% File src/library/base/man/locales.Rd
% Part of the R package, http://www.R-project.org
% Copyright 1995-2008 R Core Development Team
% Distributed under GPL 2 or later

\name{locales}
\alias{locales}
\alias{Sys.getlocale}
\alias{Sys.setlocale}
\alias{LC_ALL}
\alias{LC_COLLATE}
\alias{LC_CTYPE}
\alias{LC_MONETARY}
\alias{LC_NUMERIC}
\alias{LC_TIME}

#ifdef unix
\alias{LC_MESSAGES}
\alias{LC_PAPER}
\alias{LC_MEASUREMENT}
#endif

\title{Query or Set Aspects of the Locale}
\description{
  Get details of or set aspects of the locale for the \R process.
}
\usage{
Sys.getlocale(category = "LC_ALL")
Sys.setlocale(category = "LC_ALL", locale = "")
}
\arguments{
  \item{category}{character string.  The following categories should
    always be supported: \code{"LC_ALL"},
    \code{"LC_COLLATE"}, \code{"LC_CTYPE"}, \code{"LC_MONETARY"},
    \code{"LC_NUMERIC"} and \code{"LC_TIME"}.  Some systems
#ifdef windows
    (not Windows)
#endif
    will also support \code{"LC_MESSAGES"}, \code{"LC_PAPER"}
    and \code{"LC_MEASUREMENT"}.
  }
  \item{locale}{character string.  A valid locale name on the system in
    use.  Normally \code{""} (the default) will pick up the default
    locale for the system.}
}
\details{
  The locale describes aspects of the internationalization of a program.
  Initially most aspects of the locale of \R are set to \code{"C"} (which
  is the default for the C language and reflects North-American usage).
  \R sets \code{"LC_CTYPE"} and \code{"LC_COLLATE"}, which allow the
  use of a different character set and alphabetic
  comparisons in that character set (including the use of
  \code{\link{sort}}), \code{"LC_MONETARY"} (for use by
  \code{\link{Sys.localeconv}}) and \code{"LC_TIME"} may affect
  the behaviour of \code{\link{as.POSIXlt}} and \code{\link{strptime}}
  and functions which use them (but not \code{\link{date}}).

  \R can be built with no support for locales, but it is normally
  available on Unix and is available on Windows.

  The first seven categories described here are those specified by
  POSIX.  \code{"LC_MESSAGES"} will be \code{"C"} on systems that do not
  support message translation, and is not supported on Windows.  Trying
  to use an unsupported category is an error for \code{Sys.setlocale}.

  Note that setting \code{"LC_ALL"} sets only \code{"LC_COLLATE"},
  \code{"LC_CTYPE"}, \code{"LC_MONETARY"} and \code{"LC_TIME"}.

  Attempts to set an invalid locale are ignored.  There may or may not
  be a warning, depending on the OS.

  Attempts to change the character set (by
  \code{Sys.setlocale("LC_TYPE", )}, if that implies a different
  character set) during a session may not work and are likely to lead to
  some confusion.
}
\value{
  A character string of length one describing the locale in use (after
  setting for \code{Sys.setlocale}), or an empty character string if the
  current locale settings are invalid or \code{NULL} if locale
  information is unavailable.

  For \code{category = "LC_ALL"} the details of the string are
  system-specific: it might be a single locale name or a set of locale
  names separated by \code{"/"} (Solaris, Mac OS X) or \code{";"}
  (Windows, Linux).  For portability, it is best to query categories
  individually: it is not necessarily the case that the result of
  \code{foo <- Sys.getlocale()} can be used in
  \code{Sys.setlocale("LC_ALL", locale = foo)}.
}
% assume this just affects strtod/atof, scanf/printf and friends,
% as seems to be the case in glibc.
\section{Warning}{
  Setting \code{"LC_NUMERIC"} may cause \R to function
  anomalously, so gives a warning.  Input conversions
  in \R itself are unaffected, but the reading and writing of ASCII
  \code{\link{save}} files will be, as may packages.
#ifdef unix
  Setting it temporarily to produce graphical or text output may work
  well enough, but \code{\link{options}(OutDec)} is often preferable.
#endif
#ifdef windows
  Almost all the output routines used by \R itself under Windows ignore
  the setting of \code{"LC_NUMERIC"} since they make use of the Trio
  library which is not internationalized.
#endif
}

\note{
  Changing the values of locale categories whilst \R is running ought
  to be noticed by the OS services, and usually is: one known exception
  is collation on Mac OS X which always uses the setting from the start
  of the session.
}

\seealso{
  \code{\link{strptime}} for uses of \code{category = "LC_TIME"}.
  \code{\link{Sys.localeconv}} for details of numerical and monetary
  representations.

  \code{\link{l10n_info}} gives some summary facts about the locale and
  its encoding.
}
\examples{
Sys.getlocale()
Sys.getlocale("LC_TIME")
\dontrun{
Sys.setlocale("LC_TIME", "de")     # Solaris: details are OS-dependent
Sys.setlocale("LC_TIME", "de_DE.utf8")  # Modern Linux etc.
Sys.setlocale("LC_TIME", "de_DE")  # Mac OS X
Sys.setlocale("LC_TIME", "German") # Windows
}
Sys.getlocale("LC_PAPER")          # may or may not be set

Sys.setlocale("LC_COLLATE", "C")   # turn off locale-specific sorting
}
\keyword{utilities}
