Process.CancelErrorRead 方法
定义
重要
一些信息与预发行产品相关，相应产品在发行之前可能会进行重大修改。 对于此处提供的信息，Microsoft 不作任何明示或暗示的担保。
取消在应用程序的重定向 StandardError 流上执行的异步读取操作。
public:
void CancelErrorRead();public void CancelErrorRead ();[System.Runtime.InteropServices.ComVisible(false)]
public void CancelErrorRead ();member this.CancelErrorRead : unit -> unit[<System.Runtime.InteropServices.ComVisible(false)>]
member this.CancelErrorRead : unit -> unitPublic Sub CancelErrorRead ()- 属性
例外
未针对异步读取操作启用 StandardError 流。
示例
以下示例使用用户提供的参数启动 nmake 命令。 错误和输出流以异步方式读取;收集的文本行会显示到控制台以及写入日志文件。 如果命令输出超过指定的行数，将取消异步读取操作。
ref class ProcessNMakeStreamRedirection
{
private:
// Define static variables shared by class methods.
static StreamWriter^ buildLogStream = nullptr;
static Mutex^ logMutex = gcnew Mutex;
static int maxLogLines = 25;
static int currentLogLines = 0;
public:
static void RedirectNMakeCommandStreams()
{
String^ nmakeArguments = nullptr;
Process^ nmakeProcess;
// Get the input nmake command-line arguments.
Console::WriteLine( "Enter the NMake command line arguments (@commandfile or /f makefile, etc):" );
String^ inputText = Console::ReadLine();
if ( !String::IsNullOrEmpty( inputText ) )
{
nmakeArguments = inputText;
}
Console::WriteLine( "Enter max line limit for log file (default is 25):" );
inputText = Console::ReadLine();
if ( !String::IsNullOrEmpty( inputText ) )
{
if ( !Int32::TryParse( inputText, maxLogLines ) )
{
maxLogLines = 25;
}
}
Console::WriteLine( "Output beyond {0} lines will be ignored.",
maxLogLines.ToString() );
// Initialize the process and its StartInfo properties.
nmakeProcess = gcnew Process;
nmakeProcess->StartInfo->FileName = "NMake.exe";
// Build the nmake command argument list.
if ( !String::IsNullOrEmpty( nmakeArguments ) )
{
nmakeProcess->StartInfo->Arguments = nmakeArguments;
}
// Set UseShellExecute to false for redirection.
nmakeProcess->StartInfo->UseShellExecute = false;
// Redirect the standard output of the nmake command.
// Read the stream asynchronously using an event handler.
nmakeProcess->StartInfo->RedirectStandardOutput = true;
nmakeProcess->OutputDataReceived += gcnew DataReceivedEventHandler( NMakeOutputDataHandler );
// Redirect the error output of the nmake command.
nmakeProcess->StartInfo->RedirectStandardError = true;
nmakeProcess->ErrorDataReceived += gcnew DataReceivedEventHandler( NMakeErrorDataHandler );
logMutex->WaitOne();
currentLogLines = 0;
// Write a header to the log file.
String^ buildLogFile = "NmakeCmd.Txt";
try
{
buildLogStream = gcnew StreamWriter( buildLogFile,true );
}
catch ( Exception^ e )
{
Console::WriteLine( "Could not open output file {0}", buildLogFile );
Console::WriteLine( "Exception = {0}", e->ToString() );
Console::WriteLine( e->Message->ToString() );
buildLogStream = nullptr;
}
if ( buildLogStream != nullptr )
{
Console::WriteLine( "Nmake output logged to {0}", buildLogFile );
buildLogStream->WriteLine();
buildLogStream->WriteLine( DateTime::Now.ToString() );
if ( !String::IsNullOrEmpty( nmakeArguments ) )
{
buildLogStream->Write( "Command line = NMake {0}", nmakeArguments );
}
else
{
buildLogStream->Write( "Command line = Nmake" );
}
buildLogStream->WriteLine();
buildLogStream->Flush();
logMutex->ReleaseMutex();
// Start the process.
