R.utils: filePath – R documentation

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filePath

Construct the path to a file from components and expands Windows Shortcuts along the pathname from root to leaf

Description

Construct the path to a file from components and expands Windows Shortcuts along the pathname from root to leaf. This function is backward compatible with file.path() when argument removeUps=FALSE and expandLinks="none", except that a (character) NA is return if any argument is NA.

This function exists on all platforms, not only Windows systems.

Usage

## Default S3 method:
filePath(..., fsep=.Platform$file.sep, removeUps=TRUE,
  expandLinks=c("none", "any", "local", "relative", "network"), unmap=FALSE,
  mustExist=FALSE, verbose=FALSE)

Arguments

`...`	Arguments to be pasted together to a file path and then be parsed from the root to the leaf where Windows shortcut files are recognized and expanded according to argument `which` in each step.
`fsep`	the path separator to use.
`removeUps`	If `TRUE`, relative paths, for instance "foo/bar/../" are shortened into "foo/", but also "./" are removed from the final pathname, if possible.
`expandLinks`	A `character` string. If `"none"`, Windows Shortcut files are ignored. If `"local"`, the absolute target on the local file system is used. If `"relative"`, the relative target is used. If `"network"`, the network target is used. If `"any"`, first the local, then the relative and finally the network target is searched for.
`unmap`	If `TRUE`, paths on mapped Windows drives are "followed" and translated to their corresponding "true" paths.
`mustExist`	If `TRUE` and if the target does not exist, the original pathname, that is, argument `pathname` is returned. In all other cases the target is returned.
`verbose`	If `TRUE`, extra information is written while reading.

Details

If expandLinks != "none", each component, call it parent, in the absolute path is processed from the left to the right as follows: 1. If a "real" directory of name parent exists, it is followed. 2. Otherwise, if Microsoft Windows Shortcut file with name parent.lnk exists, it is read. If its local target exists, that is followed, otherwise its network target is followed. 3. If no valid existing directory was found in (1) or (2), the expanded this far followed by the rest of the pathname is returned quietly. 4. If all of the absolute path was expanded successfully the expanded absolute path is returned.

Value

Returns a character string.

On speed

Internal file.exists() is call while expanding the pathname. This is used to check if there exists a Windows shortcut file named 'foo.lnk' in 'path/foo/bar'. If it does, 'foo.lnk' has to be followed, and in other cases 'foo' is ordinary directory. The file.exists() is unfortunately a bit slow, which is why this function appears slow if called many times.

Author(s)

Henrik Bengtsson

Examples

# Default
print(file.path("foo", "bar", "..", "name")) # "foo/bar/../name"

# Shorten pathname, if possible
print(filePath("foo", "bar", "..", "name"))  # "foo/name"
print(filePath("foo/bar/../name"))           # "foo/name"

# Recognize Windows Shortcut files along the path, cf. Unix soft links
filename <- system.file("data-ex/HISTORY.LNK", package="R.utils")
print(filename)
filename <- filePath(filename, expandLinks="relative")
print(filename)

R.utils

Various Programming Utilities

v2.10.1

LGPL (>= 2.1)

Authors

Henrik Bengtsson [aut, cre, cph]

Initial release