OpeningFiles

You can open files dynamically using `getline', `close', and `print EXPR > FILENAME', like:

    # assumes input file has at least 1 line, output file writeable
    function double(infilename,outfilename,    aline)
    {
      while ( (getline aline < infilename) >0 )
        print(aline aline) > outfilename;
      close(infilename);
      close(outilename);
    }