TeX code for dumping code boxes to a common plain text file

gistfile1.tex

\newwrite\tempfile

\usepackage{verbatim}
\makeatletter
\newwrite\Code@out % temp file for writing out and reading back in for display

\newcommand\VerbSaver{\obeylines\expandafter\VerbSaverArg\noexpand}

\newcommand\VerbSaverArg[1][code.txt]{%
    \gdef\FName{xcodetempx.txt}%
    \begingroup
        \@bsphack%
        \immediate\openout\Code@out\FName%
        \let\do\@makeother\dospecials%
        \catcode`\^^M\active%
        \def\verbatim@processline{%
            \immediate\write\tempfile{\the\verbatim@line}
            \immediate\write\Code@out{\the\verbatim@line}}%
        \verbatim@start}

\def\endVerbSaver{%
    \immediate\write\tempfile{}
    \immediate\closeout\Code@out\@esphack
    \endgroup
    \verbatiminput{\FName}}

\makeatother