Process.BeginErrorReadLine Methode

Definition

Startet asynchrone Lesevorgänge im umgeleiteten StandardError-Stream der Anwendung.Begins asynchronous read operations on the redirected StandardError stream of the application.

public:
 void BeginErrorReadLine();
public void BeginErrorReadLine ();
[System.Runtime.InteropServices.ComVisible(false)]
public void BeginErrorReadLine ();
member this.BeginErrorReadLine : unit -> unit
[<System.Runtime.InteropServices.ComVisible(false)>]
member this.BeginErrorReadLine : unit -> unit
Public Sub BeginErrorReadLine ()
Attribute

Ausnahmen

Die RedirectStandardError-Eigenschaft ist false.The RedirectStandardError property is false.

- oder --or- Für den StandardError-Stream wird bereits ein asynchroner Lesevorgang ausgeführt.An asynchronous read operation is already in progress on the StandardError stream.

- oder --or- Der StandardError-Stream wurde von einem synchronen Lesevorgang verwendet.The StandardError stream has been used by a synchronous read operation.

Beispiele

Im folgenden Beispiel wird der net view Befehl zum Auflisten der verfügbaren Netzwerkressourcen auf einem Remote Computer verwendet.The following example uses the net view command to list the available network resources on a remote computer. Der Benutzer gibt den Namen des Ziel Computers als Befehlszeilenargument an.The user supplies the target computer name as a command-line argument. Der Benutzer kann auch einen Dateinamen für die Fehlerausgabe angeben.The user can also supply a file name for error output. Im Beispiel wird die Ausgabe des NET-Befehls erfasst, auf den Abschluss des Prozesses gewartet und dann die Ausgabe Ergebnisse in die Konsole geschrieben.The example collects the output of the net command, waits for the process to finish, and then writes the output results to the console. Wenn der Benutzer die optionale Fehler Datei angibt, schreibt das Beispiel Fehler in die Datei.If the user supplies the optional error file, the example writes errors to the file.

// Define the namespaces used by this sample.
#using <System.dll>

using namespace System;
using namespace System::Text;
using namespace System::Globalization;
using namespace System::IO;
using namespace System::Diagnostics;
using namespace System::Threading;
using namespace System::ComponentModel;

ref class ProcessNetStreamRedirection
{
private:
   // Define static variables shared by class methods.
   static StreamWriter^ streamError = nullptr;
   static String^ netErrorFile = "";
   static StringBuilder^ netOutput = nullptr;
   static bool errorRedirect = false;
   static bool errorsWritten = false;

public:
   static void RedirectNetCommandStreams()
   {
      String^ netArguments;
      Process^ netProcess;
      
      // Get the input computer name.
      Console::WriteLine( "Enter the computer name for the net view command:" );
      netArguments = Console::ReadLine()->ToUpper( CultureInfo::InvariantCulture );
      if ( String::IsNullOrEmpty( netArguments ) )
      {
         // Default to the help command if there is not an input argument.
         netArguments = "/?";
      }
      
      // Check if errors should be redirected to a file.
      errorsWritten = false;
      Console::WriteLine( "Enter a fully qualified path to an error log file" );
      Console::WriteLine( "  or just press Enter to write errors to console:" );
      netErrorFile = Console::ReadLine()->ToUpper( CultureInfo::InvariantCulture );
      if (  !String::IsNullOrEmpty( netErrorFile ) )
      {
         errorRedirect = true;
      }
      
      // Note that at this point, netArguments and netErrorFile
      // are set with user input.  If the user did not specify
      // an error file, then errorRedirect is set to false.

