Inconsistent behaviour of \detokenize on macro beginning with "e" or "f"

Question

I need to write to a file the unexpanded LaTeX. The macro \OuputToFile is bascially an \immediate\write18 and works fine with the following:

\OuputToFile{\detokenize{$\OuterMacro{\cXXX{X}}$}}%
\OuputToFile{\detokenize{$\OuterMacro{\dXXX{X}}$}}%

where the inner macros begin with c and d. BUT, has problems if they being with e or f. That is, the following does not yield the desired results:

\OuputToFile{\detokenize{$\OuterMacro{\eXXX{X}}$}}%
\OuputToFile{\detokenize{$\OuterMacro{\fXXX{X}}$}}%

Why is this, but more importantly how do I remedy this situation?

The output of the MWE below is

but the desired result is

Code:

\documentclass{article}
\usepackage{xparse}
\immediate\write18{printf "\n" > foo.tex }% Initialize File
\NewDocumentCommand{\OuputToFile}{%
    m% string to output
}{%
    \immediate\write18{printf 'string = "#1"' >> foo.tex }%
    \immediate\write18{printf "\n" >> foo.tex }%
}
\def\MyString{$\OuterMacro{\InnerMacro{X}}$}
\begin{document}
    Output to file: 
    \OuputToFile{\detokenize{$\OuterMacro{\cXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\dXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\eXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\fXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\gXXX{X}}$}}%
\end{document}

nothing to do with tex, try printf "\cXXX" on the commandline and compare with printf "\eXXX" why use printf rather than just writing the file directly? — David Carlisle, Nov 30 '21 at 00:31
you could use printf "%s" "\eXXX" etc which prints \eXXX or use echo instead of printf — David Carlisle, Nov 30 '21 at 00:36
Every \OuputToFile instruction generates a write to the log file of the form runsystem(printf 'string = "$\OuterMacro {\cXXX {X}}$"' >> foo.tex )...disabled (restricted). Do I need to enable something? — Mico, Nov 30 '21 at 00:40
(there's also tex core - How can I open a file in "append" mode? - TeX - LaTeX Stack Exchange, as well as solutions that handle everything in memory) — user202729, Nov 30 '21 at 01:02

score 12 · Accepted Answer · edited Nov 30 '21 at 12:49

This is nothing to do with TeX, \e is a control character to printf.

If you try

printf "\cXXX"

on the command line you get \cXXX

But if you try

printf "\eXXX"

you get nothing.

You could use

echo -n "\eXXX"

or

printf "%s" "\eXXX"

both of which yield \eXXX, so ...

\documentclass{article}
\usepackage{xparse}
\immediate\write18{printf "\n" > foo.tex }% Initialize File
\makeatletter
\NewDocumentCommand{\OuputToFile}{%
    m% string to output
}{%
    \immediate\write18{printf '@percentchar s' 'string = "#1"' >> foo.tex }%
    \immediate\write18{printf "\n" >> foo.tex }%
}
\makeatother
\def\MyString{$\OuterMacro{\InnerMacro{X}}$}
\begin{document}
    Output to file: 
    \OuputToFile{\detokenize{$\OuterMacro{\cXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\dXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\eXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\fXXX{X}}$}}%
    \OuputToFile{\detokenize{$\OuterMacro{\gXXX{X}}$}}%
\end{document}

produces a foo.tex


string = "$\OuterMacro {\cXXX {X}}$"
string = "$\OuterMacro {\dXXX {X}}$"
string = "$\OuterMacro {\eXXX {X}}$"
string = "$\OuterMacro {\fXXX {X}}$"
string = "$\OuterMacro {\gXXX {X}}$"

Inconsistent behaviour of \detokenize on macro beginning with "e" or "f"

Code:

1 Answers1