CODEWITHSUNDEEP
c#
RPS
RPS

Reputation: 113

C# - Read the standard output byte by byte from an external command line application

I am looking for a way to read the standard output byte by byte from an external command line application.

The current code works, but only when a newline is added. Is there a way to read the current line input byte by byte so I can update the user with progress.

Ex)

Proccesing file

0%   10   20   30   40   50   60   70   80   90   100%

|----|----|----|----|----|----|----|----|----|----|

xxxxxx

A x is added every few minutes in the console application but not in my c# Win form as it only updates when it has completed with the current line (the end)

Sample code:

Process VSCmd = new Process();
VSCmd.StartInfo = new ProcessStartInfo("c:\\testapp.exe");
VSCmd.StartInfo.Arguments = "--action run"
VSCmd.StartInfo.RedirectStandardOutput = true;
VSCmd.StartInfo.RedirectStandardError = true;
VSCmd.StartInfo.UseShellExecute = false;
VSCmd.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;
VSCmd.StartInfo.CreateNoWindow = true;

VSCmd.Start();

StreamReader sr = VSCmd.StandardOutput;

while ((s = sr.ReadLine()) != null)
{
   strLog += s + "\r\n";
   invoker.Invoke(updateCallback, new object[] { strLog });
}


VSCmd.WaitForExit();

Upvotes: 3

Views: 1377

Answers (2)

Chris Taylor
Chris Taylor

Reputation: 53699

The following will build up strLog character by character, I assumed you wanted to invoke updateCallback for each line, of course if this is not the case then you can remove the check for new line.

  int currChar;
  int prevChar = 0;
  string strLog = string.Empty;
  while ((currChar = sr.Read()) != -1)
  {
    strLog += (char)currChar; // You should use a StringBuilder here!
    if (prevChar == 13 && currChar == 10) // Remove if you need to invoke for each char
    {
      invoker.Invoke(updateCallback, new object[] { strLog });
    }

    prevChar = currChar;
  }

Upvotes: 0

Julien Lebosquain
Julien Lebosquain

Reputation: 41223

Try to use StreamReader.Read() to read the next available character from the stream without waiting for the full line. This function returns an int that is -1 is the end of the stream has been reached, or can be cast to a char otherwise.

Upvotes: 2

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