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( "*.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。