      // Initialize the process and its StartInfo properties.
      netProcess = gcnew Process;
      netProcess->StartInfo->FileName = "Net.exe";
      
      // Build the net command argument list.
      netProcess->StartInfo->Arguments = String::Format( "view {0}", netArguments );
      
      // Set UseShellExecute to false for redirection.
      netProcess->StartInfo->UseShellExecute = false;
      
      // Redirect the standard output of the net command.  
      // This stream is read asynchronously using an event handler.
      netProcess->StartInfo->RedirectStandardOutput = true;
      netProcess->OutputDataReceived += gcnew DataReceivedEventHandler( NetOutputDataHandler );
      netOutput = gcnew StringBuilder;
      if ( errorRedirect )
      {
         
         // Redirect the error output of the net command. 
         netProcess->StartInfo->RedirectStandardError = true;
         netProcess->ErrorDataReceived += gcnew DataReceivedEventHandler( NetErrorDataHandler );
      }
      else
      {
         
         // Do not redirect the error output.
         netProcess->StartInfo->RedirectStandardError = false;
      }

      Console::WriteLine( "\nStarting process: net {0}",
         netProcess->StartInfo->Arguments );
      if ( errorRedirect )
      {
         Console::WriteLine( "Errors will be written to the file {0}", netErrorFile );
      }
      
      // Start the process.
      netProcess->Start();
      
      // Start the asynchronous read of the standard output stream.
      netProcess->BeginOutputReadLine();

      if ( errorRedirect )
      {
         // Start the asynchronous read of the standard
         // error stream.
         netProcess->BeginErrorReadLine();
      }
      
      // Let the net command run, collecting the output.
      netProcess->WaitForExit();

      if ( streamError != nullptr )
      {
         // Close the error file.
         streamError->Close();
      }
      else
      {
         // Set errorsWritten to false if the stream is not
         // open.   Either there are no errors, or the error
         // file could not be opened.
         errorsWritten = false;
      }

      if ( netOutput->Length > 0 )
      {
         // If the process wrote more than just
         // white space, write the output to the console.
         Console::WriteLine( "\nPublic network shares from net view:\n{0}\n",
            netOutput->ToString() );
      }

      if ( errorsWritten )
      {
         // Signal that the error file had something 
         // written to it.
         array<String^>^errorOutput = File::ReadAllLines( netErrorFile );
         if ( errorOutput->Length > 0 )
         {
            Console::WriteLine( "\nThe following error output was appended to {0}.",
               netErrorFile );
            System::Collections::IEnumerator^ myEnum = errorOutput->GetEnumerator();
            while ( myEnum->MoveNext() )
            {
               String^ errLine = safe_cast<String^>(myEnum->Current);
               Console::WriteLine( "  {0}", errLine );
            }
         }
         Console::WriteLine();
      }

      netProcess->Close();

   }

private:
   static void NetOutputDataHandler( Object^ /*sendingProcess*/,
      DataReceivedEventArgs^ outLine )
   {
      // Collect the net view command output.
      if (  !String::IsNullOrEmpty( outLine->Data ) )
      {
         // Add the text to the collected output.
         netOutput->AppendFormat(  "\n  {0}", outLine->Data );
      }
   }

   static void NetErrorDataHandler( Object^ /*sendingProcess*/,
      DataReceivedEventArgs^ errLine )
   {
      // Write the error text to the file if there is something to 
      // write and an error file has been specified.

      if (  !String::IsNullOrEmpty( errLine->Data ) )
      {
         if (  !errorsWritten )
         {
            if ( streamError == nullptr )
            {
               // Open the file.
               try
               {
                  streamError = gcnew StreamWriter( netErrorFile,true );
               }
               catch ( Exception^ e ) 
               {
                  Console::WriteLine(  "Could not open error file!" );
                  Console::WriteLine( e->Message->ToString() );
               }
            }

            if ( streamError != nullptr )
            {
               // Write a header to the file if this is the first
               // call to the error output handler.
               streamError->WriteLine();
               streamError->WriteLine( DateTime::Now.ToString() );
               streamError->WriteLine(  "Net View error output:" );
            }
            errorsWritten = true;
         }

