How to get the output of a System.Diagnostics.Process?

Question

I run ffmpeg like this:

System.Diagnostics.Process p = new System.Diagnostics.Process(); p.StartInfo = new System.Diagnostics.ProcessStartInfo(ffmpegPath, myParams); p.Start(); p.WaitForExit(); 

... but the problem is that the console with ffmpeg pops up and disappears right away, so I can't get any feedback. I don't even know if the process ran correctly.

So how can I either:

• Tell the console to stay opened

• Retrieve in the C# what the console displayed

Answer 1

What you need to do is capture the Standard Output stream:

p.StartInfo.RedirectStandardOutput = true; p.StartInfo.UseShellExecute = false; // instead of p.WaitForExit(), do string q = ""; while ( ! p.HasExited ) {     q += p.StandardOutput.ReadToEnd(); } 

You may also need to do something similar with StandardError. You can then do what you wish with q.

It is a bit finicky, as I discovered in one of my questions

As Jon Skeet has pointed out, it is not smart performance-wise to use string concatenation like this; you should instead use a StringBuilder:

p.StartInfo.RedirectStandardOutput = true; p.StartInfo.UseShellExecute = false; // instead of p.WaitForExit(), do StringBuilder q = new StringBuilder(); while ( ! p.HasExited ) {     q.Append(p.StandardOutput.ReadToEnd()); } string r = q.ToString();