\Header{update.packages}{Download Packages from CRAN}
\alias{contrib.url}{update.packages}
\alias{CRAN.packages}{update.packages}
\alias{download.packages}{update.packages}
\alias{install.packages}{update.packages}
\alias{installed.packages}{update.packages}
\alias{newerVersion}{update.packages}
\alias{old.packages}{update.packages}
\keyword{utilities}{update.packages}
\begin{Description}\relax
These functions can be used to automatically compare the version
numbers of installed packages with the newest available version on
CRAN and update outdated packages on the fly.\end{Description}
\begin{Usage}
\begin{verbatim}
update.packages(lib.loc = .lib.loc, CRAN = options("CRAN"),
                contriburl = contrib.url(CRAN),
                method = "auto", instlib = NULL,
                ask=TRUE, available=NULL, destdir=NULL)

installed.packages(lib.loc = .lib.loc)
CRAN.packages(CRAN = options("CRAN"), method = "auto",
              contriburl = contrib.url(CRAN))
old.packages(lib.loc = .lib.loc, CRAN = getOption("CRAN"),
             contriburl = contrib.url(CRAN),
             method = "auto", available = NULL)

download.packages(pkgs, destdir, available = NULL,
                  CRAN = options("CRAN"), 
                  contriburl = contrib.url(CRAN), method = "auto")
install.packages(pkgs, lib, CRAN = options("CRAN"),
                 contriburl = contrib.url(CRAN),
                 method = "auto", available = NULL, destdir = NULL)
newerVersion(a, b)
\end{verbatim}
\end{Usage}
\begin{Arguments}
\begin{ldescription}
\item[\code{lib.loc}] A character vector describing the location of R
library trees to search through (and update packages therein).
\item[\code{CRAN}] The base URL of the CRAN mirror to use, i.e., the URL of a
CRAN root such as \code{"http://cran.r-project.org"} (the default) or
its Statlib mirror, \code{"http://lib.stat.cmu.edu/R/CRAN"}.
\item[\code{contriburl}] URL of the contrib section of CRAN. Use this argument
only if your CRAN mirror is incomplete, e.g., because you burned
only the contrib section on a CD.  Overrides argument \code{CRAN}.
\item[\code{method}] Download method, see \code{\Link{download.file}}.
\item[\code{pkgs}] A character vector of the short names of
packages whose current versions should be downloaded from \code{CRAN}.
\item[\code{destdir}] Directory where downloaded packages are stored.
\item[\code{available}] List of packages available at CRAN as returned by
\code{CRAN.packages}.
\item[\code{lib,instlib}] A character string giving the library directory where to
install the packages.
\item[\code{ask}] If \code{TRUE}, ask before packages are actually downloaded
and installed.
\item[\code{a, b}] Version strings of R packages, valid seperators are
\code{.} and \code{-}.
\end{ldescription}
\end{Arguments}
\begin{Details}\relax
\code{installed.packages} scans the \file{DESCRIPTION} files of each
package found along \code{lib.loc} and returns a list of package
names, library paths and version numbers.  \code{CRAN.packages}
returns a similar list, but corresponding to packages currently
available in the contrib section of CRAN, the comprehensive R archive
network.  The current list of packages is downloaded over the internet
(or copied from a local CRAN mirror). Both functions use
\code{\Link{parse.dcf}} for parsing the description files.
\code{old.packages} compares the two lists and reports installed
packages that have newer versions on CRAN.

\code{download.packages} takes a list of package names and a
destination directory, downloads the newest versions of the package
sources and saves the in \code{destdir}.  If the list of available
packages is not given as argument, it is also directly obtained from
CRAN.  If CRAN is local, i.e., the URL starts with \code{"file:"},
then the packages are not downloaded but used directly.

The main function of the bundle is \code{update.packages}.  First a
list of all packages found in \code{lib.loc} is created and compared
with the packages available on CRAN.  Outdated packages are reported
and for each outdated package the user can specify if it should be
automatically updated.
If so, the package sources are downloaded from
CRAN and installed in the respective library path (or \code{instlib}
if specified) using the \R{} \code{\Link{INSTALL}} mechanism.

\code{install.packages} can be used to install new packages, it
takes a vector of package names and a destination library, downloads
the packages from CRAN and installs them. If the library
is omitted it defaults to the first directory in \code{.lib.loc}, with
a warning.

For \code{install.packages} and \code{update.packages}, \code{destdir}
is the directory to which packages will be downloaded. If it is
\code{NULL} (the default) a temporary directory is used, and the user
will be given the option of deleting the temporary files once the
packages are installed.

\code{newerVersion(a, b)} is a helper function that returns
\code{TRUE} when version \code{a} is newer than version \code{b}.\end{Details}
\begin{SeeAlso}\relax
\code{\Link{INSTALL}}, \code{\Link{REMOVE}},
\code{\Link{library}}, \code{\Link{.packages}},
\code{\Link{parse.dcf}}, \code{\Link{download.file}}\end{SeeAlso}

