File copy without expansion

Question

What is the command for file copy? I want to copy the contents of one file into another without any command expansion. In a command line driven operating system one would use

copy source target

I tried reading the contents of one file into a variable and the writing it into the target:

\CatchFileDef{\OriginalF}{\jobname.sc0}{}
\newwrite\hcOutputStreamF
\immediate\openout\hcOutputStreamF=\jobname.sc1
\immediate\write\hcOutputStreamF{\OriginalF}
\immediate\closeout\hcOutputStreamF

but it expands the TeX commands saved in the original file.

Answer 1

Here's a Plain TeX solution that uses the ε-TeX extension \readline. It copies its source to \jobname.copy.

\newread\in
\openin\in=\jobname.tex
\newwrite\out
\immediate\openout\out\jobname.copy
\endlinechar-1
\loop \unless\ifeof\in
        \readline\in to\l
        \immediate\write\out{\l}
\repeat
\immediate\closeout\out
\closein\in
\end

Answer 2

The verbatimcopy package provides the command \VerbatimCopy which seems to do exactly what you are looking for. It doesn't seem to work for "binary" (i.e., non-text) files, though.

\documentclass{scrartcl}
\pagestyle{empty}

\usepackage{verbatimcopy}
\usepackage{graphicx}

\begin{document}
  \VerbatimCopy{input.tex}{input.tmp}
  \input{input.tmp}

  % This doesn't work for binary files:
  %\VerbatimCopy{img.png}{img2.png}
  %\includegraphics{img2.png}
\end{document}

I have added a compilable example to GitHub.

Answer 3

You were very close in your original question; just replace

\immediate\write\hcOutputStreamF{\OriginalF}

with

\immediate\write\hcOutputStreamF{\unexpanded\expandafter{\OriginalF}}

and I think you'll get what you're after.

Answer 4

This one comes fairly close. The trick is to make every character non-special while copying.

\def\everythingother{%
  \count255=0
  \loop\catcode\count255=12
    \advance\count255 1
    \ifnum\count255<256 \repeat}

\newread\infile
\newwrite\outfile
\newif\ifgo

\begingroup
\obeylines
\gdef\copyfileverbatim#1#2{%
 \begingroup\everythingother
 \obeylines
 \def^^M{}
 \immediate\openin\infile=#1
  \immediate\openout\outfile=#2
  \loop
    \read\infile to\data
    \immediate\write\outfile{\data}%
    \ifeof\infile\infile\gofalse\else\gotrue\fi
    \ifgo\repeat
  \closein\infile
  \immediate\closeout\outfile
  \endgroup}
\endgroup

\copyfileverbatim{tt.in}{tt.out}
\bye

One remaining problem: any control character in the input will be copied to its TeX equivalent, so a backspace character becomes ^^H. I have no fix for that.

Answer 5

A solution in expl3, for future reference. The reading part is pretty much identical to How can I read the whole file content verbatim into a (expl3) string variable?.

%! TEX program = pdflatex
\documentclass{article}
\begin{filecontents}{source.txt}
line 1  !?#\xyz
line 2
\end{filecontents}
\ExplSyntaxOn
\ior_open:Nn \g_tmpa_ior {source.txt}
\iow_open:Nn \g_tmpa_iow {target.txt}
\ior_str_map_variable:NNn \g_tmpa_ior \l_tmpa_str {
    \iow_now:Nx \g_tmpa_iow {\l_tmpa_str}
}
\ior_close:N \g_tmpa_ior
\iow_close:N \g_tmpa_iow
\ExplSyntaxOff
\begin{document}
\end{document}

You can see the block between \ExplSyntaxOn and \ExplSyntaxOff will copy the file named source.txt to target.txt.

Note for all of the existing answers (including this one), since they use TeX primitives to read the data, trailing spaces (and possibly tabs, depends on the version) on each line will be stripped, and if the source file has no final newline it will be added. (thus binary files cannot be copied.)

---

An alternative includes using shell-escape. Refer to https://tex.stackexchange.com/a/585404/250119.