         if ( streamError != nullptr )
         {
            // Write redirected errors to the file.
            streamError->WriteLine( errLine->Data );
            streamError->Flush();
         }
      }
   }
};
// Define the namespaces used by this sample.
using System;
using System.Text;
using System.Globalization;
using System.IO;
using System.Diagnostics;
using System.Threading;
using System.ComponentModel;

namespace ProcessAsyncStreamSamples
{

    class ProcessNetStreamRedirection
    {
        // Define static variables shared by class methods.
        private static StreamWriter streamError =null;
        private static String netErrorFile = "";
        private static StringBuilder netOutput = null;
        private static bool errorRedirect = false;
        private static bool errorsWritten = false;

        public static void RedirectNetCommandStreams()
        {
            String netArguments;
            Process netProcess;

            // Get the input computer name.
            Console.WriteLine("Enter the computer name for the net view command:");
            netArguments = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture);
            if (String.IsNullOrEmpty(netArguments))
            {
                // Default to the help command if there is not an input argument.
                netArguments = "/?";
            }

            // Check if errors should be redirected to a file.
            errorsWritten = false;
            Console.WriteLine("Enter a fully qualified path to an error log file");
            Console.WriteLine("  or just press Enter to write errors to console:");
            netErrorFile = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture);
            if (!String.IsNullOrEmpty(netErrorFile))
            {
                errorRedirect = true;
            }

            // Note that at this point, netArguments and netErrorFile
            // are set with user input.  If the user did not specify
            // an error file, then errorRedirect is set to false.

            // Initialize the process and its StartInfo properties.
            netProcess = new Process();
            netProcess.StartInfo.FileName = "Net.exe";

            // Build the net command argument list.
            netProcess.StartInfo.Arguments = String.Format("view {0}",
                netArguments);

            // Set UseShellExecute to false for redirection.
            netProcess.StartInfo.UseShellExecute = false;

            // Redirect the standard output of the net command.
            // This stream is read asynchronously using an event handler.
            netProcess.StartInfo.RedirectStandardOutput = true;
            netProcess.OutputDataReceived += new DataReceivedEventHandler(NetOutputDataHandler);
            netOutput = new StringBuilder();

            if (errorRedirect)
            {
                // Redirect the error output of the net command.
                netProcess.StartInfo.RedirectStandardError = true;
                netProcess.ErrorDataReceived += new DataReceivedEventHandler(NetErrorDataHandler);
            }
            else
            {
                // Do not redirect the error output.
                netProcess.StartInfo.RedirectStandardError = false;
            }

            Console.WriteLine("\nStarting process: net {0}",
                netProcess.StartInfo.Arguments);
            if (errorRedirect)
            {
                Console.WriteLine("Errors will be written to the file {0}",
                    netErrorFile);
            }

            // Start the process.
            netProcess.Start();

            // Start the asynchronous read of the standard output stream.
            netProcess.BeginOutputReadLine();

            if (errorRedirect)
            {
                // Start the asynchronous read of the standard
                // error stream.
                netProcess.BeginErrorReadLine();
            }

            // Let the net command run, collecting the output.
            netProcess.WaitForExit();

            if (streamError != null)
            {
                // Close the error file.
                streamError.Close();
            }
            else
            {
                // Set errorsWritten to false if the stream is not
                // open.   Either there are no errors, or the error
                // file could not be opened.
                errorsWritten = false;
            }

            if (netOutput.Length > 0)
            {
                // If the process wrote more than just
                // white space, write the output to the console.
                Console.WriteLine("\nPublic network shares from net view:\n{0}\n",
                    netOutput);
            }

            if (errorsWritten)
            {
                // Signal that the error file had something
                // written to it.
                String [] errorOutput = File.ReadAllLines(netErrorFile);
                if (errorOutput.Length > 0)
                {
                    Console.WriteLine("\nThe following error output was appended to {0}.",
                        netErrorFile);
                    foreach (String errLine in errorOutput)
                    {
                        Console.WriteLine("  {0}", errLine);
                    }
                }
                Console.WriteLine();
            }

