fileAccess: Checks the permission of a file or a directory

Description

Checks the permission of a file or a directory.

Usage

"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.

Symbolic links

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

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].

References

[1] R-devel thread file.access() on network (mounted) drive on Windows Vista? on Nov 26, 2008. [2] Filesystem permissions, Wikipedia, 2010. http://en.wikipedia.org/wiki/Filesystem_permissions

Examples

Run this code

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

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


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

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

file.remove(pathname)


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

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


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

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

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