Another way to do this kind of thing is to use a \lccode trick:
\begingroup\lccode`!=`\\\lowercase{\endgroup\def\@backslashchar{!}}
This avoids any need to change catcodes thanks to the special properties of \lowercase. Compared to the \expandafter\@gobble\string method, it's a bit more flexible as you can choose the catcode of the resulting character inside your macro. Compared to a change of catcodes, you don't have to use \global because of how \lowercase interacts with \endgroup.
Here's the detail of the code. The \begingroup is here to keep the lccode changes local. The
\lccode`!=`\\
means that when lowercasing ! you will get the backslash \ (the choice of ! is arbitrary, you just need a normal character which will not appear elsewhere inside the \lowercase). The important thing is that the lowercase version of ! wille be a normal character since \lowercase doesn't change catcodes.
The code \lowercase{\endgroup\def\@backslashchar{!}} is thus equivalent to \endgroup\def\@backslashchar{\} but with \ not being special (so \ followed by } won't be interpreted as \} but as two separate entities).
At the end, the result is that you have defined \@backslashchar to be a \ with normal catcode. It can thus be used inside a \write command without causing the same problems as \ does.
This lccode trick works with all other special characters. For example if you want a space character (of course, for spaces, the macro \space works fine):
\begingroup\lccode`!=`\ \lowercase{\endgroup\def\@spacechar{!}}
If ever you break the code on two lines, just be careful with the end of lines and put a % after the \:
\begingroup\lccode`!=`\ %
\lowercase{\endgroup\def\@spacechar{!}}
You can do with the help of the verbatim command and some low level hackery:
\documentclass{article}
\usepackage{verbatim}
\newenvironment{spverbatim}
{\verbatim\splitchars}
{\endverbatim}
\newcommand{\splitchars}{%
\definesplitchar{\!}%
\definesplitchar{\.}%
\definesplitchar{\+}%
\definesplitchar{\-}%
\definesplitchar{\^}%
\definesplitchar{\;}%
}
\newcommand{\definesplitchar}[1]{%
\begingroup\lccode`~=`#1\relax
\lowercase{\endgroup\def~}{\char`#1\hspace{0pt plus 0.1pt minus 0.1pt}}%
\catcode`#1=\active
}
\begin{document}
\begin{spverbatim}
$ mylinuxcommand
!+.++++.....+++-+++-!^!^+............................................;+++-^^!--.........+++--!^!^+.++++.....+++-+++-^!^+............................................;+++-^^!--.........+++--!^!^+.++++.....+++-+++-!^!^+............................................;+++-^^!--.........+++--!^!^
$ myotherlinuxcommand
true
$ mylastcommand
"Thank you for your help"
\end{spverbatim}
\end{document}
Best Answer
Usually you change the catcode first and then read the argument. Direct after reading the argument you can close the group and end the temporary catcode change:
Normally you should keep the scope of a catcode change to a minimum. Here you might keep the group open as well.