            netProcess.Close();
        }

        private static void NetOutputDataHandler(object sendingProcess,
            DataReceivedEventArgs outLine)
        {
            // Collect the net view command output.
            if (!String.IsNullOrEmpty(outLine.Data))
            {
                // Add the text to the collected output.
                netOutput.Append(Environment.NewLine + "  " + outLine.Data);
            }
        }

        private static void NetErrorDataHandler(object sendingProcess,
            DataReceivedEventArgs errLine)
        {
            // Write the error text to the file if there is something
            // to write and an error file has been specified.

            if (!String.IsNullOrEmpty(errLine.Data))
            {
                if (!errorsWritten)
                {
                    if (streamError == null)
                    {
                        // Open the file.
                        try
                        {
                            streamError = new StreamWriter(netErrorFile, true);
                        }
                        catch (Exception e)
                        {
                            Console.WriteLine("Could not open error file!");
                            Console.WriteLine(e.Message.ToString());
                        }
                    }

                    if (streamError != null)
                    {
                        // Write a header to the file if this is the first
                        // call to the error output handler.
                        streamError.WriteLine();
                        streamError.WriteLine(DateTime.Now.ToString());
                        streamError.WriteLine("Net View error output:");
                    }
                    errorsWritten = true;
                }

                if (streamError != null)
                {
                    // Write redirected errors to the file.
                    streamError.WriteLine(errLine.Data);
                    streamError.Flush();
                }
            }
        }
    }
}
' Define the namespaces used by this sample.
Imports System.Text
Imports System.Globalization
Imports System.IO
Imports System.Diagnostics
Imports System.Threading
Imports System.ComponentModel

Namespace ProcessAsyncStreamSamples
   
   Class ProcessAsyncErrorRedirection
      ' Define static variables shared by class methods.
      Private Shared streamError As StreamWriter = Nothing
      Private Shared netErrorFile As String = ""
      Private Shared netOutput As StringBuilder = Nothing
      Private Shared errorRedirect As Boolean = False
      Private Shared errorsWritten As Boolean = False
      
      Public Shared Sub RedirectNetCommandStreams()
         Dim netArguments As String
         Dim netProcess As Process
         
         ' Get the input computer name.
         Console.WriteLine("Enter the computer name for the net view command:")
         netArguments = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture)
         If String.IsNullOrEmpty(netArguments) Then
            ' Default to the help command if there is 
            ' not an input argument.
            netArguments = "/?"
         End If
         
         ' Check if errors should be redirected to a file.
         errorsWritten = False
         Console.WriteLine("Enter a fully qualified path to an error log file")
         Console.WriteLine("  or just press Enter to write errors to console:")
         netErrorFile = Console.ReadLine().ToUpper(CultureInfo.InvariantCulture)
         If Not String.IsNullOrEmpty(netErrorFile) Then
            errorRedirect = True
         End If
         
         ' Note that at this point, netArguments and netErrorFile
         ' are set with user input.  If the user did not specify
         ' an error file, then errorRedirect is set to false.

         ' Initialize the process and its StartInfo properties.
         netProcess = New Process()
         netProcess.StartInfo.FileName = "Net.exe"
         
         ' Build the net command argument list.
         netProcess.StartInfo.Arguments = String.Format("view {0}", _
                                                        netArguments)
         
         ' Set UseShellExecute to false for redirection.
         netProcess.StartInfo.UseShellExecute = False
         
         ' Redirect the standard output of the net command.  
         ' Read the stream asynchronously using an event handler.
         netProcess.StartInfo.RedirectStandardOutput = True
         AddHandler netProcess.OutputDataReceived, _
                            AddressOf NetOutputDataHandler
         netOutput = new StringBuilder()
         
