The R Project SVN R

\name{system}
\title{Invoke a System Command}
\usage{
system(command, intern = FALSE, ignore.stderr = FALSE)
.Platform
Platform()
}
\alias{system}
\alias{.Platform}
\alias{Platform}
\alias{unix}
\arguments{
\item{command}{the system command to be invoked, as a string.}
\item{intern}{a logical, indicates whether to make the output of the
command an \R object.}
\item{ignore.stderr}{a logical indicating whether error messages (written
    to \file{stderr}) should be ignored.  This probably only affects
    Unix-like systems and is ignored otherwise.}
}
\description{
    \code{system} invokes the system command specified by \code{command}.

    \code{.Platform} is a list with functions and variables as
    components.  This provides a possibility to write OS portable \R
    code.  However, this interface is still experimental.
    Currently, \code{.Platform <- Platform()} when R starts up.  This is
    even more experimental.
}
\details{If \code{intern} is \code{TRUE} then \code{popen} is used to invoke the
command and the output collected, line by line, into an \R
\code{\link{character}} vector which is returned as the value of
\code{system}.  If \code{intern}
is \code{FALSE} then the C function \code{system} is used to invoke
the command and the value returned by \code{system} is the exit
status of this function.  This function provides users with
the ability to invoke system commands on whatever platform they
are using.

\code{unix} is a \emph{deprecated} alternative, available for some
backwards compatibility reasons.
}
\examples{
# list all files in the current directory using the -F flag
\dontrun{system("ls -F")}

# t1 contains a vector of strings, each one
# representing a separate line of output from who
t1 <- system("who", TRUE)

system("ls fizzlipuzzli",TRUE,TRUE)# empty since file doesn't exist

if(.Platform$ OS.type == "Unix") {
   system.test <- function(...) { system(paste("test", ...)) == 0 }
   dir.exists <- function(dir) sapply(dir, function(d)system.test("-d", d))
   dir.exists(c(R.home(), "/tmp", "~", "/NO"))# > T T T F
}
}
\keyword{interface}
\keyword{file}
\keyword{utilities}