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Manipulation of Directories and File Permissions

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

Keywords
file
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
path

a character vector containing a single path name. Tilde expansion (see path.expand) is done.

paths

character vectors containing file or directory paths. Tilde expansion (see path.expand) is done.

showWarnings

logical; should the warnings on failure be shown?

recursive

logical. Should elements of the path other than the last be created? If true, like the Unix command mkdir -p.

mode

the mode to be used on Unix-alikes: it will be coerced by as.octmode. For Sys.chmod it is recycled along paths.

use_umask

logical: should the mode be restricted by the umask setting?

Details

dir.create creates the last element of the path, unless recursive = TRUE. Trailing path separators are discarded. On Windows drives are allowed in the path specification and unless the path is rooted, it will be interpreted relative to the current directory on that drive. mode is ignored on Windows. 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). The interpretation of mode in the Windows system functions is non-POSIX and only supports setting the read-only attribute of the file. So R interprets mode to mean set read-only if and only if (mode & 0200) == 0 (interpreted in octal). Windows has a much more extensive system of file permissions on some file systems (e.g., versions of NTFS) which are unrelated to this system call.

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. All files on Windows are regarded as readable, and files being executable is not a Windows concept. So umask only controls whether a file is writable: a setting of "200" makes files (but not directories) created subsequently read-only.

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.

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.

Note

There is no guarantee that these functions will handle Windows relative paths of the form d:path: try d:./path instead. In particular, d: is not recognized as a directory. Nor are \\?\ prefixes (and similar) supported.

UTF-8-encoded dirnames not valid in the current locale can be used.

See Also

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

Aliases
  • dir.create
  • dir.exists
  • Sys.chmod
  • Sys.umask
  • umask
Examples
library(base) # 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.info(f)$mode | "664")) # }
Documentation reproduced from package base, version 3.5.1, License: Part of R 3.5.1

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