\newcommand\bme{\newwrite\example@out\immediate\openout \example@out hello.exa}% fopen
\newcommand\hello[2][\@empty]{%
  \ifx#1\@empty%1 No option
    \def\temp@val{1 : }%
  \else% Option
     \def\temp@val{#1 : }%
  \fi%
  \immediate\write\example@out{\temp@val #2}#2}% fwrite
\newcommand\eme{\immediate\closeout\example@out}% fclose