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% File src/library/base/man/sys.source.Rd
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% Part of the R package, http://www.R-project.org
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% Copyright 1995-2007 R Core Team
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% Distributed under GPL 2 or later
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\name{sys.source}
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\alias{sys.source}
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\title{Parse and Evaluate Expressions from a File}
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\description{
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  Parses expressions in the given file, and then successively evaluates
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  them in the specified environment.
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}
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\usage{
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sys.source(file, envir = baseenv(), chdir = FALSE,
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           keep.source = getOption("keep.source.pkgs"))
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}
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\arguments{
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  \item{file}{a character string naming the file to be read from}
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  \item{envir}{an \R object specifying the environment in which the
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    expressions are to be evaluated.  May also be a list or an integer.
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    The default value \code{NULL} corresponds to evaluation in the base
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    environment.  This is probably not what you want; you should
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    typically supply an explicit \code{envir} argument.}
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  \item{chdir}{logical; if \code{TRUE}, the \R working directory is
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    changed to the directory containing \code{file} for evaluating.}
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  \item{keep.source}{logical.  If \code{TRUE}, functions keep
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    their source including comments, see
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    \code{\link{options}(keep.source = *)} for more details.}
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}
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\details{
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  For large files, \code{keep.source = FALSE} may save quite a bit of
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  memory.
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%%FIXME:  the following paragraph should be somewhere it's likely to be seen
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  In order for the code being evaluated to use the correct environment
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  (for example, in global assignments), source code in packages should
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  call \code{\link{topenv}()}, which will return the namespace, if any,
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  the environment set up by \code{sys.source}, or the global environment
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  if a saved image is being used.
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}
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\seealso{\code{\link{source}}, and \code{\link{library}} which uses
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  \code{sys.source}.
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}
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\examples{
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## a simple way to put some objects in an environment
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## high on the search path
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tmp <- tempfile()
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writeLines("aaa <- pi", tmp)
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env <- attach(NULL, name = "myenv")
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sys.source(tmp, env)
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unlink(tmp)
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search()
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aaa
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detach("myenv")
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}
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\keyword{file}
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\keyword{utilities}