How to stop power shell script on error? - bash

Question

I have bellow script
$ErrorActionPreference = "Stop";
while($true) {
try {
Write-Host "Step 1";
Dir C:\arts #Error
Write-Host "Step 2";
exit 0
break;
}
catch {
"Error in " + $_.InvocationInfo.ScriptName + " at line: " + $_.InvocationInfo.ScriptLineNumber + ", offset: " + $_.InvocationInfo.OffsetInLine + ".";
$Error
exit 1
break;
}
}
It stops on Dir C:\arts line and that is good for me. As I understood it happens cos I have line $ErrorActionPreference = "Stop"; at the beginning.
I also have some docker params
Param(
[Parameter(Mandatory=$True,ParameterSetName="Compose")]
[switch]$Compose,
[Parameter(Mandatory=$True,ParameterSetName="ComposeForDebug")]
[switch]$ComposeForDebug,
[Parameter(Mandatory=$True,ParameterSetName="StartDebugging")]
[switch]$StartDebugging,
[Parameter(Mandatory=$True,ParameterSetName="Build")]
[switch]$Build,
[Parameter(Mandatory=$True,ParameterSetName="Clean")]
[switch]$Clean,
[parameter(ParameterSetName="Compose")]
[Parameter(ParameterSetName="ComposeForDebug")]
[parameter(ParameterSetName="Build")]
[parameter(ParameterSetName="Clean")]
[ValidateNotNullOrEmpty()]
[String]$Environment = "Debug"
)
If I put $ErrorActionPreference = "Stop" line before docker params I will have error Cannot convert value "System.String" to type "System.Management.Automation.SwitchParameter". Boolean parameters accept only Boolean values and numbers, such as $True, $False, 1 or 0.
In case if I put $ErrorActionPreference = "Stop"; line after docker params, script is continued to run and that is not that I want.
I do not know what I need to do here, so I will be grateful for any help

Answer 1

$ErrorActionPreference doesn't work with command line utilities like docker as they don't throw exceptions in PowerShell. You would have to use returncode/errorlevel or parse the output to handle those type of errors. Useful automatic variables:
$?
Contains the execution status of the last operation. It contains
TRUE if the last operation succeeded and FALSE if it failed.
$LastExitCode
Contains the exit code of the last Windows-based program that was run. Same as %errorlevel% in cmd.
If you detect an error, you can throw an exception to stop the script or use something like exit to stop the script. Example:
function Test-Error {
$ErrorActionPreference = "Stop"
Write-Host Before
ping -n 1 123.123.123.123
#If last command was not successfull.
#You can also have checked $lastexitcode, output etc.
if($? -eq $false) {
#Throw terminating error
#throw "Error"
#Or since we've chosen to stop on non-terminating errors, we could use:
Write-Error -ErrorId $LASTEXITCODE -Message "Ping failed"
}
Write-Host After
}
Test-Error
Output:
Before
Pinging 123.123.123.123 with 32 bytes of data:
Request timed out.
Ping statistics for 123.123.123.123:
Packets: Sent = 1, Received = 0, Lost = 1 (100% loss),
Test-Error : Ping failed
At line:22 char:1
+ Test-Error
+ ~~~~~~~~~~
+ CategoryInfo : NotSpecified: (:) [Write-Error], WriteErrorException
+ FullyQualifiedErrorId : 1,Test-Error
If you're creating a advanced function, you could set the default ErrorAction for the scope of the cmdlet like this:
function Test-Error {
[CmdLetBinding()]
param(
$Name = "World"
)
#If -ErrorAction is not specified by the user, use Stop for the scope of the function
if(-not $MyInvocation.BoundParameters.ContainsKey("ErrorAction")) { $ErrorActionPreference = "Stop" }
"Hello $Name ! My ErrorAction is: $ErrorActionPreference"
}
PS > $ErrorActionPreference
Continue
PS > Test-Error -ErrorAction Ignore
Hello World ! My ErrorAction is: Ignore
PS > Test-Error
Hello World ! My ErrorAction is: Stop