ProcessStartInfo.RedirectStandardOutput 屬性

參考

定義

命名空間:: System.Diagnostics

組件:: System.Diagnostics.Process.dll

組件:: System.dll

組件:: netstandard.dll

來源:: ProcessStartInfo.cs

來源:: ProcessStartInfo.cs

來源:: ProcessStartInfo.cs

重要

部分資訊涉及發行前產品，在發行之前可能會有大幅修改。 Microsoft 對此處提供的資訊，不做任何明確或隱含的瑕疵擔保。

取得或設定值，表示應用程式的文字輸出是否寫入至 StandardOutput 資料流。

public:
 property bool RedirectStandardOutput { bool get(); void set(bool value); };

public bool RedirectStandardOutput { get; set; }

member this.RedirectStandardOutput : bool with get, set

Public Property RedirectStandardOutput As Boolean

屬性值

Boolean

如果輸出應該寫入至 StandardOutput，則為 true，否則為 false。預設為 false。

範例

// Run "cl.exe /cld stdstr.cpp /link /out:sample.exe". UseShellExecute is false because we're specifying
// an executable directly and in this case depending on it being in a PATH folder. By setting
// RedirectStandardOutput to true, the output of cl.exe is directed to the Process.StandardOutput stream
// which is then displayed in this console window directly.    
Process^ compiler = gcnew Process;
compiler->StartInfo->FileName = "cl.exe";
compiler->StartInfo->Arguments = "/clr stdstr.cpp /link /out:sample.exe";
compiler->StartInfo->UseShellExecute = false;
compiler->StartInfo->RedirectStandardOutput = true;
compiler->Start();

Console::WriteLine( compiler->StandardOutput->ReadToEnd() );

compiler->WaitForExit();

// Run "csc.exe /r:System.dll /out:sample.exe stdstr.cs". UseShellExecute is false because we're specifying
// an executable directly and in this case depending on it being in a PATH folder. By setting
// RedirectStandardOutput to true, the output of csc.exe is directed to the Process.StandardOutput stream
// which is then displayed in this console window directly.
using (Process compiler = new Process())
{
    compiler.StartInfo.FileName = "csc.exe";
    compiler.StartInfo.Arguments = "/r:System.dll /out:sample.exe stdstr.cs";
    compiler.StartInfo.UseShellExecute = false;
    compiler.StartInfo.RedirectStandardOutput = true;
    compiler.Start();

    Console.WriteLine(compiler.StandardOutput.ReadToEnd());

    compiler.WaitForExit();
}

' Run "vbc.exe /reference:Microsoft.VisualBasic.dll /out:sample.exe stdstr.vb". UseShellExecute is False 
' because we're specifying an executable directly and in this case depending on it being in a PATH folder. 
' By setting RedirectStandardOutput to True, the output of csc.exe is directed to the Process.StandardOutput 
' stream which is then displayed in this console window directly.    
Using compiler As New Process()
    compiler.StartInfo.FileName = "vbc.exe"
    compiler.StartInfo.Arguments = "/reference:Microsoft.VisualBasic.dll /out:sample.exe stdstr.vb"
    compiler.StartInfo.UseShellExecute = False
    compiler.StartInfo.RedirectStandardOutput = True
    compiler.Start()

    Console.WriteLine(compiler.StandardOutput.ReadToEnd())

    compiler.WaitForExit()
End Using

備註

Process當將文字寫入至其標準數據流時，該文字通常會顯示在控制臺上。藉由將設定 RedirectStandardOutput 為 true 以重新導向 StandardOutput 數據流，您可以操作或隱藏進程的輸出。例如，您可以篩選文字、以不同的方式格式化，或將輸出寫入主控台和指定的記錄檔。

注意

如果您想要設定為，則必須將設定UseShellExecutefalseRedirectStandardOutput為。true 否則，從 StandardOutput 數據流讀取會擲回例外狀況。

