Source code for tail.cs

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using System;
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using System.IO;
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using System.Runtime.InteropServices;
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using System.Text;
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namespace RobvanderWoude
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```
{
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```
	class Tail
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	{
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		static int Main( string[] args )
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		{
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			try
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			{
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				// Default number of lines is 1
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				int numlines = 1;
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```
 
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```
				#region Command Line Parsing
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```
 
```
```
				string filename = string.Empty;
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				bool redirected;
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				bool set_l = false;
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				bool set_input = false;
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```
 
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```
				foreach ( string arg in args )
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				{
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					if ( arg[0] == '/' )
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					{
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						if ( arg.Length > 3 )
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						{
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							if ( arg.ToUpper( )[1] == 'L' )
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							{
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								if ( arg[2] != ':' )
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								{
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									return WriteError( "Invalid argument: " + arg );

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								}
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								try
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								{
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									if ( set_l )
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									{
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										return WriteError( "Duplicate /L argument" );

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									}
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									else
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									{
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										numlines = Convert.ToInt32( arg.Substring( 3 ) );

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										if ( numlines < 1 )
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										{
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											return WriteError( "Number of lines must be 1 or greater" );

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										}
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										set_l = true;
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									}
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								}
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								catch ( FormatException )
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								{
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									return WriteError( "Invalid number of lines: " + arg );

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								}
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							}
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						}
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						else
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```
						{
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							if ( arg == "/?" )
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```
							{
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								return WriteError( );
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							}
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							else
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```
							{
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								return WriteError( "Invalid argument: " + arg );

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							}
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						}
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					}
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					else
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```
					{
```
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						if ( set_input )
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```
						{
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							return WriteError( "Duplicate file argument" );

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						}
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						else
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```
						{
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							if ( File.Exists( arg ) )
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							{
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								filename = arg;
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							}
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							else
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```
							{
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								return WriteError( "Invalid filename: " + arg );

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							}
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							set_input = true;
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						}
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					}
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				}
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```
 
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				if ( ConsoleEx.InputRedirected )
```
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				{
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					if ( set_input )
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					{
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						return WriteError( "Use either file name or redirection, not both" );

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					}
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					else
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```
					{
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						set_input = true;
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						redirected = true;
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					}
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				}
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				else
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```
				{
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					if ( args.Length == 0 )
```
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					{
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						return WriteError( );
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					}
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					redirected = false;
```
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				}
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```
 
```
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				#endregion Command Line Parsing
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```
 
```
```
 
```
```
				int index = 0;
```

				string[] output = new string[numlines];

```
 
```
```
				if ( redirected )
```
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				{
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					// Read standard input and store the lines in a list

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					while ( Console.In.Peek( ) > -1 )
```
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					{
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						output.SetValue( Console.In.ReadLine( ), index );

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						index = ( index + 1 ) % numlines;
```
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					}
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				}
```
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				else
```
```
				{
```

					// Read the file and store the lines in an array

					Encoding enc = GetEncoding( filename );

					using ( FileStream fsi = File.Open( filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite ) )

					using ( BufferedStream bsi = new BufferedStream( fsi ) )

					using ( StreamReader sri = new StreamReader( bsi, enc ) )

```
					{
```
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						while ( sri.Peek( ) > -1 )
```
```
						{
```

							output.SetValue( sri.ReadLine( ), index );

							index = ( index + 1 ) % numlines;

```
						}
```
```
					}
```
```
				}
```
```
 
```

				// Display the lines in the correct order

				for ( int i = index; i < output.Length; i++ )

```
				{
```
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					Console.WriteLine( output[i] );
```
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				}
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```
				if ( index > 0 )
```
```
				{
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					for ( int i = 0; i < index; i++ )
```
```
					{
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						Console.WriteLine( output[i] );
```
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					}
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```
				}
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				return 0;
```
```
			}
```
```
			catch ( Exception e )
```
```
			{
```
```
				return WriteError( e.Message );
```
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			}
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		}
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```
 
```
```
 
```
```
		#region Redirection Detection
```
```
 
```

		// Code to detect redirection by Hans Passant on StackOverflow.com/a/3453272

```
		public static class ConsoleEx
```
```
		{
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			public static bool OutputRedirected
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			{
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				get
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				{
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					return FileType.Char != GetFileType( GetStdHandle( StdHandle.Stdout ) );

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				}
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			}
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			public static bool InputRedirected
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			{
```
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				get
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				{
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					return FileType.Char != GetFileType( GetStdHandle( StdHandle.Stdin ) );

```
				}
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			}
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```
 
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			public static bool ErrorRedirected
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			{
```
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				get
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				{
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					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" )]
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			private static extern FileType GetFileType( IntPtr hdl );

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```
			[DllImport( "kernel32.dll" )]
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			private static extern IntPtr GetStdHandle( StdHandle std );

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		}
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```
 
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		#endregion Redirection Detection
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```
 
```
```
 
```
```
		#region File Encoding Detection
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```
 
```

		// Code by Jason Pierce on http://stackoverflow.com/a/19283954

```
		/// <summary>
```

		/// Determines a text file's encoding by analyzing its byte order mark (BOM).