         If errorRedirect Then
            ' Redirect the error output of the net command. 
            netProcess.StartInfo.RedirectStandardError = True
            AddHandler netProcess.ErrorDataReceived, _
                            AddressOf NetErrorDataHandler
         Else
            ' Do not redirect the error output.
            netProcess.StartInfo.RedirectStandardError = False
         End If
         
         Console.WriteLine(ControlChars.Lf + "Starting process: NET {0}", _
                           netProcess.StartInfo.Arguments)
         If errorRedirect Then
            Console.WriteLine("Errors will be written to the file {0}", _
                           netErrorFile)
         End If
         
         ' Start the process.
         netProcess.Start()
         
         ' Start the asynchronous read of the standard output stream.
         netProcess.BeginOutputReadLine()
         
         If errorRedirect Then
            ' Start the asynchronous read of the standard
            ' error stream.
            netProcess.BeginErrorReadLine()
         End If
         
         ' Let the net command run, collecting the output.
         netProcess.WaitForExit()
      
         If Not streamError Is Nothing Then
             ' Close the error file.
             streamError.Close()
         Else 
             ' Set errorsWritten to false if the stream is not
             ' open.   Either there are no errors, or the error
             ' file could not be opened.
             errorsWritten = False
         End If
   
         If netOutput.Length > 0 Then
            ' If the process wrote more than just
            ' white space, write the output to the console.
            Console.WriteLine()
            Console.WriteLine("Public network shares from net view:")
            Console.WriteLine()
            Console.WriteLine(netOutput)
            Console.WriteLine()
         End If
         
         If errorsWritten Then
            ' Signal that the error file had something 
            ' written to it.
            Dim errorOutput As String()
            errorOutput = File.ReadAllLines(netErrorFile)
            If errorOutput.Length > 0 Then

                Console.WriteLine(ControlChars.Lf + _
                    "The following error output was appended to {0}.", _
                    netErrorFile)
                Dim errLine as String
                For Each errLine in errorOutput
                    Console.WriteLine("  {0}", errLine)
                Next
          
                Console.WriteLine()
            End If
         End If
         
         netProcess.Close()
      End Sub 
      
      
      Private Shared Sub NetOutputDataHandler(sendingProcess As Object, _
          outLine As DataReceivedEventArgs)

         ' Collect the net view command output.
         If Not String.IsNullOrEmpty(outLine.Data) Then
            ' Add the text to the collected output.
            netOutput.Append(Environment.NewLine + "  " + outLine.Data)
         End If
      End Sub 
       
      
      Private Shared Sub NetErrorDataHandler(sendingProcess As Object, _
          errLine As DataReceivedEventArgs)

         ' Write the error text to the file if there is something to
         ' write and an error file has been specified.

         If Not String.IsNullOrEmpty(errLine.Data) Then

            If Not errorsWritten Then
                If streamError Is Nothing Then
                    ' Open the file.
                    Try 
                        streamError = New StreamWriter(netErrorFile, true)
                    Catch e As Exception
                        Console.WriteLine("Could not open error file!")
                        Console.WriteLine(e.Message.ToString())
                    End Try
                End If

                If Not streamError Is Nothing Then

                    ' Write a header to the file if this is the first
                    ' call to the error output handler.
                    streamError.WriteLine()
                    streamError.WriteLine(DateTime.Now.ToString())
                    streamError.WriteLine("Net View error output:")

                End If

                errorsWritten = True
            End If
                     
            If Not streamError Is Nothing Then
                  
                ' Write redirected errors to the file.
                streamError.WriteLine(errLine.Data)
                streamError.Flush()
             End If
          End If
      End Sub 
   End Class  
End Namespace 

Hinweise

Der StandardError Stream kann synchron oder asynchron gelesen werden.The StandardError stream can be read synchronously or asynchronously. Methoden wie Read , ReadLine und ReadToEnd führen synchrone Lesevorgänge im Fehlerausgabestream des Prozesses aus.Methods such as Read, ReadLine, and ReadToEnd perform synchronous read operations on the error output stream of the process. Diese synchronen Lesevorgänge werden erst abgeschlossen, wenn die zugeordnete Process in Ihren StandardError Stream schreibt, oder der Stream wird geschlossen.These synchronous read operations do not complete until the associated Process writes to its StandardError stream, or closes the stream.

