\name{capabilities}
\alias{capabilities}
\title{Report Capabilities of this Build of R}
\description{
  Report on the optional features which have been compiled into this
  build of \R.
}
\usage{
capabilities(what = NULL)
}
\arguments{
  \item{what}{character vector or \code{NULL}, specifying
    required components.  \code{NULL} implies that all are required.}
}
\value{
  A named logical vector. Current components are
    \item{jpeg}{Is the \code{\link{jpeg}} function operational?}
    \item{png}{Is the \code{\link{png}} function operational?}
    \item{tcltk}{Is the \pkg{tcltk} package operational?}
    \item{X11}{(Unix)  Are \code{X11} and the data editor available?}
    \item{GNOME}{(Unix)  Is the GNOME GUI in use and are \code{GTK} and
      \code{GNOME} graphics devices available?}
    \item{libz}{Is \code{\link{gzfile}} available?  From \R 1.5.0 this
      will always be true.}
    \item{http/ftp}{Are \code{\link{url}} and the internal method for
      \code{\link{download.file}} available?}
    \item{sockets}{Are \code{\link{make.socket}} and related functions
      available?}
    \item{libxml}{Is there support for integrating \code{libxml} with
      the \R event loop?}
    \item{cledit}{Is command-line editing available in the current \R
      session?  This is false in non-interactive sessions.
#ifdef unix
      It will be true if \code{readline} supported has been compiled in
      and \option{--no-readline} was \emph{not} invoked.
#endif
      }
    \item{IEEE754}{Does this platform have IEEE 754 arithmetic?  Note
      that this is more correctly known by the international standard
      IEC 60559, and will always be true from \R version 2.0.0.}
    \item{bzip2}{Is \code{\link{bzfile}} available?}
    \item{PCRE}{Is the Perl-Compatible Regular Expression library
      available?  This is needed for the \code{perl = TRUE} option to
      \code{\link{grep}} are related function.}
}
\seealso{\code{\link{.Platform}}}

\examples{
capabilities()

if(!capabilities("http/ftp"))
   warning("internal download.file() is not available")

## See also the examples for 'connections'.
}
\keyword{utilities}
