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% File src/library/base/man/file.info.Rd
% Part of the R package, http://www.R-project.org
% Copyright 1995-2011 R Core Development Team
% Distributed under GPL 2 or later

\name{file.info}
\alias{file.info}
\title{Extract File Information}
\description{
  Utility function to extract information about files on the user's
  file systems.
}
\usage{
file.info(\dots)
}
\arguments{
  \item{\dots}{character vectors containing file paths.  Tilde-expansion
    is done: see \code{\link{path.expand}}.}
}
\details{
  What constitutes a \sQuote{file} is OS-dependent but includes
  directories.  (However, directory names must not include a trailing
  backslash or slash on Windows.)

  The file \sQuote{mode} follows POSIX conventions, giving three octal
  digits summarizing the permissions for the file owner, the owner's
  group and for anyone respectively.  Each digit is the logical
  \emph{or} of read (4), write (2) and execute/search (1) permissions.
  
#ifdef unix
  On most systems symbolic links are followed, so information is given
  about the file to which the link points rather than about the link.
#endif
#ifdef windows
  File modes are probably only useful on NTFS file systems, and it seems
  all three digits refer to the file's owner.
  The execute/search bits are set for directories, and for files based
  on their extensions (e.g., \file{.exe}, \file{.com}, \file{.cmd}
  and \file{.bat} files).  \code{\link{file.access}} will give a more
  reliable view of read/write access availability to the \R process.
  
  UTF-8-encoded file names not valid in the current locale can be used.
#endif
}
\value{
  A data frame with row names the file names and columns
  \item{size}{double: File size in bytes.}
  \item{isdir}{logical: Is the file a directory?}
  \item{mode}{integer of class \code{"octmode"}.  The file permissions,
    printed in octal, for example \code{644}.}
  \item{mtime, ctime, atime}{integer of class \code{"POSIXct"}:
    file modification, \sQuote{last status change} and last access times.}
#ifdef unix
  \item{uid}{integer: the user ID of the file's owner.}
  \item{gid}{integer: the group ID of the file's group.}
  \item{uname}{character: \code{uid} interpreted as a user name.}
  \item{grname}{character: \code{gid} interpreted as a group name.}
  Unknown user and group names will be \code{NA}.
#endif
#ifdef windows
  \item{exe}{character: what sort of executable is this?  Possible
    values are \code{"no"}, \code{"msdos"}, \code{"win16"},
    \code{"win32"}, \code{"win64"} and \code{"unknown"}.  Note that a
    file (e.g. a script file) can be executable according to the mode
    bits but not executable in this sense.}
#endif

  Entries for non-existent or non-readable files will be \code{NA}.
#ifdef unix
  The \code{uid}, \code{gid}, \code{uname} and \code{grname} columns
  may not be supplied on a non-POSIX Unix-alike system, and will not be
  on Windows.
#endif

  What is meant by the three file times depends on the OS and file
  system.  On Windows native file systems \code{ctime} is the file
  creation time (something which is not recorded on most Unix-alike file
  systems).  What is meant by \sQuote{file access} and hence the
  \sQuote{last access time} is system-dependent.
  
  The times are reported to an accuracy of a second.  Many file systems
  only record times in seconds, and some (e.g. modification time on FAT
  systems) are recorded in increments of 2 or more seconds.
}
#ifdef unix
\note{
  Some systems allow files of more than 2Gb to be created but
  not accessed by the \code{stat} system call.  Such files will show up
  as non-readable (and very likely not be readable by any of \R's input
  functions) -- fortunately such file systems are becoming rare.
}
#endif

\seealso{
  \code{\link{Sys.readlink}} to find out about symbolic links,
  \code{\link{files}}, \code{\link{file.access}},
  \code{\link{list.files}},
  and \code{\link{DateTimeClasses}} for the date formats.
  
  \code{\link{Sys.chmod}} to change permissions.
}
\examples{
ncol(finf <- file.info(dir()))# at least six
\dontrun{finf # the whole list}
## Those that are more than 100 days old :
finf[difftime(Sys.time(), finf[,"mtime"], units="days") > 100 , 1:4]

file.info("no-such-file-exists")
}
\keyword{file}