		/// Defaults to the system default when detection of the text file's endianness fails.

```
		/// </summary>
```

		/// <param name="filename">The text file to analyze.</param>

		/// <returns>The detected encoding.</returns>

		public static Encoding GetEncoding( string filename )

```
		{
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			// Read the BOM
```
```
			var bom = new byte[4];
```

			using ( var file = new FileStream( filename, FileMode.Open ) ) file.Read( bom, 0, 4 );

```
			// Analyze the BOM
```

			if ( bom[0] == 0x2b && bom[1] == 0x2f && bom[2] == 0x76 ) return Encoding.UTF7;

			if ( bom[0] == 0xef && bom[1] == 0xbb && bom[2] == 0xbf ) return Encoding.UTF8;

			if ( bom[0] == 0xff && bom[1] == 0xfe ) return Encoding.Unicode; //UTF-16LE

			if ( bom[0] == 0xfe && bom[1] == 0xff ) return Encoding.BigEndianUnicode; //UTF-16BE

			if ( bom[0] == 0 && bom[1] == 0 && bom[2] == 0xfe && bom[3] == 0xff ) return Encoding.UTF32;

```
			return Encoding.Default;
```
```
		}
```
```
 
```
```
		#endregion File Encoding Detection
```
```
 
```
```
 
```
```
		#region Error Handling
```
```
 
```

		public static int WriteError( Exception e = null )

```
		{
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			return WriteError( e == null ? null : e.Message );

```
		}
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```
 
```

		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( );
```
```
			}
```
```
 
```
```
			/*
```
```
			Tail,  Version 1.01
```

			Return the specified number of lines from the end of the specified file

```
 
```
```
			Usage:   TAIL  filename  [ option ]
```

			   or:   TAIL  [ option ]  <  filename

```
 
```

			Where:   filename   is the file to be read

			         /L:n       read the last n Lines (default: 1 line)

```
 
```
```
			Examples:
```

			TAIL  filename                 read the last line (default)

			TAIL  filename  /L:5           read the last 5 lines

			TAIL  /L:5  <  filename        read the last 5 lines

```
 
```

			Check for redirection by Hans Passant on StackOverflow.com/a/3453272

			Check file encoding by Jason Pierce on StackOverflow.com/a/19283954

```
 
```
```
			Written by Rob van der Woude
```
```
			http://www.robvanderwoude.com
```
```
			*/
```
```
 
```
```
			Console.Error.WriteLine( );
```

			Console.Error.WriteLine( "Tail,  Version 1.01" );

			Console.Error.WriteLine( "Return the specified number of lines from the end of the specified file" );

```
			Console.Error.WriteLine( );
```
```
			Console.Error.Write( "Usage:   " );
```

			Console.ForegroundColor = ConsoleColor.White;

			Console.Error.WriteLine( "TAIL  filename  [ option ]" );

```
			Console.ResetColor( );
```
```
			Console.Error.Write( "   or:   " );
```

			Console.ForegroundColor = ConsoleColor.White;

			Console.Error.WriteLine( "TAIL  [ option ]  <  filename" );

```
			Console.ResetColor( );
```
```
			Console.Error.WriteLine( );
```
```
			Console.Error.Write( "Where:   " );
```

			Console.ForegroundColor = ConsoleColor.White;

```
			Console.Error.Write( "filename" );
```
```
			Console.ResetColor( );
```

			Console.Error.WriteLine( "   is the file to be read" );

			Console.ForegroundColor = ConsoleColor.White;

			Console.Error.Write( "         /L:n" );

```
			Console.ResetColor( );
```

			Console.Error.Write( "       read the last " );

			Console.ForegroundColor = ConsoleColor.White;

```
			Console.Error.Write( "n L" );
```
```
			Console.ResetColor( );
```

			Console.Error.WriteLine( "ines (default: 1 line)" );

```
			Console.Error.WriteLine( );
```

			Console.Error.WriteLine( "Examples:" );

			Console.Error.WriteLine( "TAIL  filename                 read the last line (default)" );

			Console.Error.WriteLine( "TAIL  filename  /L:5           read the last 5 lines" );

			Console.Error.WriteLine( "TAIL  /L:5  <  filename        read the last 5 lines" );

```
			Console.Error.WriteLine( );
```

			Console.Error.Write( "Check for redirection by Hans Passant on " );

			Console.ForegroundColor = ConsoleColor.DarkGray;

			Console.Error.WriteLine( "StackOverflow.com/a/3453272" );

```
			Console.ResetColor( );
```

			Console.Error.Write( "Check file encoding by Jason Pierce on " );

			Console.ForegroundColor = ConsoleColor.DarkGray;

			Console.Error.WriteLine( "StackOverflow.com/a/19283954" );

```
			Console.ResetColor( );
```
```
			Console.Error.WriteLine( );
```

			Console.Error.WriteLine( "Written by Rob van der Woude" );

			Console.Error.WriteLine( "http://www.robvanderwoude.com" );

```
			return 1;
```
```
		}
```
```
 
```
```
		#endregion Error Handling
```
```
	}
```
```
}
```
```
 
```