% File src/library/utils/man/browseURL.Rd
% Part of the R package, https://www.R-project.org
% Copyright 1995-2018 R Core Team
% Distributed under GPL 2 or later

\name{browseURL}
\alias{browseURL}
\title{Load URL into an HTML Browser}
\description{
  Load a given URL into an HTML browser.
}
\usage{
browseURL(url, browser = getOption("browser"),
          encodeIfNeeded = FALSE)
}
\arguments{
  \item{url}{a non-empty character string giving the URL to be loaded.
   Some platforms also accept file paths.
  }
  \item{browser}{a non-empty character string giving the name of the
    program to be used as the HTML browser.  It should be in the PATH,
    or a full path specified.  Alternatively, an \R function to be
    called to invoke the browser.

    Under Windows \code{NULL} is also allowed (and is the default), and
    implies that the file association mechanism will be used.
  }
  \item{encodeIfNeeded}{Should the URL be encoded by
    \code{\link{URLencode}} before passing to the browser?  This is not
    needed (and might be harmful) if the \code{browser} program/function
    itself does encoding, and can be harmful for \samp{file://} URLs on some
    systems and for \samp{http://} URLs passed to some CGI applications.
    Fortunately, most URLs do not need encoding.}
}
\details{
  \describe{
    \item{On Unix-alikes:}{
  The default browser is set by option \code{"browser"}, in turn set by
  the environment variable \env{R_BROWSER} which is by default set in
  file \file{\var{\link{R_HOME}}/etc/Renviron} to a choice
  made manually or automatically when \R was configured.  (See
  \code{\link{Startup}} for where to override that default value.)
  To suppress showing URLs altogether, use the value \code{"false"}.
  
  On many platforms it is best to set option \code{"browser"} to a
  generic program/script and let that invoke the user's choice of
  browser.  For example, on macOS use \command{open} and on many other
  Unix-alikes use \command{xdg-open}.
  
  If \code{browser} supports remote control and \R knows how to perform
  it, the URL is opened in any already-running browser or a new one if
  necessary.  This mechanism currently is available for browsers which
  support the \code{"-remote openURL(...)"} interface (which includes
  Mozilla and Opera), Galeon, KDE konqueror (\emph{via} kfmclient) and
  the GNOME interface to Mozilla. (Firefox has dropped support, but
  defaults to using an already-running browser.)  Note that the type of
  browser is determined from its name, so this mechanism will only be
  used if the browser is installed under its canonical name.

  Because \code{"-remote"} will use any browser displaying on the X
  server (whatever machine it is running on), the remote control
  mechanism is only used if \code{DISPLAY} points to the local host.
  This may not allow displaying more than one URL at a time from a
  remote host.

  It is the caller's responsibility to encode \code{url} if necessary
  (see \code{\link{URLencode}}).

  To suppress showing URLs altogether, set \code{browser = "false"}.
  
  The behaviour for arguments \code{url} which are not URLs is
  platform-dependent.  Some platforms accept absolute file paths; fewer
  accept relative file paths.

    }
    \item{On Windows:}{
  The default browser is set by option \code{"browser"}, in turn set by
  the environment variable \env{R_BROWSER} if that is set, otherwise to
  \code{NULL}.
  To suppress showing URLs altogether, use the value \code{"false"}.

  Some browsers have required \code{:} be replaced by \code{|} in file
  paths: others do not accept that.  All seem to accept \code{\\} as a
  path separator even though the RFC1738 standard requires \code{/}.

  To suppress showing URLs altogether, set \code{browser = "false"}.
    }
  }% {describe}
}

\examples{
\dontrun{
## for KDE users who want to open files in a new tab
options(browser = "kfmclient newTab")

browseURL("https://www.r-project.org")

## On Windows-only, something like
browseURL("file://d:/R/R-2.5.1/doc/html/index.html",
          browser = "C:/Program Files/Mozilla Firefox/firefox.exe")
}}

\section{URL schemes}{
  Which URL schemes are accepted is platform-specific: expect
  \samp{http://}, \samp{https://} and \samp{ftp://} to work, but
  \samp{mailto:} may or may not (and if it does may not use the user's
  preferred email client).
  
  For the \samp{file://} scheme the format accepted (if any) can depend on
  both browser and OS.
}
\keyword{file}