重新導向 StandardOutput 數據流可以同步或異步讀取。、 ReadLine和 ReadToEnd 等Read方法會在行程的輸出數據流上執行同步讀取作業。這些同步讀取作業在相關聯的 Process 寫入至其 StandardOutput 數據流之前不會完成，或關閉數據流。

相反地， BeginOutputReadLine 在數據流上 StandardOutput 啟動異步讀取作業。這個方法會啟用指定的事件處理程式 (查看 OutputDataReceived 數據流輸出的) ，並立即返回呼叫端，這可以在數據流輸出導向事件處理程式時執行其他工作。

注意

正在處理異步輸出的應用程式應該呼叫 WaitForExit 方法，以確保已清除輸出緩衝區。

同步讀取作業會在從 StandardOutput 數據流讀取的呼叫端與寫入該數據流的子進程之間建立相依性。這些相依性可能會導致死結狀況。當呼叫端從子進程的重新導向數據流讀取時，它會相依於子系。呼叫端會等候讀取作業，直到子系寫入數據流或關閉數據流為止。當子進程寫入足夠的數據以填滿其重新導向的數據流時，它會相依於父代。子進程會等候下一個寫入作業，直到父系從完整數據流讀取或關閉數據流為止。當呼叫端和子進程等候彼此完成作業，而且兩者都無法繼續時，死結條件就會產生。您可以藉由評估呼叫端與子進程之間的相依性來避免死結。

本節的最後兩個範例會 Start 使用方法來啟動 名為Write500Lines.exe的可執行檔。下列範例包含其原始程式碼。

using System;
using System.IO;

public class Example3
{
   public static void Main()
   {
      for (int ctr = 0; ctr < 500; ctr++)
         Console.WriteLine($"Line {ctr + 1} of 500 written: {ctr + 1/500.0:P2}");

      Console.Error.WriteLine("\nSuccessfully wrote 500 lines.\n");
   }
}
// The example displays the following output:
//      The last 50 characters in the output stream are:
//      ' 49,800.20%
//      Line 500 of 500 written: 49,900.20%
//'
//
//      Error stream: Successfully wrote 500 lines.

Imports System.IO

Public Module Example
   Public Sub Main()
      For ctr As Integer = 0 To 499
         Console.WriteLine($"Line {ctr + 1} of 500 written: {ctr + 1/500.0:P2}")
      Next

      Console.Error.WriteLine($"{vbCrLf}Successfully wrote 500 lines.{vbCrLf}")
   End Sub
End Module
' The example displays the following output:
'      The last 50 characters in the output stream are:
'      ' 49,800.20%
'      Line 500 of 500 written: 49,900.20%
'
'
'      Error stream: Successfully wrote 500 lines.

下列範例示範如何從重新導向的數據流讀取，並等候子進程結束。此範例會藉由在之前p.WaitForExit呼叫 p.StandardOutput.ReadToEnd 來避免死結條件。如果父進程在之前p.StandardOutput.ReadToEnd呼叫 p.WaitForExit ，且子進程寫入足夠的文字以填滿重新導向數據流，則死結條件可能會產生。父進程會無限期等候子進程結束。子進程會無限期等候父系從完整 StandardOutput 數據流讀取。

using System;
using System.Diagnostics;

public class Example2
{
   public static void Main()
   {
      var p = new Process();  
      p.StartInfo.UseShellExecute = false;  
      p.StartInfo.RedirectStandardOutput = true;  
      p.StartInfo.FileName = "Write500Lines.exe";  
      p.Start();  

      // To avoid deadlocks, always read the output stream first and then wait.  
      string output = p.StandardOutput.ReadToEnd();  
      p.WaitForExit();

      Console.WriteLine($"The last 50 characters in the output stream are:\n'{output.Substring(output.Length - 50)}'");
   }
}
// The example displays the following output:
//      Successfully wrote 500 lines.
//
//      The last 50 characters in the output stream are:
//      ' 49,800.20%
//      Line 500 of 500 written: 49,900.20%
//      '

Imports System.Diagnostics'

