"Query User" called via CMD.exe from C# results 0 Output-CodePudding

i am trying to call and collect the data returned by the CMD command query user.

Calling this via cmd from the Windows-startbar gives me a normal result.

Calling this via this c# function give 0 output.

     public void callQueryUser()
        {
            ProcessStartInfo psi = new ProcessStartInfo("cmd.exe");
            Process p = Process.Start(psi);

            string cmd = string.Format(@"/c query user");
             
            psi.Arguments = cmd;
                                
            psi.RedirectStandardOutput = true;
            psi.UseShellExecute = false;
            psi.CreateNoWindow = true;
            psi.WaitForExit();
           
            string result = p.StandardOutput.ReadToEnd();
            MessageBox.Show(result);
        }

I checked and the Window says command cant befound... I also check if they are both the same cmd.exe and thats also true. It seems like calling the cmd.exe via C# makes somewhat of a differences. Anyone any idea what i could check next ?

CodePudding user response：

It's not necessary to use cmd to retrieve the information you want using Process. However, if your OS is 64-bit, your program is running as 32-bit, and you're trying to access %windir%\System32\query.exe, you need to use %windir%\Sysnative\query.exe instead.

Try the following:

Option 1:

public void callQueryUser()
{
    string queryPath = string.Empty;

    //use 'Sysnative' to access 64-bit files (in System32) if program is running as 32-bit process
    //use 'SysWow64' to access 32-bit files on 64-bit OS
    if (Environment.Is64BitOperatingSystem && !Environment.Is64BitProcess)
        queryPath = System.IO.Path.Combine(Environment.GetEnvironmentVariable("windir"), "Sysnative", "query.exe");
    else
        queryPath = System.IO.Path.Combine(Environment.GetEnvironmentVariable("windir"), "System32", "query.exe");

    Debug.WriteLine("queryPath: "   queryPath);

    // create new instance
    ProcessStartInfo startInfo = new ProcessStartInfo(queryPath);
    startInfo.Arguments = "user"; //arguments
    startInfo.CreateNoWindow = true; //don't create a window
    startInfo.RedirectStandardError = true; //redirect standard error
    startInfo.RedirectStandardOutput = true; //redirect standard output
    startInfo.UseShellExecute = false; //if true, uses 'ShellExecute'; if false, uses 'CreateProcess'
    startInfo.WindowStyle = ProcessWindowStyle.Hidden;

    //create new instance
    using (Process p = new Process { StartInfo = startInfo, EnableRaisingEvents = true })
    {
        //subscribe to event and add event handler code
        p.ErrorDataReceived  = (sender, e) =>
        {
            if (!String.IsNullOrEmpty(e.Data))
            {
                //ToDo: add desired code 
                Debug.WriteLine("Error: "   e.Data);
            }
        };

        //subscribe to event and add event handler code
        p.OutputDataReceived  = (sender, e) =>
        {
            if (!String.IsNullOrEmpty(e.Data))
            {
                //ToDo: add desired code
                Debug.WriteLine("Output: "   e.Data);

                string result = e.Data;
                MessageBox.Show(result);
            }
        };

        p.Start(); //start

        p.BeginErrorReadLine(); //begin async reading for standard error
        p.BeginOutputReadLine(); //begin async reading for standard output

        //waits until the process is finished before continuing
        p.WaitForExit();
    } 
}

Option 2:

public void callQueryUser()
{
    string queryPath = string.Empty;

    //environment variable windir has the same value as SystemRoot
    //use 'Sysnative' to access 64-bit files (in System32) if program is running as 32-bit process
    //use 'SysWow64' to access 32-bit files on 64-bit OS
    if (Environment.Is64BitOperatingSystem && !Environment.Is64BitProcess)
        queryPath = System.IO.Path.Combine(Environment.GetEnvironmentVariable("windir"), "Sysnative", "query.exe");
    else
        queryPath = System.IO.Path.Combine(Environment.GetEnvironmentVariable("windir"), "System32", "query.exe");

    Debug.WriteLine("queryPath: "   queryPath);

    // create new instance
    ProcessStartInfo startInfo = new ProcessStartInfo(queryPath);
    startInfo.Arguments = "user"; //arguments
    startInfo.CreateNoWindow = true; //don't create a window
    startInfo.RedirectStandardError = true; //redirect standard error
    startInfo.RedirectStandardOutput = true; //redirect standard output
    startInfo.UseShellExecute = false; //if true, uses 'ShellExecute'; if false, uses 'CreateProcess'
    startInfo.WindowStyle = ProcessWindowStyle.Hidden;

    //create new instance
    using (Process p = new Process { StartInfo = startInfo, EnableRaisingEvents = true })
    {
        p.Start(); //start

        //waits until the process is finished before continuing
        p.WaitForExit();

        string result = p.StandardOutput.ReadToEnd();
        MessageBox.Show(result);
    }
}

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