Vertically offset underscore \_ in paragraph

Question

I'm trying to vertically offset some underscores in a filename representation: some_file_name.ext so that the underscore is moved above the baseline. Here is what I tried def'ing:

\def\raiseunderscore#1-#2{\dimexpr\height#1#2\relax}

but I'm getting error: ! You can't use `\dimexpr' in restricted horizontal mode.

So in my notoriously fragmented competence on TeX primitives, I tried:

\def\raiseunderscore#1-#2{\leavevmode\dimexpr\height#1#2\relax}

to no avail.

How can I vertically offset the underscore character when used in normal text as _? Also, is there a way I can have this occur in all instances (globally) instead of making a macro for it?

Update: Here is what I am trying to achieve (I've changed the macro name for brevity) :

Here is a short MVE of what I've tried so far:

\documentclass{article}

\def\offsetchr#1#2{\dimexpr\height#1#2\relax}
\begin{document}

This sentence has a raised\quad\offsetchr{15pt}{\_} \quad character in the middle.

This sentence also has a raised\quad\offsetchr{2.5em}{\_} \quad character in the middle.

This sentence has a lowered\quad\offsetchr{-2.5em}{\_} \quad character in the middle.

\end{document}

Answer 1

Your example with \dimexpr is not understandable for me, so for TeX too. Of course, you cannot use \dimexpr in the typesetting material without any context.

But you can use \raise\hbox primitive construction and set the _ as an active character when the parameter of the \filename is read:

{\catcode`_13 
   \gdef_{\raise.35ex\hbox{\string_}}
}
\def\filename{\bgroup\catcode`_=13 \filenameA}
\def\filenameA#1{\tt#1\egroup}

% test:
\filename{some_file_name.ext}
 

Answer 2

If you don't need backslashes in the file names, you can do with the following:

\documentclass{article}

\ExplSyntaxOn

\NewDocumentCommand{\filename}{m}
 {
  \aldric_filename:n { #1 }
 }

\str_new:N \l_aldric_filename_str
\tl_new:N \l_aldric_filename_tl
\cs_generate_variant:Nn \tl_replace_all:Nnn { NV }

\cs_new_protected:Nn \aldric_filename:n
 {
  % stringify the file name
  \str_set:Nn \l_aldric_filename_str { #1 }
  % define a token list with it
  \tl_set:Nx \l_aldric_filename_tl { \str_use:N \l_aldric_filename_str }
  % replace all _ with a macro for a raised underscore
  \tl_replace_all:NVn \l_aldric_filename_tl \c_underscore_str { \aldric_filename_raised_us: }
  % deliver the result
  \texttt{ \tl_use:N \l_aldric_filename_tl }
 }

\cs_new_protected:Nn \aldric_filename_raised_us:
 {
  \raisebox { 0.2ex } { \c_underscore_str } % fix the parameter to suit
 }

\ExplSyntaxOff

\begin{document}

\filename{some_file_name.ext}

\filename{some_$tr@ng&_file_name.txt}

{\footnotesize\filename{some_file_name.ext}}

\end{document}