xattr

Interface for extended filesystem attributes

Extended attributes are a special type of file attribute that lets you associate key-value pairs with a file without actually modifying the file's contents. Commonly used for program settings, tagging, and file metadata (i.e., storing a file's author with a key like “author.name”) xattrs can be used for used for pretty much anything you can dream up. They're mega-cool and useful.

This is a simple interface for accessing them within Chicken Scheme, a friendly Scheme.

API

get-xattr

get-xattr path attr

Returns the string-value of a file's extended attribute.
If the file has no such attribute, #f is returned. In other cases (e.g., the file doesn't exist, permission not available, no filesystem support), exceptions are raised.

set-xattr

set-xattr path attr value

Sets the string-value of a file's extended attribute.
The set value is returned, if successful.

remove-xattr

remove-xattr path attr

Removes an extended attribute from a file.
The value of the removed attribute is returned, if successful.

list-xattrs

list-xattrs path

Returns a list of the file's extended attribute names.

Examples

(import xattr (chicken io) (chicken file))
;; Create the test file
(call-with-output-file "testing.txt"
                       (lambda (out-port) (write-line "Just a test!" out-port)))

(set-xattr "testing.txt" "user.dublincore.author" "Migdal E. F. Lemmings")
(set-xattr "testing.txt" "user.dublincore.title" "A Treatise on Almonds")

(get-xattr "testing.txt" "user.dublincore.author")
;; Returns "Migdal E. F. Lemmings"

(list-xattrs "testing.txt")
;; Returns '("user.dublincore.author" "user.dublincore.title")

(remove-xattr "testing.txt" "user.dublincore.title")
;; Returns "A Treatise on Almonds"

(list-xattrs "testing.txt")
;; Now returns '("user.dublincore.author")

On GNU/Linux

Currently, this egg only supports LiGNUx, a platform that has a particularity: The name of each attribute must contain a “namespace,” separated from the actual name by a period. For example, with the attribute named user.xdg.origin.url, the namespace is user and the name is xdg.origin.url. In most cases, you won't stray from the user namespace.

Don't forget to prepend “user.” to your attribute names!

A handy list of somewhat-standard extended attributes is hosted on FreeDesktop's website, here.

Requirements

This egg requires srfi-1.

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