Checks the permission of a file or a directory

Checks the permission of a file or a directory.

# S3 method for default
fileAccess(pathname, mode=0, safe=TRUE, ...)

Arguments

pathname: A character string of the file or the directory to be checked.
mode: An integer (0,1,2,4), cf. file.access().
safe: If TRUE, the permissions are tested more carefully, otherwise file.access() is used.
...: Not used.

Value

Returns an integer; 0 if the permission exists, -1 if not.

Details

In R there is file.access() for checking whether the permission of a file. Unfortunately, that function cannot be 100% trusted depending on platform used and file system queried, cf. [1].

Symbolic links

This function follows symbolic links (also on Windows) and returns a value based on the link target (rather than the link itself).

References

[1] R-devel thread file.access() on network (mounted) drive on Windows Vista? on Nov 26, 2008. https://stat.ethz.ch/pipermail/r-devel/2008-December/051461.html
[2] Filesystem permissions, Wikipedia, 2010. https://en.wikipedia.org/wiki/Filesystem_permissions

Author

Henrik Bengtsson

Examples

# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# Current directory
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
path <- "."

# Test for existence
print(fileAccess(path, mode=0))
#> [1] 0
# Test for execute permission
print(fileAccess(path, mode=1))
#> [1] 0
# Test for write permission
print(fileAccess(path, mode=2))
#> [1] 0
# Test for read permission
print(fileAccess(path, mode=4))
#> [1] 0


# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# A temporary file
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
pathname <- tempfile()
cat(file=pathname, "Hello world!")

# Test for existence
print(fileAccess(pathname, mode=0))
#> [1] 0
# Test for execute permission
print(fileAccess(pathname, mode=1))
#> [1] -1
# Test for write permission
print(fileAccess(pathname, mode=2))
#> [1] 0
# Test for read permission
print(fileAccess(pathname, mode=4))
#> [1] 0

file.remove(pathname)
#> [1] TRUE


# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# The 'base' package directory
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
path <- system.file(package="base")

# Test for existence
print(fileAccess(path, mode=0))
#> [1] 0
# Test for execute permission
print(fileAccess(path, mode=1))
#> [1] 0
# Test for write permission
print(fileAccess(path, mode=2))
#> [1] -1
# Test for read permission
print(fileAccess(path, mode=4))
#> [1] 0


# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
# The 'base' package DESCRIPTION file
# - - - - - - - - - - - - - - - - - - - - - - - - - - - -
pathname <- system.file("DESCRIPTION", package="base")

# Test for existence
print(fileAccess(pathname, mode=0))
#> [1] 0
# Test for execute permission
print(fileAccess(pathname, mode=1))
#> [1] -1
# Test for write permission
print(fileAccess(pathname, mode=2))
#> [1] -1
# Test for read permission
print(fileAccess(pathname, mode=4))
#> [1] 0