Process

In C# Process.Start() calls external applications. We can start an EXE as a process. We must pass the target command along with the desired arguments.

Platform notes

The Process type is platform-neutral: we can use it to call programs on Windows, Linux or macOS. Code is resilient and cross-platform.

Exe example

We add the System.Diagnostics namespace. Our sample project is a C# .NET Core console application. But these steps will work in many configurations.

using System;
using System.Diagnostics;

class Program
{
    static void Main()
    {
        // Place exe named cwebp.exe at C directory root.
        Process.Start(@"c:\cwebp.exe",
            @"-quiet c:\programs\test.png -o c:\programs\test.webp");
        Console.WriteLine("DONE");
    }
}
DONE

Exe example 2

We can run any executable. But we may need to use properties on ProcessStartInfo. Here we run a program called cwebp.exe—it converts a certain image format.

using System;
using System.Diagnostics;

class Program
{
    static void Main()
    {
        string inputFile = @"C:\programs\test.png";
        string outputFile = @"C:\programs\test.webp";

        // Part 1: use ProcessStartInfo class.
        ProcessStartInfo startInfo = new ProcessStartInfo();
        startInfo.CreateNoWindow = false;
        startInfo.UseShellExecute = false;
        startInfo.FileName = @"c:\cwebp.exe";
        startInfo.WindowStyle = ProcessWindowStyle.Hidden;

        // Part 2: set arguments.
        startInfo.Arguments = "-q 30 " + inputFile + " -o " + outputFile;

        try
        {
            // Part 3: start with the info we specified.
            // ... Call WaitForExit.
            using (Process exeProcess = Process.Start(startInfo))
            {
                exeProcess.WaitForExit();
            }
        }
        catch
        {
            // Log error.
        }

        Console.WriteLine("DONE");
    }
}
Saving file 'C:\programs\test.webp'
File:      C:\programs\test.png
Dimension: 300 x 175
Output:    3884 bytes Y-U-V-All-PSNR 35.98 39.98 36.86   36.59 dB
block count:  intra4: 124
              intra16: 85  (-> 40.67%)
              skipped block: 33 (15.79%)
bytes used:  header:            130  (3.3%)
             mode-partition:    530  (13.6%)
 Residuals bytes  |segment 1|segment 2|segment 3|segment 4|  total
    macroblocks:  |       1%|       9%|      51%|      36%|     209
      quantizer:  |      68 |      63 |      55 |      43 |
   filter level:  |      24 |      15 |      11 |       9 |
DONE

GetProcesses

This gets an array of all the processes currently open on the system. We can loop over and test for running programs.

using System;
using System.Diagnostics;

class Program
{
    static void Main()
    {
        // Show all processes on the local computer.
        Process[] processes = Process.GetProcesses();
        // Display count.
        Console.WriteLine("Count: {0}", processes.Length);
        // Loop over processes.
        foreach (Process process in processes)
        {
            Console.WriteLine(process.Id);
        }
    }
}
Count: 70
388
5312
1564
972
2152
936
3132....

GetProcessesByName

This method returns an array of Process objects. Its functionality can be derived by combining other methods such as GetProcesses.

using System;
using System.Diagnostics;
using System.Threading;

class Program
{
    static void Main()
    {
        while (true)
        {
            // Omit the exe part.
            Process[] chromes = Process.GetProcessesByName("chrome");
            Console.WriteLine("{0} chrome processes", chromes.Length);
            Thread.Sleep(5000);
        }
    }
}
0 chrome processes
3 chrome processes
4 chrome processes
5 chrome processes
5 chrome processes
5 chrome processes

RedirectStandardOutput

With this property (found on ProcessStartInfo) we can redirect the standard output of Process. We can see program output within another program.

using System;
using System.Diagnostics;
using System.IO;

class Program
{
    static void Main()
    {
        //
        // Set up the process with the ProcessStartInfo class.
        //
        ProcessStartInfo start = new ProcessStartInfo();
        start.FileName = @"C:\7za.exe"; // Specify exe name.
        start.UseShellExecute = false;
        start.RedirectStandardOutput = true;
        //
        // Start the process.
        //
        using (Process process = Process.Start(start))
        {
            //
            // Read in all the text from the process with the StreamReader.
            //
            using (StreamReader reader = process.StandardOutput)
            {
                string result = reader.ReadToEnd();
                Console.Write(result);
            }
        }
    }
}
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Usage: 7za <command> [<switches>...] <archive_name> [<file_names>...]
       [<@listfiles...>]

Kill

It is possible to Kill or terminate a Process that we acquire a reference to. The process is not given a chance to continue running.

using System.Diagnostics;
using System.Threading;

class Program
{
    static void Main()
    {
        // Start notepad.
        Process process = Process.Start("notepad.exe");
        // Wait one second.
        Thread.Sleep(1000);
        // End notepad.
        process.Kill();
    }
}

A review

The Process type allows an external access to the operating system. With Process, we can run any EXE. We can pass command-line arguments to these programs.