Manipulation of Directories and File Permissions

Description

These functions provide a low-level interface to the computer's file system.

Usage

dir.exists(paths)
dir.create(path, showWarnings = TRUE, recursive = FALSE, mode = "0777")
Sys.chmod(paths, mode = "0777", use_umask = TRUE)
Sys.umask(mode = NA)

Arguments

Details

dir.exists checks that the paths exist (in the same sense as file.exists) and are directories.

dir.create creates the last element of the path, unless recursive = TRUE. Trailing path separators are discarded. The mode will be modified by the umask setting in the same way as for the system function mkdir. What modes can be set is OS-dependent, and it is unsafe to assume that more than three octal digits will be used. For more details see your OS's documentation on the system call mkdir, e.g. man 2 mkdir (and not that on the command-line utility of that name).

One of the idiosyncrasies of Windows is that directory creation may report success but create a directory with a different name, for example dir.create("G.S.") creates ‘"G.S"’. This is undocumented, and what are the precise circumstances is unknown (and might depend on the version of Windows). Also avoid directory names with a trailing space.

Sys.chmod sets the file permissions of one or more files. It may not be supported on a system (when a warning is issued). See the comments for dir.create for how modes are interpreted. Changing mode on a symbolic link is unlikely to work (nor be necessary). For more details see your OS's documentation on the system call chmod, e.g. man 2 chmod (and not that on the command-line utility of that name). Whether this changes the permission of a symbolic link or its target is OS-dependent (although to change the target is more common, and POSIX does not support modes for symbolic links: BSD-based Unixes do, though).

Sys.umask sets the umask and returns the previous value: as a special case mode = NA just returns the current value. It may not be supported (when a warning is issued and "0" is returned). For more details see your OS's documentation on the system call umask, e.g. man 2 umask.

How modes are handled depends on the file system, even on Unix-alikes (although their documentation is often written assuming a POSIX file system). So treat documentation cautiously if you are using, say, a FAT/FAT32 or network-mounted file system.

See files for how file paths with marked encodings are interpreted.

Value

dir.exists returns a logical vector of TRUE or FALSE values (without names).

dir.create and Sys.chmod return invisibly a logical vector indicating if the operation succeeded for each of the files attempted. Using a missing value for a path name will always be regarded as a failure. dir.create indicates failure if the directory already exists. If showWarnings = TRUE, dir.create will give a warning for an unexpected failure (e.g., not for a missing value nor for an already existing component for recursive = TRUE).

Sys.umask returns the previous value of the umask, as a length-one object of class "octmode": the visibility flag is off unless mode is NA.

See also the section in the help for file.exists on case-insensitive file systems for the interpretation of path and paths.

Author(s)

Ross Ihaka, Brian Ripley

See Also

file.info, file.exists, file.path, list.files, unlink, basename, path.expand.

Examples

## Not run: 
## Fix up maximal allowed permissions in a file tree
Sys.chmod(list.dirs("."), "777")
f <- list.files(".", all.files = TRUE, full.names = TRUE, recursive = TRUE)
Sys.chmod(f, (file.mode(f) | "664"))

## End(Not run)