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Editorial Team
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Asked: 2026-06-08T12:40:24+00:00

I’ve a problem understanding the in’s and out’s of the ProcessStartInfo class in .NET.

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I’ve a problem understanding the in’s and out’s of the ProcessStartInfo class in .NET.
I use this class for executing .exe programs like FFmpeg with no issues whatsoever.

But when I use ProcessStartInfo to start a .cmd program like a simple foo.cmd containing only @echo Hello world it doesn’t output anything.

    ProcessStartInfo oInfo = new ProcessStartInfo(@"C:\Program Files (x86)\itms\foo.cmd")
    {
        UseShellExecute = false,
        RedirectStandardError = true,
        RedirectStandardOutput = true,
        CreateNoWindow = true
    };

    using (Process p = new Process())
    {
        p.StartInfo = oInfo;
        p.OutputDataReceived += new DataReceivedEventHandler(transporter_OutputDataReceived);

        p.Start();

        p.BeginOutputReadLine();

        p.WaitForExit();
    }

private void transporter_OutputDataReceived(object sender, DataReceivedEventArgs e)
{
    Response.Write(e.Data + " - line<br/>");
}

I’ve seen a bunch of examples, where people use cmd.exe to start the .cmd program and I’ve tried this, but with no success. The program just keeps loading indefinitely.

    ProcessStartInfo oInfo = new ProcessStartInfo("cmd", "/c start foo.cmd")
    {
        UseShellExecute = false,
        RedirectStandardError = true,
        RedirectStandardOutput = true,
        CreateNoWindow = true,
        WorkingDirectory = @"C:\Program Files (x86)\itms"
    };

The foo.cmd program works and outputs successfully when using a command line tool in Windows and on Mac.

Could someone please demystify this for me.

Thanks

EDIT

The code behaves correctly when executed locally. The problem arises when I execute the code on our website. Either the program isn’t allowed to execute or the output is somehow disabled.

Only cmd.exe is returning output ´”cmd”, “/c dir”´ is e.g. returning information about the current folder content.

Could this actually be a permission issue?

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1 Answer

  1. Editorial Team

    I found the answer myself and will post a solution for anyone interested.

    The source of the issue is fairly hard to debug, because the problem originated in how IIS handles users and processes.

    As I thought, there was nothing wrong with the code itself.

    Answer

    In IIS, a website is running in a AppPool. An AppPool is assigned an user identity. The default identity is a virtual built-in account named ApplicationPoolIdentity. This user does not have the privilege to call any (as far as I know) external batch/command scripts.

    Providing a username, password and domain for a administrative user when starting a new process, didn’t solve anything for me – It might be that I’m just misunderstanding the whole concept.

    Using <identity impersonate="true" userName="domain\user" password="pass" /> in the webconfig didn’t solve anything either. This is apparently because the assigned AppPool user is still the author of all processes.

    What really bugged me out, was that I could execute .exe files, but not .cmd or .bat files.

    The solution for me, was to create a new user with privileges to execute batch scripts and select that user as the AppPool user in IIS.

    Edit: As I have mentioned in the comments, the user I’m working with is created on an Active Directory server as this particular file server is on a network share. The user is part of the local server group IIS_IUSRS on my webserver and has read/write/execute privileges in the folder where the executable programs are stored.

    Edit2: The solution works for local user accounts as well as long as the user is part of the local server group IIS_IUSRS and has read/write/execute privileges in the folder where the executable programs are stored.

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