"verbwithin"----File ended while scanning use of \@xverbatim’,

Why doesn’t verbatim work within …?

The LaTeX verbatim commands work by changing category codes. Knuthsays of this sort of thing “Some care is needed to get the timingright…”, since once the category code has been assigned to acharacter, it doesn’t change. So \verb and\begin{verbatim} have to assume that they are getting thefirst look at the parameter text; if they aren’t, TeX has alreadyassigned category codes so that the verbatim command doesn’t have achance. For example:

\verb+\error+

will work (typesetting ‘\error’), but

\newcommand{\unbrace}[1]{#1}\unbrace{\verb+\error+}

will not (it will attempt to execute \error). Other errors onemay encounter are ‘\verb ended by end of line’, or even therather more helpful ‘\verb illegal in command argument’. Thesame sorts of thing happen with \begin{verbatim} …\end{verbatim}:

\ifthenelse{\boolean{foo}}{%\begin{verbatim}foobar\end{verbatim}}{%\begin{verbatim}barfoo\end{verbatim}}

provokes errors like ‘File ended while scanning use of\@xverbatim’, as \begin{verbatim} fails to see itsmatching \end{verbatim}.

This is why the LaTeX book insists that verbatimcommands must not appear in the argument of any other command; theyaren’t just fragile, they’re quite unusable in any command parameter,regardless of \protection. (The \verbcommand tries hard to detect if you’re misusing it; unfortunately, itcan’t always do so, and the error message is therefore not a reliableindication of problems.)

The first question to ask yourself is: “is \verb actuallynecessary?”.

• If \texttt{your text} produces the same result as \verb+your text+, then there’s no need of \verb in the first place.
• If you’re using \verb to typeset a URL or email address or the like, then the \url command from the url will help: it doesn’t suffer from all the problems of \verb, though it’s still not robust; “typesetting URLs” offers advice here.
• If you’re putting \verb into the argument of a boxing command (such as \fbox), consider using the lrbox environment:

  \newsavebox{\mybox}    ...    \begin{lrbox}{\mybox}    \verb!VerbatimStuff!    \end{lrbox}    \fbox{\usebox{\mybox}}    

Otherwise, there are three partial solutions to the problem.

• Some packages have macros which are designed to be responsive to verbatim text in their arguments. For example, the fancyvrb package defines a command \VerbatimFootnotes, which redefines the \footnotetext command, and hence also the behaviour of the \footnote) command, in such a way that you can include \verb commands in its argument. This approach could in principle be extended to the arguments of other commands, but it can clash with other packages: for example, \VerbatimFootnotes interacts poorly with the para option of the footmisc package.

  The memoir class defines its \footnote command so that it will accept verbatim in its arguments, without any supporting package.

• The fancyvrb package defines a command \SaveVerb, with a corresponding \UseVerb command, that allow you to save and then to reuse the content of its argument; for details of this extremely powerful facility, see the package documentation.

  Rather simpler is the verbdef package, whose \verbdef command defines a (robust) command which expands to the verbatim argument given.

• If you have a single character that is giving trouble (in its absence you could simply use \texttt), consider using \string. \texttt{my\string_name} typesets the same as \verb+my_name+, and will work in the argument of a command. It won’t, however, work in a moving argument, and no amount of \protection will make it work in such a case.

  A robust alternative is:

  \chardef\us=`\_    ...    \section{... \texttt{my\us name}}    

  Such a definition is ‘naturally’ robust; the construction “<back-tick>\<char>” may be used for any troublesome character (though it’s plainly not necessary for things like percent signs for which (La)TeX already provides robust macros).