The R Project SVN R

% File src/library/base/man/sys.source.Rd

% Part of the R package, https://www.R-project.org

% Copyright 1995-2018 R Core Team

% Distributed under GPL 2 or later

\name{sys.source}

\alias{sys.source}

\title{Parse and Evaluate Expressions from a File}

\description{

  Parses expressions in the given file, and then successively evaluates

  them in the specified environment.

}

\usage{

sys.source(file, envir = baseenv(), chdir = FALSE,

           keep.source = getOption("keep.source.pkgs"),

           keep.parse.data = getOption("keep.parse.data.pkgs"),

           toplevel.env = as.environment(envir))

}

\arguments{

  \item{file}{a character string naming the file to be read from}

  \item{envir}{an \R object specifying the environment in which the

    expressions are to be evaluated.  May also be a list or an integer.

    The default value \code{NULL} corresponds to evaluation in the base

    environment.  This is probably not what you want; you should

    typically supply an explicit \code{envir} argument.}

  \item{chdir}{logical; if \code{TRUE}, the \R working directory is

    changed to the directory containing \code{file} for evaluating.}

  \item{keep.source}{logical.  If \code{TRUE}, functions keep

    their source including comments, see

    \code{\link{options}(keep.source = *)} for more details.}

  \item{keep.parse.data}{logical.  If \code{TRUE} and \code{keep.source} is

    also \code{TRUE}, functions keep parse data with their source, see

    \code{\link{options}(keep.parse.data = *)} for more details.}

  \item{toplevel.env}{an \R environment to be used as top level while

    evaluating the expressions.  This argument is useful for frameworks

    running package tests; the default should be used in other cases}

}

\details{

  For large files, \code{keep.source = FALSE} may save quite a bit of

  memory. Disabling only parse data via \code{keep.parse.data = FALSE}

  can already save a lot.

%%FIXME:  the following paragraph should be somewhere it's likely to be seen

  In order for the code being evaluated to use the correct environment

  (for example, in global assignments), source code in packages should

  call \code{\link{topenv}()}, which will return the namespace, if any,

  the environment set up by \code{sys.source}, or the global environment

  if a saved image is being used.

}

\seealso{\code{\link{source}}, and \code{\link{library}} which uses

  \code{sys.source}.

}

\examples{

## a simple way to put some objects in an environment

## high on the search path

tmp <- tempfile()

writeLines("aaa <- pi", tmp)

env <- attach(NULL, name = "myenv")

sys.source(tmp, env)

unlink(tmp)

search()

aaa

detach("myenv")

}

\keyword{file}

\keyword{utilities}