// Copy input file to output file, with line numbering.
// If no output file, use standard output.

import java.io.*;

public class NumberLines
{
    public static void main( String [ ] args )
    {
        PrintWriter   fileOut = null;
        BufferedReader fileIn = null;

        try
        {
            if( args.length == 1 )
                fileOut = new PrintWriter( System.out );
            else if ( args.length == 0 || args.length > 2 )
            {
                System.out.println( "Usage: java NumberLines sourceFile destFile" );
                return;
            }
            else if ( args[ 0 ].equals( args[ 1 ] ) )
            {
                System.out.println( "Cannot copy to self" );
                return;
            }
            else
                fileOut = new PrintWriter( new BufferedWriter(
                                     new FileWriter( args[ 1 ] ) ) );

            fileIn  = new BufferedReader( new FileReader( args[ 0 ] ) );

            String oneLine;
            int lineNum = 0;

            while( ( oneLine = fileIn.readLine( ) ) != null )
            {
                fileOut.print( ++lineNum + "\t");
                fileOut.println( oneLine );
            }
        }
        catch( IOException e )
          { e.printStackTrace( ); }

        finally
        {
            try
            {
                if( fileIn != null )
                    fileIn.close( );
            }
            catch( IOException e )
              { e.printStackTrace( ); }

            try
            {
                if( fileOut != null )
                    ((Writer)fileOut).close( );
            }
            catch( IOException e )
              { e.printStackTrace( ); }
        }
    }
}