\HeaderA{dump}{Text Representations of R Objects}{dump}
\keyword{file}{dump}
\keyword{connection}{dump}
\begin{Description}\relax
This function takes a vector of names of \R{} objects and produces
text representations of the objects on a file or connection.
A \code{dump} file can usually be \code{\LinkA{source}{source}}d into another
\R{} (or S) session.
\end{Description}
\begin{Usage}
\begin{verbatim}
dump(list, file = "dumpdata.R", append = FALSE, 
     control = "all", envir = parent.frame(), evaluate = TRUE)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{list}] character. The names of one or more \R{} objects to be dumped.
\item[\code{file}] either a character string naming a file or a
connection.  \code{""} indicates output to the console.
\item[\code{append}] if \code{TRUE}, output will be appended to
\code{file}; otherwise, it will overwrite the contents of
\code{file}.
\item[\code{control}] character vector indicating deparsing options.
See \code{\LinkA{.deparseOpts}{.deparseOpts}} for their description.
\item[\code{envir}] the environment to search for objects.
\item[\code{evaluate}] logical.  Should promises be evaluated?
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
If some of the objects named do not exist (in scope), they are
omitted, with a warning.  If \code{file} is a file and no objects
exist then no file is created.

At present \code{source}ing may not produce an identical copy of
\code{dump}ed objects. A warning is issued if it is likely that
problems will arise, for example when dumping exotic objects such
as \LinkA{environment}{environment}s and external pointers.

\code{dump} will also warn if fewer characters were written to a file
than expected, which may indicate a full or corrupt file system.

A \code{dump} file can be \code{\LinkA{source}{source}}d into another \R{} (or
perhaps S) session, but the function \code{\LinkA{save}{save}} is designed to
be used for transporting \R{} data, and will work with \R{} objects that
\code{dump} does not handle.

To produce a more readable representation of an object, use
\code{control = NULL}.  This will skip attributes, and will make other
simplifications that make \code{source} less likely to produce an
identical copy.  See \code{\LinkA{deparse}{deparse}} for details.

To deparse the internal function representation rather than displaying
the saved source, use \code{control = c("keepInteger", "quoteExpressions", 
  "showAttributes", "warnIncomplete")}.  This will lose all
formatting and comments, but may be useful in those cases where
the saved source is no longer correct.

Promises will normally only be encountered by users as a result of
lazy-loading (when the default \code{evaluate = TRUE} is essential)
and after the use of \code{\LinkA{delayedAssign}{delayedAssign}},
when \code{evaluate = FALSE} might be intended.
\end{Details}
\begin{Value}
An invisible character vector containing the names of the objects
which were dumped.
\end{Value}
\begin{Note}\relax
The \code{envir} argument was added at version 1.7.0, and changed the
default search path for named objects to include the environment from
which \code{dump} was called.

As \code{dump} is defined in the base namespace, the \pkg{base}
package will be searched \emph{before} the global environment unless
\code{dump} is called from the top level or the \code{envir} argument
is given explicitly.

To avoid the risk of a source attribute out of sync with the actual
function definition, the source attribute of a function will never 
be dumped as an attribute.
\end{Note}
\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{\LinkA{dput}{dput}}, \code{\LinkA{dget}{dget}}, \code{\LinkA{write}{write}}.\\
\code{\LinkA{save}{save}} for a more reliable way to save \R{} objects.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
x <- 1; y <- 1:10
dump(ls(patt='^[xyz]'), "xyz.Rdmped")
print(.Last.value)
unlink("xyz.Rdmped")
\end{ExampleCode}
\end{Examples}