Console::WriteLine();
Console::WriteLine( "\nStarting Nmake command" );
Console::WriteLine();
nmakeProcess->Start();
// Start the asynchronous read of the output stream.
nmakeProcess->BeginOutputReadLine();
// Start the asynchronous read of the error stream.
nmakeProcess->BeginErrorReadLine();
// Let the nmake command run, collecting the output.
nmakeProcess->WaitForExit();
nmakeProcess->Close();
buildLogStream->Close();
logMutex->Dispose();
}
}
private:
static void NMakeOutputDataHandler( Object^ sendingProcess,
DataReceivedEventArgs^ outLine )
{
// Collect the output, displaying it to the screen and
// logging it to the output file. Cancel the read
// operation when the maximum line limit is reached.
if ( !String::IsNullOrEmpty( outLine->Data ) )
{
logMutex->WaitOne();
currentLogLines++;
if ( currentLogLines > maxLogLines )
{
// Display the line to the console.
// Skip writing the line to the log file.
Console::WriteLine( "StdOut: {0}", outLine->Data->ToString() );
}
else
if ( currentLogLines == maxLogLines )
{
LogToFile( "StdOut", "<Max build log limit reached!>", true );
// Stop reading the output streams.
Process^ p = dynamic_cast<Process^>(sendingProcess);
if ( p != nullptr )
{
p->CancelOutputRead();
p->CancelErrorRead();
}
}
else
{
// Write the line to the log file.
LogToFile( "StdOut", outLine->Data, true );
}
logMutex->ReleaseMutex();
}
}
static void NMakeErrorDataHandler( Object^ sendingProcess,
DataReceivedEventArgs^ errLine )
{
// Collect the error output, displaying it to the screen and
// logging it to the output file. Cancel the error output
// read operation when the maximum line limit is reached.
if ( !String::IsNullOrEmpty( errLine->Data ) )
{
logMutex->WaitOne();
currentLogLines++;
if ( currentLogLines > maxLogLines )
{
// Display the line to the console.
// Skip writing the line to the log file.
Console::WriteLine( "StdErr: {0}", errLine->Data->ToString() );
}
else
if ( currentLogLines == maxLogLines )
{
LogToFile( "StdOut", "<Max build log limit reached!>", true );
// Stop reading the output streams.
Process^ p = dynamic_cast<Process^>(sendingProcess);
if ( p != nullptr )
{
p->CancelOutputRead();
p->CancelErrorRead();
}
}
else
{
// Write the line to the log file.
LogToFile( "StdErr", errLine->Data, true );
}
logMutex->ReleaseMutex();
}
}
static void LogToFile( String^ logPrefix, String^ logText,
bool echoToConsole )
{
// Write the specified line to the log file stream.
StringBuilder^ logString = gcnew StringBuilder;
if ( !String::IsNullOrEmpty( logPrefix ) )
{
logString->AppendFormat( "{0}> ", logPrefix );
}
if ( !String::IsNullOrEmpty( logText ) )
{
logString->Append( logText );
}
if ( buildLogStream != nullptr )
{
buildLogStream->WriteLine( "[{0}] {1}",
DateTime::Now.ToString(), logString->ToString() );
buildLogStream->Flush();
}
if ( echoToConsole )
{
Console::WriteLine( logString->ToString() );
}
}
};
namespace ProcessAsyncStreamSamples
{
class ProcessNMakeStreamRedirection
{
// Define static variables shared by class methods.
private static StreamWriter buildLogStream =null;
private static Mutex logMutex = new Mutex();
private static int maxLogLines = 25;
private static int currentLogLines = 0;
public static void RedirectNMakeCommandStreams()
{
String nmakeArguments = null;
Process nmakeProcess;
// Get the input nmake command-line arguments.
Console.WriteLine("Enter the NMake command line arguments " +
"(@commandfile or /f makefile, etc):");
String inputText = Console.ReadLine();
if (!String.IsNullOrEmpty(inputText))
{
nmakeArguments = inputText;
}
Console.WriteLine("Enter max line limit for log file (default is 25):");
inputText = Console.ReadLine();
if (!String.IsNullOrEmpty(inputText))
{
if (!Int32.TryParse(inputText, out maxLogLines))
{
maxLogLines = 25;
}
}
Console.WriteLine("Output beyond {0} lines will be ignored.",
maxLogLines);
// Initialize the process and its StartInfo properties.
nmakeProcess = new Process();
nmakeProcess.StartInfo.FileName = "NMake.exe";
// Build the nmake command argument list.
if (!String.IsNullOrEmpty(nmakeArguments))
{
nmakeProcess.StartInfo.Arguments = nmakeArguments;
}
// Set UseShellExecute to false for redirection.
nmakeProcess.StartInfo.UseShellExecute = false;
// Redirect the standard output of the nmake command.
