\HeaderA{Startup}{Initialization at Start of an R Session}{Startup}
\aliasA{.First}{Startup}{.First}
\methaliasA{.First.sys}{Startup}{.First.sys}
\aliasA{.OptRequireMethods}{Startup}{.OptRequireMethods}
\aliasA{.Renviron}{Startup}{.Renviron}
\aliasA{.Rprofile}{Startup}{.Rprofile}
\aliasA{Renviron}{Startup}{Renviron}
\methaliasA{Renviron.site}{Startup}{Renviron.site}
\aliasA{Rprofile}{Startup}{Rprofile}
\methaliasA{Rprofile.site}{Startup}{Rprofile.site}
\keyword{environment}{Startup}
\begin{Description}\relax
In \R, the startup mechanism is as follows.

Unless \option{--no-environ} was given on the command line, \R{}
searches for user and site files to process for setting environment
variables.  The name of the site file is the one pointed to by the
environment variable \env{R\_ENVIRON}; if this is unset or empty,
\file{\$R\_HOME/etc/Renviron.site} is used (if it exists, which it
does not in a \dQuote{factory-fresh} installation).
The user files searched for are \file{.Renviron} in the current or in
the user's home directory (in that order).
See \bold{Details} for how the files are read.

Then \R{} searches for the site-wide startup profile unless the command
line option \option{--no-site-file} was given.  The name of this file
is taken from the value of the \env{R\_PROFILE} environment variable.
If this variable is unset, the default is
\file{\$R\_HOME/etc/Rprofile.site}, which is used if it exists
(which it does not in a \dQuote{factory-fresh} installation).
This code is loaded into package \pkg{base}.  Users need to be
careful not to unintentionally overwrite objects in base, and it
is normally advisable to use \code{\LinkA{local}{local}} if code needs to be
executed: see the examples.

Then, unless \option{--no-init-file} was given, \R{} searches for a file
called \file{.Rprofile} in the current directory or in the user's
home directory (in that order) and sources it into the user
workspace.

It then loads a saved image of the user workspace from \file{.RData}
if there is one (unless \option{--no-restore-data} was specified, or
\option{--no-restore}, on the command line).

Next, if a function \code{.First} is found on the search path,
it is executed as \code{.First()}.
Finally, function \code{.First.sys()} in the \pkg{base} package is run.
This calls \code{\LinkA{require}{require}} to attach the default packages
specified by \code{\LinkA{options}{options}("defaultPackages")}.  If the
\pkg{methods} package is included, this will have been attached
earlier, by function \code{.OptRequireMethods()}, so that
namespace initializations such as those from the user workspace will
proceed correctly.

A function \code{.First} (and \code{\LinkA{.Last}{.Last}}) can be defined in
appropriate \file{.Rprofile} or \file{Rprofile.site} files or have
been saved in \file{.RData}.  If you want a different set of packages
than the default ones when you start, insert a call to
\code{\LinkA{options}{options}} in the \file{.Rprofile} or \file{Rprofile.site}
file.  For example, \code{options(defaultPackages = character())} will
attach no extra packages on startup.  Alternatively, set
\code{R\_DEFAULT\_PACKAGES=NULL} as an environment variable before
running \R.  Using \code{options(defaultPackages = "")} or
\code{R\_DEFAULT\_PACKAGES=""} enforces the R \emph{system} default.

The commands history is read from the file specified by the
environment variable \env{R\_HISTFILE} (default \file{.Rhistory})
unless \option{--no-restore-history} was specified (or
\option{--no-restore}).

The command-line flag \option{--vanilla} implies
\option{--no-site-file}, \option{--no-init-file},
\option{--no-restore} and \option{--no-environ}.
\end{Description}
\begin{Usage}
\begin{verbatim}
.First <- function() { ...... }

.Rprofile <startup file>
\end{verbatim}
\end{Usage}
\begin{Details}\relax
Note that there are two sorts of files used in startup:
\emph{environment files} which contain lists of environment variables
to be set, and \emph{profile files} which contain \R{} code.

Lines in a site or user environment file should be either comment
lines starting with \code{\#}, or lines of the form
\code{name=value}. The latter sets the environmental variable
\code{name} to \code{value}, overriding an existing value.  If
\code{value} contains an expression of the form \code{\$\{foo-bar\}}, the
value is that of the environmental variable \code{foo} if that exists
and is set to a non-empty value, otherwise \code{bar}.  (If it is of
the form \code{\$\{foo\}}, the default is \code{""}.)  This construction
can be nested, so \code{bar} can be of the same form (as in
\code{\$\{foo-\$\{bar-blah\}\}}).  Note that the braces are essential:
\code{\$HOME} will not be interpreted.

Leading and trailing white space in \code{value} are stripped.
\code{value} is processed in a similar way to a Unix shell.  In particular
the outermost level of (single or double) quotes is stripped, and
backslashes are removed except inside quotes.
\end{Details}
\begin{Note}\relax
The file \file{\$R\_HOME/etc/Renviron} is always read very early in
the start-up processing.  It contains environment variables set by \R{}
in the configure process.  Values in that file can be overriden in
site or user environment files: do not change
\file{\$R\_HOME/etc/Renviron} itself.  Note that this is distinct from
\file{\$R\_HOME/etc/Renviron.site}.
\end{Note}
\begin{SeeAlso}\relax
\code{\LinkA{.Last}{.Last}} for final actions before termination.
\code{\LinkA{commandArgs}{commandArgs}} for accessing the command line arguments.

\emph{An Introduction to R} for more command-line options: those
affecting memory management are covered in the help file for
\LinkA{Memory}{Memory}.

For profiling code, see \code{\LinkA{Rprof}{Rprof}}.
\end{SeeAlso}
\begin{Examples}
\begin{ExampleCode}
## Not run: 
# Example ~/.Renviron on Unix
R_LIBS=~/R/library
PAGER=/usr/local/bin/less

# Example .Renviron on Windows
R_LIBS=C:/R/library
MY_TCLTK=yes
TCL_LIBRARY=c:/packages/Tcl/lib/tcl8.4

# Example of .Rprofile
options(width=65, digits=5)
options(show.signif.stars=FALSE)
ps.options(horizontal=FALSE)
set.seed(1234)
.First <- function() cat("\n   Welcome to R!\n\n")
.Last <- function()  cat("\n   Goodbye!\n\n")

# Example of Rprofile.site
local({
  old <- getOption("defaultPackages")
  options(defaultPackages = c(old, "MASS"))
})

## if .Renviron contains
FOOBAR="coo\bar"doh\ex"abc\"def'"

## then we get
> cat(Sys.getenv("FOOBAR"), "\n")
coo\bardoh\exabc"def'
## End(Not run)\end{ExampleCode}
\end{Examples}

