C#从文件或标准输入设备读取指定行的方法

using System;using System.IO;using System.Runtime.InteropServices;using System.Text.RegularExpressions;using System.Collections.Generic;namespace RobvanderWoude{ class ReadLine {  static int Main( string[] args )  {   #region Command Line Parsing   string filename = string.Empty;   int linestart = 1;   int lineend = 2;   bool concat = false;   bool addspaces = false;   string concatchar = string.Empty;   bool skipempty = false;   bool trimlines = false;   bool numlines = false;   bool redirected;   bool set_c = false;   bool set_l = false;   bool set_s = false;   bool set_t = false;   bool set_input = false;   if ( ConsoleEx.InputRedirected )   {    set_input = true;    redirected = true;   }   else   {    if ( args.Length == 0 )    {     return WriteError( );    }    redirected = false;   }   foreach ( string arg in args )   {    if ( arg[0] == '/' )    {     try     {      switch ( arg.ToUpper( )[1] )      {       case '?':        return WriteError( );       case 'C':        if ( arg.ToUpper( ) != "/C" && arg.ToUpper( ) != "/CS" )        {         return WriteError( "Invalid command line switch " + arg );        }        concat = true;        if ( arg.ToUpper( ) == "/CS" )        {         addspaces = true;        }        if ( set_c )        {         return WriteError( "Duplicate command line argument /C*" );        }        set_c = true;        break;       case 'L':        if(arg.ToUpper( ).StartsWith( "/L:" ) && arg.Length > 3)        {         if ( arg[2] == ':' )         {          string linessel = arg.Substring( 3 );          string pattern = @"^(/-?/d+)$";          Match match = Regex.Match( linessel, pattern );          if ( match.Success )          {           linestart = Convert.ToInt32( match.Groups[1].Value );           lineend = linestart + 1;          }          else          {           pattern = @"^(/-?/d+)/./.(/-?/d+)$";           match = Regex.Match( linessel, pattern );           if ( match.Success )           {            linestart = Convert.ToInt32( match.Groups[1].Value );            lineend = Convert.ToInt32( match.Groups[2].Value ) + 1;           }           else           {            pattern = @"^(/-?/d+),(/-?/d+)$";            match = Regex.Match( linessel, pattern );            if ( match.Success )            {             // numlines is true if the second number              //specifies the number of lines instead of a line number             numlines = true;             linestart = Convert.ToInt32( match.Groups[1].Value );             lineend = Convert.ToInt32( match.Groups[2].Value );             if ( lineend < 1 )             {              return WriteError( "Invalid number of lines (" + lineend.ToString( ) + "), must be 1 or higher" );             }            }           }          }         }         else         {          return WriteError( "Invalid command line switch " + arg );         }        }        else        {         return WriteError( "Invalid command line switch " + arg );        }        if ( set_l )        {         return WriteError( "Duplicate command line argument /L" );        }        set_l = true;        break;       case 'S':        if ( arg.ToUpper( ) != "/SE" )        {         return WriteError( "Invalid command line switch " + arg );        }        skipempty = true;        if ( set_s )        {         return WriteError( "Duplicate command line argument /SE" );        }        set_s = true;        break;       case 'T':        if ( arg.ToUpper( ) != "/T" )        {         return WriteError( "Invalid command line switch " + arg );        }        trimlines = true;        if ( set_t )        {         return WriteError( "Duplicate command line argument /T" );        }        set_t = true;        break;       default:        return WriteError( "Invalid command line switch " + arg );      }     }     catch     {      return WriteError( "Invalid command line switch " + arg );     }    }    else    {     if ( set_input )     {      return WriteError( "Multiple inputs specified (file + redirection or multiple files)" );     }     if ( redirected )     {      return WriteError( "Do not specify a file name when using redirected input" );     }     else     {      filename = arg;     }    }   }   #endregion   try   {    int count = 0;    bool output = false;    string[] lines;    List<string> alllines = new List<string>( );    if ( redirected )    {     // Read standard input and store the lines in a list     int peek = 0;     do     {      alllines.Add( Console.In.ReadLine( ) );     } while ( peek != -1 );     // Convert the list to an array     lines = alllines.ToArray( );    }    else    {     // Read the file and store the lines in a list     lines = File.ReadAllLines( filename );    }    // Check if negative numbers were used, and if so,     //calculate the resulting line numbers    if ( linestart < 0 )    {     linestart += lines.Length + 1;    }    if ( lineend < 0 )    {     lineend += lines.Length + 1;    }    if ( numlines )    {     lineend += linestart;    }    // Iterate through the array of lines and display     //the ones matching the command line switches    foreach ( string line in lines )    {     string myline = line;     if ( trimlines )     {      myline = myline.Trim( );     }     bool skip = skipempty && ( myline.Trim( ) == string.Empty );     if ( !skip )     {      count += 1;      if ( count >= linestart && count < lineend )      {       if ( concat )       {        Console.Write( "{0}{1}", concatchar, myline );       }       else       {        Console.WriteLine( myline );       }       if ( addspaces )       {        concatchar = " ";       }      }     }    }   }   catch ( Exception e )   {    return WriteError( e.Message );   }   return 0;  }  #region Redirection Detection  public static class ConsoleEx  {   public static bool OutputRedirected   {    get    {     return FileType.Char != GetFileType( GetStdHandle( StdHandle.Stdout ) );    }   }   public static bool InputRedirected   {    get    {     return FileType.Char != GetFileType( GetStdHandle( StdHandle.Stdin ) );    }   }   public static bool ErrorRedirected   {    get    {     return FileType.Char != GetFileType( GetStdHandle( StdHandle.Stderr ) );    }   }   // P/Invoke:   private enum FileType { Unknown, Disk, Char, Pipe };   private enum StdHandle { Stdin = -10, Stdout = -11, Stderr = -12 };   [DllImport( "kernel32.dll" )]   private static extern FileType GetFileType( IntPtr hdl );   [DllImport( "kernel32.dll" )]   private static extern IntPtr GetStdHandle( StdHandle std );  }  #endregion  #region Error Handling  public static int WriteError( Exception e = null )  {   return WriteError( e == null ? null : e.Message );  }  public static int WriteError( string errorMessage )  {   if ( string.IsNullOrEmpty( errorMessage ) == false )   {    Console.Error.WriteLine( );    Console.ForegroundColor = ConsoleColor.Red;    Console.Error.Write( "ERROR: " );    Console.ForegroundColor = ConsoleColor.White;    Console.Error.WriteLine( errorMessage );    Console.ResetColor( );   }   Console.Error.WriteLine( );   Console.Error.WriteLine( "ReadLine, Version 0.30 beta" );   Console.Error.WriteLine( "Return the specified line(s) from a file or Standard Input" );   Console.Error.WriteLine( );   Console.Error.Write( "Usage: " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "READLINE filename [ options ]" );   Console.ResetColor( );   Console.Error.Write( " or: " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "READLINE [ options ] < filename" );   Console.ResetColor( );   Console.Error.Write( " or: " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "command | READLINE [ options ]" );   Console.ResetColor( );   Console.Error.WriteLine( );   Console.Error.Write( "Where: " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "filename" );   Console.ResetColor( );   Console.Error.WriteLine( " is the optional file to be read" );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "   command" );   Console.ResetColor( );   Console.Error.WriteLine( " is the optional command whose output is to be read" );   Console.Error.WriteLine( );   Console.Error.Write( "Options: " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "/C   C" );   Console.ResetColor( );   Console.Error.WriteLine( "oncatenate lines" );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( " /CS  C" );   Console.ResetColor( );   Console.Error.Write( "oncatenate lines with " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "S" );   Console.ResetColor( );   Console.Error.WriteLine( "paces in between" );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( " /L:n" );   Console.ResetColor( );   Console.Error.Write( " read line " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "n" );   Console.ResetColor( );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( " /L:n..m" );   Console.ResetColor( );   Console.Error.Write( " read lines " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "n" );   Console.ResetColor( );   Console.Error.Write( " through " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "m" );   Console.Error.Write( "   /L:n,m" );   Console.ResetColor( );   Console.Error.Write( "  read " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "m" );   Console.ResetColor( );   Console.Error.Write( " lines starting at line " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.WriteLine( "n" );   Console.ResetColor( );   Console.Error.WriteLine( "(negative numbers start counting from the end backwards)" );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "   /SE  S" );   Console.ResetColor( );   Console.Error.Write( "kip " );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "E" );   Console.ResetColor( );   Console.Error.WriteLine( "mpty lines" );   Console.ForegroundColor = ConsoleColor.White;   Console.Error.Write( "   /T   T" );   Console.ResetColor( );   Console.Error.WriteLine( "rim leading and trailing whitespace from lines" );   Console.Error.WriteLine( );   Console.Error.WriteLine( "Examples:" );   Console.Error.WriteLine( "READLINE file read the first non-empty line (default)" );   Console.Error.WriteLine( "READLINE file /L:2 /SE read the second non-empty line of file" );   Console.Error.WriteLine( "READLINE file /L:5..7 read lines 5..7 of file" );   Console.Error.WriteLine( "READLINE file /L:-1 read the last line of file" );   Console.Error.WriteLine( "READLINE file /L:-2..-1 read the last 2 lines of file" );   Console.Error.WriteLine( "READLINE file /L:-2,2 read the last 2 lines of file" );   Console.Error.WriteLine( );   Console.Error.Write( "Check for redirection by Hans Passant on " );   Console.ForegroundColor = ConsoleColor.DarkGray;   Console.Error.WriteLine( "StackOverflow.com" );   Console.Error.WriteLine( "/questions/3453220/how-to-detect-if-console-in-stdin-has-been-redirected" );   Console.ResetColor( );   Console.Error.WriteLine( );   Console.Error.WriteLine( "Written by Rob van der Woude" );   return 1;  }  #endregion }}