\Header{source}{Read R Code from a File or a Connection}
\keyword{file}{source}
\keyword{programming}{source}
\keyword{connection}{source}
\begin{Description}\relax
\code{source} causes \R{} to accept its input from the named file (the
name must be quoted). Input is read from that file until the end of
the file is reached.   \code{\Link{parse}} is used to scan the
expressions in, they are then evaluated sequentially in the chosen
environment.
\end{Description}
\begin{Usage}
\begin{verbatim}
source(file, local = FALSE, echo = verbose, print.eval = echo,
       verbose = getOption("verbose"),  prompt.echo = getOption("prompt"),
       max.deparse.length = 150, chdir = FALSE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{file}] a connection or a character string giving the name
of the file or URL to read from.
\item[\code{local}] if \code{local} is \code{FALSE}, the statements scanned
are evaluated in the user's workspace (the global environment),
otherwise in the environment calling \code{source}.
\item[\code{echo}] logical; if \code{TRUE}, each expression is printed
after parsing, before evaluation.
\item[\code{print.eval}] logical; if \code{TRUE}, the result of
\code{eval(i)} is printed for each expression \code{i}; defaults
to \code{echo}.
\item[\code{verbose}] if \code{TRUE}, more diagnostics (than just
\code{echo = TRUE}) are printed during parsing and evaluation of
input, including extra info for \bold{each} expression.
\item[\code{prompt.echo}] character; gives the prompt to be used if
\code{echo = TRUE}.
\item[\code{max.deparse.length}] integer; is used only if \code{echo} is
\code{TRUE} and gives the maximal length of the \dQuote{echo} of a
single expression.
\item[\code{chdir}] logical; if \code{TRUE}, the R working directory is
changed to the directory containing \code{file} for evaluating.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
All versions of \R{} accept input from a connection with end of line
marked by LF (as used on Unix), CRLF (as used on DOS/Windows)
or CR (as used on classic MacOS).  The final line can be incomplete, that
is missing the final EOL marker.

If \code{\Link{options}}("keep.source") is true (the default), the
source of functions is kept so they can be listed exactly as input.
This imposes a limit of 128K chars on the function size and a nesting
limit of 265.  Use \code{option(keep.source = FALSE)} when these
limits might take effect: if exceeded they generate an error.
\end{Details}
\begin{References}\relax
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988)
\emph{The New S Language}.
Wadsworth \& Brooks/Cole.
\end{References}
\begin{SeeAlso}\relax
\code{\Link{demo}} which uses \code{source};
\code{\Link{eval}}, \code{\Link{parse}} and \code{\Link{scan}};
\code{\Link{options}("keep.source")}.
\end{SeeAlso}

