Launch Applications in WIndows using AppID and get the pid

Question

I'm trying to launch Windows applications using their AppID such as Microsoft.WindowsCalculator_8wekyb3d8bbwe!App which I get by calling Get-StartApps

Currently I can launch the applications but can't get the correct PID

cmd = exec.Command("powershell", "start", `shell:AppsFolder\Microsoft.WindowsCalculator_8wekyb3d8bbwe!App`)
err := cmd.Start()
fmt.Println(cmd.Process.Pid)

This returns the PID of powershell

C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe start shell:AppsFolder\Microsoft.WindowsCalculator_8wekyb3d8bbwe!App

Is there a way to launch the application by the AppID and still get the correct PID?

Answer 1

tl;dr

// Make PowerShell not only launch Calculator, but also
// determine and output its PID, as described in the next section.
out, _ := 
        exec.Command(
          `powershell.exe`, 
          `-NoProfile`, 
          `-Command`, 
          `Start-Process -ErrorAction Stop calculator: ; (Get-Process Calculator | Where-Object SessionId -eq (Get-Process -ID $PID).SessionId).ID`,
        ).Output()

// Parse stdout output, which contains the PID, into an int
var pid int
fmt.Sscanf(string(out), "%d\n", &pid)

---

• In principle, you can pass -PassThru to PowerShell's Start-Process (start) cmd, which returns a process-info object that has an .Id property containing the launched process' PID, and output the latter.

• Unfortunately, with UWP / AppX applications specifically, such as Calculator, this does not work, which is a problem that exists in the underlying .NET APIs, up to at least .NET 6.0 - see GitHub issue #10996.

You can try the following workaround:

• Launch the AppX application with Start-Process, which indirectly creates a process whose name is Calculator (Windows 10) / CalculatorApp (Windows 11).

  • You can identify this name yourself if you run (Get-Process *calc*).Name after launching Calculator. Get-Process *calc* | Select-Object Name, Path would show the executable path too, but note that this executable should be considered an implementation detail and can not be invoked directly.

• Return the ID of that Calculator / CalculatorApp process. The fact that Calculator only ever creates one such process in a given user session actually makes identifying that process easy.

  • Note that this means that the PID of a preexisting Calculator process may be returned, which, however, is the correct one, because the transient process launched by Start-Process simply delegates creation of a new Calculator window to an existing process.

  • If you wanted to identify the newly created window, more work would be required: You'd have to enumerate the process' windows and identify the one with the highest z-order.

PowerShell code (note: in Windows 11, replace Calculator with CalculatorApp):

# Launch Calculator - which may reuse an existing instance and
# merely create a new *window* - and report the PID.
Start-Process -ErrorAction Stop calculator:
(Get-Process Calculator | Where-Object SessionId -eq (Get-Process -ID $PID).SessionId).ID

^{Note that I've used the URL scheme calculator: as a simpler way to launch Calculator.}

Note:

• The Where-Object SessionId -eq (Get-Process -ID $PID).SessionId guards against mistakenly considering potential Calculator processes created by other users in their own sessions (Get-Process returns all processes running on the local machine, across all user sessions). Filtering by .SessionID, i.e. by the active user session (window station), prevents this problem.

As a PowerShell CLI call:

powershell.exe -NoProfile -Command "Start-Process -ErrorAction Stop calculator: ; (Get-Process Calculator | Where-Object SessionId -eq (Get-Process -ID $PID).SessionId).ID"