Public Module Example
   Public Sub Main()
      Dim p As New Process()
      p.StartInfo.UseShellExecute = False  
      p.StartInfo.RedirectStandardOutput = True  
      p.StartInfo.FileName = "Write500Lines.exe"  
      p.Start() 

      ' To avoid deadlocks, always read the output stream first and then wait.  
      Dim output As String = p.StandardOutput.ReadToEnd()  
      p.WaitForExit()

      Console.WriteLine($"The last 50 characters in the output stream are:\n'{output.Substring(output.Length - 50)}'")
   End Sub
End Module
' The example displays the following output:
'      Successfully wrote 500 lines.
'
'      The last 50 characters in the output stream are:
'      ' 49,800.20%
'      Line 500 of 500 written: 49,900.20%
'      '

當您從標準輸出和標準錯誤數據流讀取所有文字時，會出現類似的問題。下列範例會在這兩個數據流上執行讀取作業。它會在數據流上 StandardError 執行異步讀取作業，以避免死結狀況。如果父行程呼叫 p.StandardOutput.ReadToEnd 後面接著 p.StandardError.ReadToEnd ，且子進程會寫入足夠的文字來填滿其錯誤數據流，則死結條件會產生。父進程會無限期等候子進程關閉其 StandardOutput 數據流。子進程會無限期等候父系從完整 StandardError 數據流讀取。

using System;
using System.Diagnostics;

public class Example
{
   public static void Main()
   {
      var p = new Process();  
      p.StartInfo.UseShellExecute = false;  
      p.StartInfo.RedirectStandardOutput = true;  
      string eOut = null;
      p.StartInfo.RedirectStandardError = true;
      p.ErrorDataReceived += new DataReceivedEventHandler((sender, e) => 
                                 { eOut += e.Data; });
      p.StartInfo.FileName = "Write500Lines.exe";  
      p.Start();  

      // To avoid deadlocks, use an asynchronous read operation on at least one of the streams.  
      p.BeginErrorReadLine();
      string output = p.StandardOutput.ReadToEnd();  
      p.WaitForExit();

      Console.WriteLine($"The last 50 characters in the output stream are:\n'{output.Substring(output.Length - 50)}'");
      Console.WriteLine($"\nError stream: {eOut}");
   }
}
// The example displays the following output:
//      The last 50 characters in the output stream are:
//      ' 49,800.20%
//      Line 500 of 500 written: 49,900.20%
//      '
//
//      Error stream: Successfully wrote 500 lines.

Imports System.Diagnostics

Public Module Example
   Public Sub Main()
      Dim p As New Process()  
      p.StartInfo.UseShellExecute = False  
      p.StartInfo.RedirectStandardOutput = True  
      Dim eOut As String = Nothing
      p.StartInfo.RedirectStandardError = True
      AddHandler p.ErrorDataReceived, Sub(sender, e) eOut += e.Data 
      p.StartInfo.FileName = "Write500Lines.exe"  
      p.Start()  

      ' To avoid deadlocks, use an asynchronous read operation on at least one of the streams.  
      p.BeginErrorReadLine()
      Dim output As String = p.StandardOutput.ReadToEnd()  
      p.WaitForExit()

      Console.WriteLine($"The last 50 characters in the output stream are:{vbCrLf}'{output.Substring(output.Length - 50)}'")
      Console.WriteLine($"{vbCrLf}Error stream: {eOut}")
   End Sub
End Module
' The example displays the following output:
'      The last 50 characters in the output stream are:
'      ' 49,800.20%
'      Line 500 of 500 written: 49,900.20%
'      '
'
'      Error stream: Successfully wrote 500 lines.

您可以使用異步讀取作業來避免這些相依性及其死結的可能性。或者，您可以建立兩個線程並在個別線程上讀取每個數據流的輸出，以避免死結狀況。

適用於

共用方式為

ProcessStartInfo.RedirectStandardOutput 屬性

定義

屬性值

範例

備註

適用於

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其他資源