Web service call, if application is running - powershell

Question

I'm looking for a way to execute a web form submittal if an application is running. I'm not sure the best approach, but I did create a PowerShell script that accomplishes what I want.
while($true) {
(Invoke-WebRequest -Method post 'Http://website.com').Content;
Start-Sleep -Seconds 600;
}
Now what I'd like to do is run this only when an application is running and then quit if the application is no longer running. I suspect maybe a Windows service would be the answer? If so, any idea how I could accomplish this?
I had also thought about running this as a Google Chrome extension, but then my googlefu was exhausted. For Chrome, I would just need the script and no need to check on the .exe.
Any thoughts or help would be appreciated. Again, I'm way out of my depth here but have found a need to create something so dummy steps would be much desired.

Answer 1

If you know the name of the process that runs for the application, you can do the following:
$processname = "thing"
# Wait until the process is detected
Do {
Sleep 60
} Until (Get-Process $processName)
# Once it is detected, run the script
# < SCRIPT RUN CODE HERE >
While (1) {
# Monitor the process to make sure it is still running
If (Get-Process $processName) {
Continue
}
Else {
# Stop the script, because the process isn't running.
# < SCRIPT STOP CODE HERE >
# Wait until the process is detected again
Do {
Sleep 60
} Until (Get-Process $processName)
# Once it is detected again, run the script
# < SCRIPT RUN CODE HERE >
}
# You can add in a delay here to slow down the loop
# Sleep 60
}

Answer 2

I think what you're looking for might be WMI eventing. You can register for (and respond to) events that occur within WMI, such as:
When a process starts or stops
When a service starts or stops
When a process exceeds a certain amount of memory usage
When a new version device driver is installed
When a computer is assigned to a new organizational unit
When a user logs on or off
When an environment variables changes
When a laptop battery drops below a certain threshold
Thousands of other cases
To register for WMI events, use the Register-WmiEvent cmdlet. You can use the -Action parameter to declare what PowerShell statements to execute when a matching event is detected. Here is a simple example:
# 1. Start notepad.exe
notepad;
# 2. Register for events when Notepad disappears
# 2a. Declare the WMI event query
$WmiEventQuery = "select * from __InstanceDeletionEvent within 5 where TargetInstance ISA 'Win32_Process' and TargetInstance.Name = 'notepad.exe'";
# 2b. Declare the PowerShell ScriptBlock that will execute when event is matched
$Action = { Write-Host -ForegroundColor Green -Object ('Process stopped! {0}' -f $event.SourceEventArgs.NewEvent.TargetInstance.Name) };
# 2c. Register for WMI events
Register-WmiEvent -Namespace root\cimv2 -Query $WmiEventQuery -Action $Action -SourceIdentifier NotepadStopped;
# 3. Stop notepad.exe
# Note: For some reason, if you terminate the process as part of the same thread, the event
# doesn't seem to fire correctly. So, wrap the Stop-Process command in Start-Job.
Start-Job -ScriptBlock { Stop-Process -Name notepad; };
# 4. Wait for event consumer (action) to fire and clean up the event registration
Start-Sleep -Seconds 6;
Unregister-Event -SourceIdentifier NotepadStopped;
FYI: I developed a PowerShell module called PowerEvents, which is hosted on CodePlex. The module includes the ability to register permanent WMI event subscriptions, and includes a 30+ page PDF document that helps you to understand WMI eventing. You can find this open-source project at: http://powerevents.codeplex.com.
If I were to adapt your code to something that is more practical for you, it might look something like the example below. You could invoke the code on a periodic basis using the Windows Task Scheduler.
# 1. If process is not running, then exit immediately
if (-not (Get-Process -Name notepad)) { throw 'Process is not running!'; return; }
# 2. Register for events when Notepad disappears
# 2a. Declare the WMI event query
$WmiEventQuery = "select * from __InstanceDeletionEvent within 5 where TargetInstance ISA 'Win32_Process' and TargetInstance.Name = 'notepad.exe'";
# 2b. Declare the PowerShell ScriptBlock that will execute when event is matched
# In this case, it simply appends the value of the $event automatic variable to a
# new, global variable named NotepadEvent.
$Action = { $global:NotepadEvent += $event; };
# 2c. Register for WMI events
Register-WmiEvent -Namespace root\cimv2 -Query $WmiEventQuery -Action $Action -SourceIdentifier NotepadStopped;
# 3. Wait indefinitely, or until $global:NotepadEvent variable is NOT $null
while ($true -and -not $global:NotepadEvent) {
Start-Sleep -Seconds 600;
(Invoke-WebRequest -Method post 'Http://website.com').Content;
}