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Nick
Asked: 2012-07-24 09:38:50 +0800 CST

How can I exit a function in powershell

  • 772

I have a function that I know will throw an error. This error is expected, but when it's thrown I want to end the function. I have a Trap section in my script, and I have used both the Return and the Break commands, but they don't do what I want. I have the trap statement both in the Begin {} and the Process {} sections. I am using the command Get-WmiObject, and I have the -ErrorAction set to stop. A sample of the code and their responses are below.

First Example w/ return:

Function Test {
Param {"Some Parameters"}
Begin {"Some beginning stuff"}
process {
    Trap
    {
        Add-Content $($SomeFile) $($ComputerName + "is Not There")
        return
    } #End Trap
    Get-WmiObject Win32_NTLogEvent `
        -ComputerName $ComputerName `
        -Credential $Cred - `
        -ErrorAction Stop
    }#End Process
End {"Some ending things"}
} #End Function

This one simply keeps going on, without exiting the function.

Second Example w/ break:

Function Test {
Param {"Some Parameters"}
Begin {"Some beginning stuff"}
process {
    Trap
    {
        Add-Content $($SomeFile) $($ComputerName + "is Not There")
        Break
    } #End Trap
    Get-WmiObject Win32_NTLogEvent `
        -ComputerName $ComputerName `
        -Credential $Cred - `
        -ErrorAction Stop
    }#End Process
End {"Some ending things"}
} #End Function

This one exits the entire script.

I have looked around, but I can't find anything specific to exiting just a function. There is a lot more going on in the function, including another Get-WmiObject command. I want it to exit the function if the first Get-WmiObject can't contact the computer. I can't use a ping test, because many of the servers block ICMP.

powershell

3 Answers

  1. Best Answer

    The $?varible can be good for catching errors. It contains a boolean for the last executed command. If the command was excuted without errors $? = $true. The $? will be $false when the last executed command errored.

    Create a boolean that gets set each time after the command that errors. Assuming that the command here is get-wmiObject:

    $running = $true
While ($running) {
Get-WmiObject Win32_NTLogEvent -ComputerName $ComputerName -Credential $Cred
$running = $?
}

    Since you probably have a conditional in your loop already, it would look something like while(<condition> -and $running)

    And if you would like to add your error message in, just throw something after you set running like this

    if(!$running){Add-Content $($SomeFile) $($ComputerName + "is Not There")  }
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  2. Return will in fact not help, but you can use break, the only requirement is to use it as it was designed - to get out of the loop... :)

    Trick here is to build simple loop that will run only once no matter what and use break inside the loop:

    # Script body...

do {
    Test-WithBreak
} until ($true)

# Other operations you want to perform even if Test-WithBreak breaks.

    The reason behind it is the fact, that break is loop directive and in PowerShell it does not care for any limits (so break in script, run from script, run from script will be able to walk all the way up and kill whole thing, unless it find some loop to stop him).

    I blogged about this issue a while ago.

    • 3

  3. Try "Continue" as keyword

    Trap [Exception] { “In PowerShell” }

    • 2