// Read the stream asynchronously using an event handler.
nmakeProcess.StartInfo.RedirectStandardOutput = true;
nmakeProcess.OutputDataReceived += new DataReceivedEventHandler(NMakeOutputDataHandler);
// Redirect the error output of the nmake command.
nmakeProcess.StartInfo.RedirectStandardError = true;
nmakeProcess.ErrorDataReceived += new DataReceivedEventHandler(NMakeErrorDataHandler);
logMutex.WaitOne();
currentLogLines = 0;
// Write a header to the log file.
const String buildLogFile = "NmakeCmd.Txt";
try
{
buildLogStream = new StreamWriter(buildLogFile, true);
}
catch (Exception e)
{
Console.WriteLine("Could not open output file {0}", buildLogFile);
Console.WriteLine("Exception = {0}", e.ToString());
Console.WriteLine(e.Message);
buildLogStream = null;
}
if (buildLogStream != null)
{
Console.WriteLine("Nmake output logged to {0}",
buildLogFile);
buildLogStream.WriteLine();
buildLogStream.WriteLine(DateTime.Now.ToString());
if (!String.IsNullOrEmpty(nmakeArguments))
{
buildLogStream.Write("Command line = NMake {0}",
nmakeArguments);
}
else
{
buildLogStream.Write("Command line = Nmake");
}
buildLogStream.WriteLine();
buildLogStream.Flush();
logMutex.ReleaseMutex();
// Start the process.
Console.WriteLine();
Console.WriteLine("\nStarting Nmake command...");
Console.WriteLine();
nmakeProcess.Start();
// Start the asynchronous read of the error stream.
nmakeProcess.BeginErrorReadLine();
// Start the asynchronous read of the output stream.
nmakeProcess.BeginOutputReadLine();
// Let the nmake command run, collecting the output.
nmakeProcess.WaitForExit();
nmakeProcess.Close();
buildLogStream.Close();
logMutex.Dispose();
}
}
private static void NMakeOutputDataHandler(object sendingProcess,
DataReceivedEventArgs outLine)
{
// Collect the output, displaying it to the screen and
// logging it to the output file. Cancel the read
// operation when the maximum line limit is reached.
if (!String.IsNullOrEmpty(outLine.Data))
{
logMutex.WaitOne();
currentLogLines++;
if (currentLogLines > maxLogLines)
{
// Display the line to the console.
// Skip writing the line to the log file.
Console.WriteLine("StdOut: {0}", outLine.Data);
}
else if (currentLogLines == maxLogLines)
{
LogToFile("StdOut", "<Max build log limit reached!>",
true);
// Stop reading the output streams.
Process p = sendingProcess as Process;
if (p != null)
{
p.CancelOutputRead();
p.CancelErrorRead();
}
}
else
{
// Write the line to the log file.
LogToFile("StdOut", outLine.Data, true);
}
logMutex.ReleaseMutex();
}
}
private static void NMakeErrorDataHandler(object sendingProcess,
DataReceivedEventArgs errLine)
{
// Collect error output, displaying it to the screen and
// logging it to the output file. Cancel the error output
// read operation when the maximum line limit is reached.
if (!String.IsNullOrEmpty(errLine.Data))
{
logMutex.WaitOne();
currentLogLines++;
if (currentLogLines > maxLogLines)
{
// Display the error line to the console.
// Skip writing the line to the log file.
Console.WriteLine("StdErr: {0}", errLine.Data);
}
else if (currentLogLines == maxLogLines)
{
LogToFile("StdErr", "<Max build log limit reached!>",
true);
// Stop reading the output streams
Process p = sendingProcess as Process;
if (p != null)
{
p.CancelErrorRead();
p.CancelOutputRead();
}
}
else
{
// Write the line to the log file.
LogToFile("StdErr", errLine.Data, true);
}
logMutex.ReleaseMutex();
}
}
private static void LogToFile(String logPrefix,
String logText, bool echoToConsole)
{
// Write the specified line to the log file stream.
