74 lines
2.7 KiB
Markdown
74 lines
2.7 KiB
Markdown
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# xattr
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## Interface for extended filesystem attributes
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[Extended attributes](https://en.wikipedia.org/wiki/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.
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This is a simple interface for accessing them within [Chicken Scheme](https://call-cc.org/), a friendly Scheme.
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## API
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### get-xattr
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`get-xattr path attr`
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Returns the string-value of a file's extended attribute.
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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.
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### set-xattr
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`set-xattr path attr value`
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Sets the string-value of a file's extended attribute.
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The set value is returned, if successful.
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### remove-xattr
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`remove-xattr path attr`
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Removes an extended attribute from a file.
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The value of the removed attribute is returned, if successful.
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### list-xattrs
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`list-xattrs path`
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Returns a list of the file's extended attribute names.
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## Examples
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```
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(import xattr (chicken io) (chicken file))
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;; Create the test file
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(call-with-output-file "testing.txt"
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(lambda (out-port) (write-line "Just a test!" out-port)))
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(set-xattr "testing.txt" "user.dublincore.author" "Migdal E. F. Lemmings")
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(set-xattr "testing.txt" "user.dublincore.title" "A Treatise on Almonds")
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(get-xattr "testing.txt" "user.dublincore.author")
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;; Returns "Migdal E. F. Lemmings"
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(list-xattrs "testing.txt")
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;; Returns '("user.dublincore.author" "user.dublincore.title")
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(remove-xattr "testing.txt" "user.dublincore.title")
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;; Returns "A Treatise on Almonds"
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(list-xattrs "testing.txt")
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;; Now returns '("user.dublincore.author")
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```
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## On GNU/Linux
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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.
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Don't forget to prepend “user.” to your attribute names!
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A handy list of somewhat-standard extended attributes is hosted on FreeDesktop's website, [here](https://www.freedesktop.org/wiki/CommonExtendedAttributes/).
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## Requirements
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This egg requires `srfi-1` and `srfi-12`.
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## Meta
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**Author:** Jaidyn Ann <jadedctrl@posteo.at>
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**License:** GPLv3
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**Source:** https://github.com/jadedctrl/xattr, https://notabug.org/jadedctrl/xattr
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