C#从文件或标准输入设备读取指定行的方法

本文实例讲述了C#从文件或标准输入设备读取指定行的方法。分享给大家供大家参考。具体如下：

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
 }
}

希望本文所述对大家的C#程序设计有所帮助。