StringBuilder logString = new StringBuilder();
if (!String.IsNullOrEmpty(logPrefix))
{
logString.AppendFormat("{0}> ", logPrefix);
}
if (!String.IsNullOrEmpty(logText))
{
logString.Append(logText);
}
if (buildLogStream != null)
{
buildLogStream.WriteLine("[{0}] {1}",
DateTime.Now.ToString(), logString.ToString());
buildLogStream.Flush();
}
if (echoToConsole)
{
Console.WriteLine(logString.ToString());
}
}
}
}
' Define the namespaces used by this sample.
Imports System.Text
Imports System.IO
Imports System.Diagnostics
Imports System.Threading
Imports System.ComponentModel
Class ProcessNMakeStreamRedirection
' Define static variables shared by class methods.
Private Shared buildLogStream As StreamWriter = Nothing
Private Shared logMutex As Mutex = New Mutex()
Private Shared maxLogLines As Integer = 25
Private Shared currentLogLines As Integer = 0
Public Shared Sub RedirectNMakeCommandStreams()
Dim nmakeArguments As String = Nothing
Dim nmakeProcess As Process
' Get the input nmake command-line arguments.
Console.WriteLine("Enter the NMake command line arguments" + _
" (@commandfile or /f makefile, etc):")
Dim inputText As String = Console.ReadLine()
If Not String.IsNullOrEmpty(inputText) Then
nmakeArguments = inputText
End If
Console.WriteLine("Enter max line limit for log file (default is 25):")
inputText = Console.ReadLine()
If Not String.IsNullOrEmpty(inputText) Then
If Not Int32.TryParse(inputText, maxLogLines) Then
maxLogLines = 25
End If
End If
Console.WriteLine("Output beyond {0} lines will be ignored.", _
maxLogLines)
' Initialize the process and its StartInfo properties.
nmakeProcess = New Process()
nmakeProcess.StartInfo.FileName = "NMake.exe"
' Build the nmake command argument list.
If Not String.IsNullOrEmpty(nmakeArguments) Then
nmakeProcess.StartInfo.Arguments = nmakeArguments
End If
' Set UseShellExecute to false for redirection.
nmakeProcess.StartInfo.UseShellExecute = False
' Redirect the standard output of the nmake command.
' Read the stream asynchronously using an event handler.
nmakeProcess.StartInfo.RedirectStandardOutput = True
AddHandler nmakeProcess.OutputDataReceived, _
AddressOf NMakeOutputDataHandler
' Redirect the error output of the nmake command.
nmakeProcess.StartInfo.RedirectStandardError = True
AddHandler nmakeProcess.ErrorDataReceived, _
AddressOf NMakeErrorDataHandler
logMutex.WaitOne()
currentLogLines = 0
' Write a header to the log file.
Const buildLogFile As String = "NmakeCmd.Txt"
Try
buildLogStream = new StreamWriter(buildLogFile, true)
Catch e As Exception
Console.WriteLine("Could not open output file {0}", buildLogFile)
Console.WriteLine("Exception = {0}", e.ToString())
Console.WriteLine(e.Message)
buildLogStream = Nothing
End Try
If Not buildLogStream Is Nothing Then
Console.WriteLine("Nmake output logged to {0}", _
buildLogFile)
buildLogStream.WriteLine()
buildLogStream.WriteLine(DateTime.Now.ToString())
If Not String.IsNullOrEmpty(nmakeArguments) Then
buildLogStream.Write("Command line = NMake {0}", _
nmakeArguments)
Else
buildLogStream.Write("Command line = Nmake")
End If
buildLogStream.WriteLine()
buildLogStream.Flush()
logMutex.ReleaseMutex()
' Start the process.
Console.WriteLine()
Console.WriteLine("\nStarting Nmake command...")
Console.WriteLine()
nmakeProcess.Start()
' Start the asynchronous read of the error stream.
nmakeProcess.BeginErrorReadLine()
' Start the asynchronous read of the output stream.
nmakeProcess.BeginOutputReadLine()
' Let the nmake command run, collecting the output.
nmakeProcess.WaitForExit()
nmakeProcess.Close()
buildLogStream.Close()
logMutex.Dispose()
End If
End Sub
Private Shared Sub NMakeOutputDataHandler(sendingProcess As Object, _
outLine As DataReceivedEventArgs)
' Collect the output, displaying it to the screen and
' logging it to the output file. Cancel the read
' operation when the maximum line limit is reached.