Im Gegensatz dazu BeginErrorReadLine startet asynchrone Lesevorgänge im StandardError Stream.In contrast, BeginErrorReadLine starts asynchronous read operations on the StandardError stream. Diese Methode aktiviert den festgelegten Ereignishandler für die Datenstrom Ausgabe und kehrt sofort an den Aufrufer zurück, der andere Aufgaben ausführen kann, während die Datenstrom Ausgabe an den Ereignishandler weitergeleitet wird.This method enables the designated event handler for the stream output and immediately returns to the caller, which can perform other work while the stream output is directed to the event handler.

Führen Sie die folgenden Schritte aus, um asynchrone Lesevorgänge StandardError für eine auszuführen Process :Follow these steps to perform asynchronous read operations on StandardError for a Process :

  1. Legen Sie UseShellExecute auf false fest.Set UseShellExecute to false.

  2. Legen Sie RedirectStandardError auf true fest.Set RedirectStandardError to true.

  3. Fügen Sie dem-Ereignis den Ereignishandler hinzu ErrorDataReceived .Add your event handler to the ErrorDataReceived event. Der Ereignishandler muss der Signatur des Delegaten entsprechen System.Diagnostics.DataReceivedEventHandler .The event handler must match the System.Diagnostics.DataReceivedEventHandler delegate signature.

  4. Starten Sie die Process.Start the Process.

  5. Ruft BeginErrorReadLine für den-Befehl auf Process .Call BeginErrorReadLine for the Process. Mit diesem-Befehl werden asynchrone Lesevorgänge für gestartet StandardError .This call starts asynchronous read operations on StandardError.

Wenn asynchrone Lesevorgänge gestartet werden, wird der Ereignishandler jedes Mal aufgerufen, wenn die zugeordnete Process eine Textzeile in den StandardError Stream schreibt.When asynchronous read operations start, the event handler is called each time the associated Process writes a line of text to its StandardError stream.

Sie können einen asynchronen Lesevorgang abbrechen, indem Sie aufrufen CancelErrorRead .You can cancel an asynchronous read operation by calling CancelErrorRead. Der Lesevorgang kann vom Aufrufer oder vom Ereignishandler abgebrochen werden.The read operation can be canceled by the caller or by the event handler. Nach dem abbrechen können Sie erneut einen Rückruf ausführen, BeginErrorReadLine um asynchrone Lesevorgänge fortzusetzen.After canceling, you can call BeginErrorReadLine again to resume asynchronous read operations.

Hinweis

Asynchrone und synchrone Lesevorgänge können nicht in einem umgeleiteten Stream gemischt werden.You cannot mix asynchronous and synchronous read operations on a redirected stream. Sobald der umgeleitete Stream eines Process im asynchronen oder im synchronen Modus geöffnet ist, müssen sich alle weiteren Lesevorgänge in diesem Stream im gleichen Modus befinden.Once the redirected stream of a Process is opened in either asynchronous or synchronous mode, all further read operations on that stream must be in the same mode. Folgen Sie z BeginErrorReadLine . b. nicht mit einem aufrufen ReadLine von für den StandardError Stream oder umgekehrt.For example, do not follow BeginErrorReadLine with a call to ReadLine on the StandardError stream, or vice versa. Sie können jedoch zwei verschiedene Streams in verschiedenen Modi lesen.However, you can read two different streams in different modes. Sie können z. b. aufzurufen BeginErrorReadLine und dann ReadLine für den Stream aufzurufen StandardOutput .For example, you can call BeginErrorReadLine and then call ReadLine for the StandardOutput stream.

Gilt für:

Siehe auch