\documentclass[a4paper]{article}

\usepackage{listings}

\title{Extraction of the source name}
\author{Vincent Goulet and R Core Team}

\begin{document}

\maketitle

This document illustrates usage of the function
\texttt{SweaveGetSourceName}. The function may simply be used to
print the name of the file being processed by \texttt{Sweave}.
<<>>=
SweaveGetSourceName()
@

The anticipated main use of the function is to launch
\texttt{Stangle} inside \texttt{Sweave} without having to hard
code the name of the file in the \texttt{Stangle} call.
<<>>=
FILE <- SweaveGetSourceName()
Stangle(FILE, quiet = TRUE)
@

This can be used to build documents that rely on artifacts of the
\texttt{Stangle} call. For example, we can insert the tangled
script of this file into the document:
\lstinputlisting[basicstyle=\small\ttfamily,firstline=3]{%
  \Sexpr{basename(sub("Rnw$", "R", FILE))}}

\end{document}