Executing external applications

Some interesting information about setting up an external application (command line) and executing it without a visible window. Allows for capturing the stdout, stdin and stderr streams too. This example is for launching the command line svn client with info argument about a specific file in the svn repository, and capturing the result of our query.

   1:  Process svnProcess = new Process();

   2:  svnProcess.StartInfo.FileName = "svn.exe";

   3:  svnProcess.StartInfo.Arguments = " info " + svnUri;

   4:  svnProcess.StartInfo.UseShellExecute = false;

   5:  svnProcess.StartInfo.RedirectStandardOutput = true;

   6:  svnProcess.StartInfo.RedirectStandardError = true;

   7:  svnProcess.StartInfo.RedirectStandardInput = true;

   8:  svnProcess.StartInfo.WindowStyle = ProcessWindowStyle.Hidden;

   9:  svnProcess.StartInfo.CreateNoWindow = true;

  10:   

  11:  try

  12:  {

  13:      bool started = svnProcess.Start();

  14:      if (!started)

  15:      {

  16:          Log.WriteLog("Unable to start svn.exe process, aborting.", "svnInfoError.log", true, true);

  17:          MessageBox.Show("Unable to start svn.exe process.", "Error launching svn.exe", MessageBoxButtons.OK, MessageBoxIcon.Error);

  18:          return -1;

  19:      }

  20:  }

  21:  catch (Exception ex)

  22:  {

  23:      Log.WriteLog("Unable to start svn.exe process, aborting.", "svnInfoError.log", true, true);

  24:      MessageBox.Show("Unable to start svn.exe process.", "Error launching svn.exe", MessageBoxButtons.OK, MessageBoxIcon.Error);

  25:      return -1;

  26:  }

  27:   

  28:  StreamReader sOut = svnProcess.StandardOutput;

  29:  string output;

  30:   

  31:  while (svnProcess.HasExited == false)

  32:  {

  33:      output = sOut.ReadLine();

  34:      if (output != null)

  35:      {

  36:          if (output.StartsWith("Last Changed Rev: "))

  37:          {

  38:              string revNumberString = output.Substring("Last Changed Rev: ".Length);

  39:              int revNumber;

  40:              if (int.TryParse(revNumberString, out revNumber))

  41:              {

  42:                  sOut.Close();

  43:                  return revNumber;

  44:              }

  45:              else

  46:              {

  47:                  throw new Exception("Could not parse the svn revision number!!!");

  48:              }

  49:          }

  50:      }

  51:  }

  52:   

  53:  do

  54:  {

  55:      output = sOut.ReadLine();

  56:      if (output != null)

  57:      {

  58:          if (output.StartsWith("Last Changed Rev: "))

  59:          {

  60:              string revNumberString = output.Substring("Last Changed Rev: ".Length);

  61:              int revNumber;

  62:              if (int.TryParse(revNumberString, out revNumber))

  63:              {

  64:                  sOut.Close();

  65:                  return revNumber;

  66:              }

  67:              else

  68:              {

  69:                  throw new Exception("Could not parse the svn revision number!!!");

  70:              }

  71:          }

  72:      }

  73:  } while (output != null);

  74:   

  75:   

  76:  string error = svnProcess.StandardError.ReadToEnd();

  77:  if (string.IsNullOrEmpty(error) == false)

  78:  {

  79:      Log.WriteLog(error, "svnInfoError.log", true, true);

  80:   

  81:  }

  82:  return -1; // Error executing the svn client application!!!