PowerShell command or code to know if script execution has been stopped

Use Try/Catch/Finally.

Put whatever code is going to notify you the script exited in the Finally block.

Try this:

Try { while  (1) {$i++} }
Catch{ Write-Host 'Catch block ran' }
Finally{Write-host 'Finally block ran'}

Notice if you abort the script with Ctrl+C the Catch block does not run, but the Finally block does.

The Catch block only runs if there is an error. The Finally block always runs, even if you abort the script with Ctrl+C.

So:

Try {#your script here}
Catch {}
Finally {#Export log file}

And the log file will be exported if the script is aborted during the Try block.

If they hit Ctrl+C while it's exporting, you may still lose some log data.

The best way to ensure you get all the log data is to write the log events to disk as they occur.

Not sure what your real question is. Maybe you could post the code here. You can add

$ErrorActionPreference = 'Stop'

at the start of your script, that will stop the script when an error is encountered.

Try using Try/Catch statement for proper error handling.

http://blogs.technet.com/b/heyscriptingguy/archive/2010/03/11/hey-scripting-guy-march-11-2010.aspx

There are similar questions here on SO like this one, but the only way to retain the information in the CSV is to write the file to disk as your script is executing.

Doing this should be fast, but in case it is not, your script does not have to write the file every time there is more data. It can queue up data and write to disk after some count of data is in the queue and/or time has elapsed (I usually do both).