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% File src/library/base/man/reg.finalizer.Rd
% Part of the R package, http://www.R-project.org
% Copyright 1995-2007 R Core Development Team
% Distributed under GPL 2 or later

\name{reg.finalizer}
\alias{reg.finalizer}
\title{Finalization of Objects}
\description{
  Registers an \R function to be called upon garbage collection of
  object or (optionally) at the end of an \R session.
}
\usage{
  reg.finalizer(e, f, onexit = FALSE)
}
\arguments{
  \item{e}{Object to finalize. Must be environment or external pointer.}
  \item{f}{Function to call on finalization. Must accept a single argument,
    which will be the object to finalize.}
  \item{onexit}{logical: should the finalizer be run if the object is
    still uncollected at the end of the \R session?}
}
\value{
  \code{NULL}.
}
\note{
  The purpose of this function is mainly to allow objects that refer to
  external items (a temporary file, say) to perform cleanup actions when
  they are no longer referenced from within \R.  This only makes sense
  for objects that are never copied on assignment, hence the restriction
  to environments and external pointers.
}
\seealso{
  \code{\link{gc}} and \code{\link{Memory}} for garbage collection and
  memory management.
}
\examples{
f <- function(e) print("cleaning....")
g <- function(x){ e <- environment(); reg.finalizer(e,f) }
g()
invisible(gc()) # trigger cleanup
}
\keyword{programming}
\keyword{environment}