Use powershell to interact with active process; send commands

Question

The code below works to interact with a process (send commands to) so long as the powershell session stays active. What I am looking to do is be able to send commands to the active process without powershell staying active. How can I?

The reasoning here Is I want powershell to start a process at a certain time, and then using task scheduler, send a command to be executed within the process at a set time.

Like I said the below works but the powershell session must stay active.

$psi = New-Object System.Diagnostics.ProcessStartInfo;

$psi.FileName = "cmd.exe"; #process file

$psi.UseShellExecute = $false; #start the process from it's own executable file

$psi.RedirectStandardInput = $true; #enable the process to read from standard input

$p = [System.Diagnostics.Process]::Start($psi);

$p.StandardInput.WriteLine("dir")

Answer 1

Based on my experiences, this is not possible with standard input redirection alone once the original PowerShell session has exited. Once PowerShell exits, the $p.StandardInput object is gone, and there's no built-in way to "reconnect" to that pipe from another session. But I have alternative options for you about that :

1. Option 1: Use a Script File or Command Queue

Instead of sending commands interactively via standard input, design your process to read commands from a file or queue at intervals.

• Start cmd.exe with a loop to run commands from a file:

:loop
for /f "usebackq delims=" %%a in ("C:\Temp\command.txt") do (
    if not "%%a"=="" (
        %%a
    )
)
timeout /t 5 >nul
goto loop

• Save that as C:\Temp\cmd-loop.bat, and run it via PowerShell or Task Scheduler:

Start-Process -FilePath "cmd.exe" -ArgumentList "/c C:\Temp\cmd-loop.bat"

• Later, you write a command to the file from a PowerShell scheduled task:

Add-Content -Path "C:\Temp\command.txt" -Value "dir C:\`r`n"

=> This works because the process is reading and executing whatever shows up in command.txt.

2. Option 2: Use a Named Pipe, Socket, or External Listener

This involves more advanced inter-process communication (IPC), such as:

• Having the process listen on a named pipe or TCP port.
• PowerShell can then connect and send data at any time.

=> If you’re comfortable with C#, Node.js, or PowerShell remoting, this opens up many possibilities, but it's more involved.

3. Option 3: Scheduled Tasks Write to the Process via a Custom Interface

If the process you're running supports some kind of command server, like a CLI interface over TCP or pipe, then you can have it wait for commands.

For example, you could:

• Use ncat or socat to run a process that listens on a port.
• Schedule PowerShell tasks to connect and send commands.