Define an “escape underscore” environment

Question

I am writing a text document in LaTeX where I need a lot a words with underscores: foo_bar_1, more_bar_2_long_expression_3.

I know about the underscore package, but for some reason the [strings] option doesn't work for me (I get e.g. Extra \endcsname. ...oncluding Chapter~\ref{ch:summary_outlook}).

So my idea would be to define a new command or environment

\newcommand{escunderscore}[1]{...}

in which basically _ would be replaced by \_, so that I then can write \escunderscore{foo_bar_1} in my text whenever I need underscores. Is this possible and how do I do this?

Answer 1

You can do even better: say

\usepackage[T1]{fontenc}
\catcode`\_=12

in your preamble and you'll be allowed to use the underscore as a printable character anywhere (requires a T1-encoded font, so the first line). For subscripts you can then use \sb.

A command for temporary escaping the underscore can be the following:

\makeatletter
\newcommand{\escapeus}{\begingroup\@makeother\_\@escapeus}
\newcommand*{\@escapeus}[1]{#1\endgroup}
\makeatother

that, however, will not be usable in the argument of any command, because of the change in the category code (still requires a T1-encoded font).

If T1-encoded fonts are not available, something more complicated is needed:

\makeatletter
\newcommand{\escapeus}{\begingroup\@activeus\@escapeus}
\newcommand*{\@escapeus}[1]{#1\endgroup}
\begingroup\lccode`\~=`\_\relax
   \lowercase{\endgroup\def\@activeus{\catcode`\_=\active \let~\_}}
\makeatother

Again, the \escapeus command cannot be used as the argument of another command. If you really need it there's a way:

\makeatletter
\DeclareRobustCommand*{\escapeus}[1]{%
  \begingroup\@activeus\scantokens{#1\endinput}\endgroup}
\begingroup\lccode`\~=`\_\relax
   \lowercase{\endgroup\def\@activeus{\catcode`\_=\active \let~\_}}
\makeatother

Answer 2

\documentclass{article}
\usepackage{url}
\DeclareUrlCommand\UScore{\urlstyle{rm}}
\begin{document}

foo \UScore{foo_bar_1} bar

\end{document}