How to run a command line from a running application through c#

Miguel Melo

I've searched around and didn't find anything useful! :(

What i want is to have my C# app doing a command to a running process. This running process is a console application and i just need to enter the command "restart".. my try was:

    Process[] processes = Process.GetProcessesByName("OpenSim.32BitLaunch");

    foreach (Process p in processes)
    {
         p.StandardInput.WriteLine("restart");
    }

And i get and exectipon: StandardIn not redirected. I've tried to set RedirectStandardInput but nothing :/

Regards

4 Replies

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Vulpes15y ago
Accepted answer
AFAIK, Sam is correct that you cannot redirect the standard input, output or error streams of a running process unless, of course, you launched it using the Process class in the first place.

However, if the running process is a console application, then what you can do is this:

1. Attach to the console of the running process (if the calling process is itself a console app it needs to free its own console first).

2. Find the window handle of the console you've attached to and force focus onto it.

3. Send the appropriate keys to the console's input stream which the running process can then read.

Here's some code I've figured out to do all that.

Unfortunately, Process.MainWindowHandle is zero and Process.MainWindowTitle is null for a console application so you have to call the API function GetConsoleTitle() to get the window title and then FindWindow() to find the window handle after you've attached to the console. You can then call SetForegroundWindow() to force focus onto it.

If you have control of the running process, it would be better if it could set its own window title to avoid possible ambiguity problems but I've assumed the default title will be unique in the following code.

First build this console application, melo.exe, and set it running, waiting for input:

// melo.cs

using System;

class Test
{
static void Main()
{
string s = Console.ReadLine();
if (s == "restart")
{
Console.WriteLine("OK restarting ....");
}
}
}

Now build this console application, melo2.exe, and set it running in a separate console window:

// melo2.cs

using System;
using System.Diagnostics;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Text;

class Test
{

[DllImport("kernel32.dll")]
static extern uint GetConsoleTitle(StringBuilder lpConsoleTitle, uint nSize);

[DllImport("user32.dll")]
static extern IntPtr FindWindow(IntPtr ZeroOnly, string lpWindowName);

[DllImport("kernel32.dll", SetLastError = true)]
static extern bool AttachConsole(uint dwProcessId);

[DllImport("kernel32")]
static extern bool FreeConsole();

[DllImport("user32.dll")]
static extern bool SetForegroundWindow(IntPtr hWnd);

static void Main()
{
Process[] procs = Process.GetProcessesByName("melo");
if (procs.Length > 0)
{
int pId = procs[0].Id;
FreeConsole();
bool ok = AttachConsole((uint)pId);
if (!ok)
{
int error = Marshal.GetLastWin32Error();
Console.WriteLine(error);
}
else
{
StringBuilder sb = new StringBuilder(256);
GetConsoleTitle(sb, 256u);
IntPtr hWnd = FindWindow(IntPtr.Zero, sb.ToString());
SetForegroundWindow(hWnd);
SendKeys.SendWait("restart{ENTER}");
}
}
}
}

You should see in the first console window, the following output:

restart
OK restarting ....
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Miguel Melo15y ago
Hi guys,

Many thanks for your help! Thanks to you i've been able to solve it :)

Mu solution was made using SetForegroundWindow and SendKeys like sugested (Note that i've already imported the DLL's that Vulpes mentioned):

System.Diagnostics.Process process = Process.GetProcessesByName("OpenSim.32BitLaunch")[0];

Process[] processes = Process.GetProcessesByName("OpenSim.32BitLaunch");

foreach (Process p in processes)
{

SetForegroundWindow(p.MainWindowHandle);
Thread.Sleep(1000);
SendKeys.SendWait("restart");
Thread.Sleep(1000);
SendKeys.SendWait("{ENTER}");

}
0
Sam Hobbs15y ago
Note that in "a running process unless, of course, you launched it using the Process class in the first place", if you launch the process then it is not a running process when you redirect the I/O.

If it was important, it should be possible to inject a DLL into the process and redirect the calls to the Windows API functions but you ain't going to do that with managed code. A common way to inject code into another process is CreateRemoteThread but there are other possibilities such as Detours.

I think Vulpes's code works, so it can be used or something similar. Unless the program does not use standard input to read commands, which is possible.
0
Sam Hobbs15y ago
Are you sure it is possible to redirect the standard input or output of a running process? I doubt it.
0