I have a macro which uses \typeout to print messages. I would like to unescape these.
\newcommand{\mymessage}[1]{
\typeout{#1}
}
Then \mymessage{foo\#bar} should print foo#bar. Right now it prints foo\#bar.
Edit:
Answers below show how to solve the specific problem of unescaping \# character. However, this was meant as an example only. I also need to unescape \% and any other such combination.
Edit to follow up on OP's modifications.
Perhaps this will be ok with your yet to be precisely specified yet unknown constraints:
\documentclass{article}
\newcommand{\mymessage}[1]{\bgroup\escapechar-1 \typeout{\detokenize{#1}}\egroup}
\begin{document}
\mymessage{foo\#bar\!foo\%hello\&world}
\end{document}
produces:
foo#bar!foo%hello&world
original answer
If you are not using \mymessage from inside macros, you could try
\documentclass{article}
\newcommand{\mymessage}{\bgroup\lccode`~=`\\\lowercase{\let~\string}%
\catcode92 13 \mynoescapemessage}
\newcommand{\mynoescapemessage}[1]{\typeout{#1}\egroup}
\begin{document}
\mymessage{foo\#bar\!foo\hello\world}
\end{document}
Produces:
foo#bar!foohelloworld
Notice that the reason the thing is a bit complicated (I could have chosen catcode 9 (aka "ignore")) is to avoid:
foo##bar
due to special treatment by TeX of # tokens.
Redefine \# (locally):
\newcommand{\mymessage}[1]{%
\begingroup\edef\#{\string##}%
\typeout{#1}%
\endgroup
}
\mymessage{foo\#bar}
The output is
foo#bar
Be careful with protecting end-of-lines in your macro definitions.
Here is how you can add escape codes:
\makeatletter
\newcommand{\mymessage}[1]{%
\begingroup\mymessage@escapes
\typeout{#1}%
\endgroup
}
\newcommand{\mymessage@escapes}{%
\edef\#{\string##}%
\let\%\@percentchar % already provided by LaTeX
\edef\{{\string{}\edef\}{\string}}%
\edef\${\string$}%
}
\mymessage{\{foo\#{bar}\%\$\}}
Also note that balanced braces need not be escaped in a \typeout.
The output is
{foo#{bar}%$}
\#. – egreg Nov 07 '15 at 10:40