Process.BeginErrorReadLine Metodo
Definizione
Importante
Alcune informazioni sono relative alla release non definitiva del prodotto, che potrebbe subire modifiche significative prima della release definitiva. Microsoft non riconosce alcuna garanzia, espressa o implicita, in merito alle informazioni qui fornite.
Inizia le operazioni di lettura asincrona sul flusso StandardError reindirizzato dell'applicazione.
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 -> unitPublic Sub BeginErrorReadLine ()- Attributi
Eccezioni
La proprietà RedirectStandardError è false.
-oppure-
È già in corso un'operazione di lettura asincrona sul flusso StandardError.
-oppure-
Il flusso StandardError è stato usato da un'operazione di lettura sincrona.
Esempio
Nell'esempio seguente viene usato il net view comando per elencare le risorse di rete disponibili in un computer remoto. L'utente specifica il nome del computer di destinazione come argomento della riga di comando. L'utente può anche fornire un nome file per l'output degli errori. L'esempio raccoglie l'output del comando net, attende il completamento del processo e quindi scrive i risultati di output nella console. Se l'utente fornisce il file di errore facoltativo, nell'esempio vengono scritti errori nel 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
Commenti
Il StandardError flusso può essere letto in modo sincrono o asincrono. Metodi come Read, ReadLineed ReadToEnd eseguono operazioni di lettura sincrone nel flusso di output degli errori del processo. Queste operazioni di lettura sincrone non vengono completate fino a quando le scritture associate Process nel flusso StandardError non vengono completate o chiude il flusso.
Al contrario, BeginErrorReadLine avvia operazioni di lettura asincrone nel StandardError flusso. Questo metodo abilita il gestore eventi designato per l'output del flusso e torna immediatamente al chiamante, che può eseguire altre operazioni mentre l'output del flusso viene indirizzato al gestore eventi.
Seguire questa procedura per eseguire operazioni di lettura asincrone su StandardError per un Process oggetto :
Impostare UseShellExecute su
false.Impostare RedirectStandardError su
true.Aggiungere il gestore eventi all'evento ErrorDataReceived . Il gestore eventi deve corrispondere alla firma del System.Diagnostics.DataReceivedEventHandler delegato.
Avviare il Process.
Chiamare BeginErrorReadLine per .Process Questa chiamata avvia operazioni di lettura asincrone su StandardError.
All'avvio delle operazioni di lettura asincrone, il gestore eventi viene chiamato ogni volta che l'oggetto associato Process scrive una riga di testo nel flusso StandardError .
È possibile annullare un'operazione di lettura asincrona chiamando CancelErrorRead. L'operazione di lettura può essere annullata dal chiamante o dal gestore eventi. Dopo l'annullamento, è possibile chiamare BeginErrorReadLine di nuovo per riprendere le operazioni di lettura asincrone.
Nota
Non è possibile combinare operazioni di lettura asincrone e sincrone in un flusso reindirizzato. Dopo l'apertura del flusso reindirizzato di un Process oggetto in modalità asincrona o sincrona, tutte le altre operazioni di lettura su tale flusso devono trovarsi nella stessa modalità. Ad esempio, non seguire BeginErrorReadLine con una chiamata a ReadLine sul StandardError flusso o viceversa. Tuttavia, è possibile leggere due flussi diversi in modalità diverse. Ad esempio, è possibile chiamare e quindi chiamare BeginErrorReadLineReadLine per il StandardOutput flusso.
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