @('set', 'site', '/site.name:"WebRole_IN_0_CB"', '/[Path=''/''].applicationPool:"ASP.NET v4.0"')$output = Call-CommandWithRetries $appCmd $appCmdArgs# write $output to log etc