If Not String.IsNullOrEmpty(outLine.Data) Then
logMutex.WaitOne()
currentLogLines = currentLogLines + 1
If currentLogLines > maxLogLines Then
' Display the line to the console.
' Skip writing the line to the log file.
Console.WriteLine("StdOut: {0}", outLine.Data)
Else If currentLogLines = maxLogLines Then
LogToFile("StdOut", "<Max build log limit reached!>", _
true)
' Stop reading the output streams.
Dim p As Process = sendingProcess
If Not (p Is Nothing) Then
p.CancelOutputRead()
p.CancelErrorRead()
End If
Else
' Write the line to the log file.
LogToFile("StdOut", outLine.Data, true)
End If
logMutex.ReleaseMutex()
End If
End Sub
Private Shared Sub NMakeErrorDataHandler(sendingProcess As Object, _
errLine As DataReceivedEventArgs)
' Collect the error output, displaying it to the screen and
' logging it to the output file. Cancel the error output
' read operation when the maximum line limit is reached.
If Not String.IsNullOrEmpty(errLine.Data) Then
logMutex.WaitOne()
currentLogLines = currentLogLines + 1
If currentLogLines > maxLogLines Then
' Display the line to the console.
' Skip writing the line to the log file.
Console.WriteLine("StdErr: {0}", errLine.Data)
Else If currentLogLines = maxLogLines Then
LogToFile("StdErr", "<Max build log limit reached!>", _
true)
' Stop reading the output streams.
Dim p As Process = sendingProcess
If Not (p Is Nothing) Then
p.CancelOutputRead()
p.CancelErrorRead()
End If
Else
' Write the line to the log file.
LogToFile("StdErr", errLine.Data, true)
End If
logMutex.ReleaseMutex()
End If
End Sub
Private Shared Sub LogToFile(logPrefix As String, _
logText As String, _
echoToConsole As String)
' Write the specified line to the log file stream.
Dim logString As StringBuilder = New StringBuilder()
If Not String.IsNullOrEmpty(logPrefix) Then
logString.AppendFormat("{0}> ", logPrefix)
End If
If Not String.IsNullOrEmpty(logText) Then
logString.Append(logText)
End If
If Not buildLogStream Is Nothing Then
buildLogStream.WriteLine("[{0}] {1}", _
DateTime.Now.ToString(), logString.ToString())
buildLogStream.Flush()
End If
If echoToConsole Then
Console.WriteLine(logString.ToString())
End If
End Sub
End Class
注解
BeginErrorReadLine 在流上 StandardError 启动异步读取操作。 CancelErrorRead 结束异步读取操作。
取消后，可以通过再次调用 BeginErrorReadLine 来恢复异步读取操作。
调用 CancelErrorRead时，将完成 所有 StandardError 正在进行的读取操作，然后禁用事件处理程序。 所有进一步重定向到 StandardError 的输出都将丢失。 如果通过调用 BeginErrorReadLine重新启用事件处理程序，则异步读取操作会恢复。 如果要在恢复异步读取操作之前更改事件处理程序，则必须在添加新事件处理程序之前删除现有事件处理程序：
// At this point the DataReceivedEventHandler(ErrorHandler1)
// has executed a CancelErrorRead.
// Remove the prior event handler.
process.ErrorDataReceived -=
new DataReceivedEventHandler(ErrorHandler1);
// Register a new event handler.
process.ErrorDataReceived +=
new DataReceivedEventHandler(ErrorHandler2);
// Call the corresponding BeginErrorReadLine.
process.BeginErrorReadLine();
注意
不能对重定向 StandardError 流混合异步和同步读取操作。 在异步或同步模式下打开 的重定向流 Process 后，该流上的所有进一步读取操作都必须处于同一模式。 如果取消上的 StandardError 异步读取操作，然后需要再次从流中读取，则必须使用 BeginErrorReadLine 恢复异步读取操作。 不要跟随CancelErrorRead对 的同步读取方法（如 、 ReadLine或 ReadToEnd）Read的StandardError调用。
