modify default underscore behaviour/interpretation

Question

Is there any way to modify the default in-text underscore behaviour document-wide?

I'm utilising a lot of filenames, IDs and so on which often have underscores in, and LaTeX doesn't like this (missing $ inserted....). Its becoming laborious to change these every time. Can I do something to resolve this once and for all document-wide without breaking anything?

Answer 1

Use

\catcode`_=12

and then use \sb to get subscripts in math

\documentclass{article}

\usepackage[T1]{fontenc}

\catcode`_=12

\begin{document}

This is a_document_with_underscores and _mathematics_ $x\sb{2}$
\end{document}

Answer 2

You can use _ as subscript prefix in math mode and the same _ as normal character outside math mode. Try this:

\catcode`\_=13  \let_=\sb
\mathcode`\_="8000
\catcode`\_=12