How to pass arguments to a "Verbatim" environment from a variable?

Question

The arguments that I need to pass to a Verbatim environment are in a variable. I'm trying to do this:

\documentclass{article}
\usepackage{fancyvrb}
\begin{document}
\def\opts{numbers=left}
\begin{Verbatim}[\opts]
Hello, world!
\end{Verbatim}
\end{document}

Obviously, t fails:

! Package keyval Error: numbers=left undefined.
See the keyval package documentation for explanation.
Type  H <return>  for immediate help.
 ...
l.5 \begin{Verbatim}[\opts]

What is the right way?

score 5 · Accepted Answer · answered Jan 09 '24 at 15:43

You generally don't want to pass a macro for options, but to define a new key.

\documentclass{article}
\usepackage{fancyvrb}
\makeatletter
\define@key{FV}{opts}[]{%
  \setkeys{FV}{
    numbers=left,
    % additional options
  }%
}
\makeatother
\begin{document}
\begin{Verbatim}[opts]
Hello, world!
\end{Verbatim}
\end{document}

If you insist in passing macros, you need to expand them prior the environment parses them.

\documentclass{article}
\usepackage{fancyvrb}
\newcommand{\opts}{numbers=left}
\begin{document}
\expanded{\noexpand\begin{Verbatim}[\opts]}
Hello, world!
\end{Verbatim}
\end{document}

But I can't recommend this.

Another strategy is to define a new Verbatim:

\documentclass{article}
\usepackage{fancyvrb}
\DefineVerbatimEnvironment{lVerbatim}{Verbatim}{numbers=left}
\begin{document}
\begin{lVerbatim}
Hello, world!
\end{lVerbatim}
\end{document}

I define my options in a few steps, setting it once and then adding more elements to it, according to some configuration requirements. In the end I have a variable \opts where all keys are accumulated. Is it possible to do the same with the key you recommended? Can you please illustrate how exactly? — yegor256, Jan 09 '24 at 15:47

score 2 · Answer 2 · answered Jan 09 '24 at 15:32

You need to expand \opts prior to the invocation of Verbatim. Here is one way it can be done.

\documentclass{article}
\usepackage{fancyvrb}
\begin{document}
\def\opts{numbers=left}
\def\z{\begin{Verbatim}}
\expandafter\z\expandafter[\opts]
Hello, world!
\end{Verbatim}
\end{document}

How to pass arguments to a "Verbatim" environment from a variable?

2 Answers2