Input a file that contains special characters like "#", "_" without using external packages

Question

I know this is a weird and stupid question, but I really need to achieve this.
I have a file containing some characters like "#", "_". For example, the file is:

abc_def#gh

And I need to input (or display the file in to the pdf) to latex without using external packages like verbatim. Achieve this just using build in latex.

I need some kind of function to replace the special character or display it in \verb style without any error.

Some limitations

• I Can't Run Bash script inside latex as well. Because of -no-shell-escape.
• Can't Use external packages by \usepackage command

Answer 1

If you don't want to use LaTeX packages then the following solution needn't LaTeX at all. Only TeX primitives and Plain TeX basic macros are used here. But the solution works in LaTeX too, because the mentioned Plain TeX macros \dospecials, \obeylines and \obeyspaces are implemented in LaTeX kernel too.

\def\inputverbatim #1{\bgroup
  \def\do##1{\catcode`##1=12 }\dospecials
  \def\par{\endgraf\noindent\null}\obeylines\obeyspaces
  \tt \noindent
  \input{#1}
  \egroup
}
%%% test:
\inputverbatim {file.txt}

Answer 2

It is hard to see why you could not use \verbatiminput

but if myfile2 has

line 1
   abc_def#gh
line 3
   $$$$$$
line 5

then

\documentclass{article}
\makeatletter
\edef\qqq#1{%
\noexpand\begin{verbatim}
\noexpand\input{#1}%
@backslashchar end\string{verbatim\string}}
\makeatother
\begin{document}
\qqq{myfile2}
\end{document}

However if verbatim.sty is not available to be used,article.cls should not be available either, both are part of the core latex release. So I do not see how any latex document could work.

Answer 3

I suggest listingsutf8 package and use it like following:

\lstinputlisting[inputencoding=utf8/cp1250,frame=hnone,numbers=none,extendedchars=true]{source.txt}

The second option is to use \detokenize command like

\detokenize{abc_def\#gh}

But as you see, # must be quoted with backslash.

Answer 4

This is how I might go at it:

%-----------------------------------------------------------------
% Let's create an external text file  SomeFile.tex  which is to be 
% input verbatim:
%-----------------------------------------------------------------
\begin{filecontents*}{SomeFile.tex}
Line 1: abc_def#gh
Line 2: $$$_def#gh
Line 3: %%%_def#gh
\end{verbatim}
Line 7: bla~~~bla
\end{filecontents*}
%-----------------------------------------------------------------
\documentclass{article}
\newcommand\Exchange[2]{#2#1}
\begin{document}
Text
\Exchange{\input{SomeFile.tex}}{\begin{verbatim}}\end{verbatim}
Text
\end{document}

---

---

If you don't wish things to be typeset in typewriter-mode and just wish TeX to treat special characters like ordinary characters that shall occur within the text while typesetting as usual, you can try s.th. like this:

%-----------------------------------------------------------------
% Let's create an external text file  SomeFile.tex  which is to be 
% input:
%-----------------------------------------------------------------
\begin{filecontents*}{SomeFile.tex}
Line 1: $&#^_~%\{}
Line 2: $&#^_~%\{}
\end{filecontents*}
%-----------------------------------------------------------------
\documentclass{article}
\makeatletter
@ifdefinable\secondwhentypesetting{\protected\def\secondwhentypesetting#1#2{#2}}
\newcommand\unexpandedwhennottypesetting[1]{\noexpand\unexpandedwhennottypesetting{\unexpanded{#1}}}
\DeclareRobustCommand\myactivateasnospecial{@dblarg@myactivateasnospecial}%
\newcommand@myactivateasnospecial[2][]{%
  \begingroup\lccode\~=#2\relax
  \lowercase{\endgroup\def~}{\secondwhentypesetting\unexpandedwhennottypesetting{#1}}%
  \catcode`#2=13\relax
}%
\makeatother
\DeclareRobustCommand\TypesetFileWithSpecialsAsOrdinaryCharacters[1]{%
  \begingroup
  % switch special characters %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  \let\do=\myactivateasnospecial
  \do$%
  \do&%
  \do#%
  \do[\ifmmode\hat{}\else\textasciicircum\fi]^%
  \do[\ifmmode_\else\textunderscore\fi]_%
  \do[\ifmmode\sim\else\textasciitilde\fi]~%
  \do%%
  \do[\csname\ifmmode\else text\fi backslash\endcsname]\%
  \do{%
  \do}%
  %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  \input{#1}%
  \endgroup
}%
\begin{document}
\TypesetFileWithSpecialsAsOrdinaryCharacters{SomeFile.tex}
$$\TypesetFileWithSpecialsAsOrdinaryCharacters{SomeFile.tex}$$
\end{document}