Execute code if a PowerShell script is terminated

Question

Is it possible to force the execution of some code if a PowerShell script is forcefully terminated? I have tried try..finally and Traps, but they both don't seem to work, at least when I press Ctrl-C from PowerShell ISE.

Basically, I have a Jenkins build that executes a PowerShell script. If for any reason I want to stop the build from within Jenkins, I don't want any subprocess to lock the files, hence keeping my build project in a broken state until an admin manually kill the offending processes (nunit-agent.exe in my case). So I want to be able to force the execution of a code that terminates nunit-agent.exe if this happens.

UPDATE: As @Frode suggested below, I tried to use try..finally:

$sleep = {
  try {
    Write-Output "In the try block of the job."
    Start-Sleep -Seconds 10
  }
  finally {
    Write-Output "In the finally block of the job."
  }
}

try {
  $sleepJob = Start-Job -ScriptBlock $sleep
  Start-Sleep -Seconds 5
}
finally {
  Write-Output "In the finaly block of the script."
  Stop-Job $sleepJob
  Write-Output "Receiving the output from the job:"
  $content = Receive-Job $sleepJob
  Write-Output $content
}

Then when I executed this and broke the process using Ctrl-C, I got no output. I thought that what I should got is:

In the finally block of the script.
Receiving the output from the job:
In the try block of the job.
In the finally block of the job.

Frode F. · Accepted Answer · 2016-02-15 20:42:47Z

4

I use try {} finally {} for this. The finally-block runs when try is done or if you use ctrl+c, so you need to either run commands that are safe to run either way, ex. it doesn't matter if you kill a process that's already dead..

Or you could add a test to see if the last command was a success using $?, ex:

try {
    Write-Host "Working"
    Start-Sleep -Seconds 100

} finally {
    if(-not $?) { Write-Host "Cleanup on aisle 5" }
    Write-Host "Done"
}

Or create your own test (just in case the last command in try failed for some reason):

try {
    $IsDone = $false
    Write-Host "Working"
    Start-Sleep -Seconds 100
    #.....
    $IsDone = $true

} finally {
    if(-not $IsDone) { Write-Host "Cleanup on aisle 5" }
    Write-Host "Done"
}

UPDATE: The finally block will not work for output as the pipeline is stopped on CTRL+C.

Note that pressing CTRL+C stops the pipeline. Objects that are sent to the pipeline will not be displayed as output. Therefore, if you include a statement to be displayed, such as "Finally block has run", it will not be displayed after you press CTRL+C, even if the Finally block ran.

Source: about_Try_Catch_Finally

However, if you save the output from Receive-Job to a global variable like $global:content = Receive-Job $sleepJob you can read it after the finally-block. The variable is normally created in a different local scope and lost after the finally-block.

edited Feb 15, 2016 at 20:42

answered Feb 15, 2016 at 17:02

Frode F.

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4 Comments

Rafid Over a year ago

Thanks @Frode. I tried it but it didn't work. See my edit above.

Rafid Over a year ago

Oh, I see, that makes sense now, and also makes me happy :) So what is the recommended way of communicating with the main process? Basically, from the sub process, I want to say something like build was stopped, hence we are terminating the NUnit tests, so we could tell from Jenkins server what has happened.

Frode F. Over a year ago

Don't see too many options atm. I would write to a log file or use exit-codes. Ex. let your finally block end with exit 1234.

Rafid Over a year ago

Thanks. Yeah, I was thinking of using log files and dump it from the main script.

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