Extended file attributes: Difference between revisions

Revision as of 16:56, 14 June 2020

Revision as of 16:57, 14 June 2020

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[[Mac OS X Tiger|Mac OS X 10.4]] and later support extended attributes by making use of the [[HFS Plus|HFS+]] filesystem Attributes file [[B*-tree]] feature which allows for named forks. Although the named forks in HFS+ support arbitrarily large amounts of data through extents, the OS support for extended attributes only supports inline attributes, limiting their size to that which can fit within a single B*-tree node.{{citation needed|date=September 2012}} Any regular file may have a list of extended attributes. HFS+ supports an arbitrary number of named forks, and it is unknown if [[macOS]] imposes any limit on the number of extended attributes. Each attribute consists of a name and the associated data. The name is a [[null-terminated string|null-terminated]] [[Unicode]] string.

The macOS APIs supportsupports listing,<ref>{{man|2|listxattr|Darwin}}</ref> getting,<ref>{{man|2|getxattr|Darwin}}</ref> setting,<ref>{{man|2|setxattr|Darwin}}</ref> and removing<ref>{{man|2|removexattr|Darwin}}</ref> extended attributes from files or directories using a Linux-like API. From the command line, these abilities are exposed through the ''xattr'' utility.<ref>{{man|1|xattr|Darwin}}</ref>

Since macOS 10.5, files originating from the web are marked with <code>com.apple.quarantine</code> via extended file attributes.<ref>{{cite web |title=Launch Services Release Notes |url=https://developer.apple.com/library/archive/releasenotes/Carbon/RN-LaunchServices/index.html |website=developer.apple.com}}</ref> In some older versions of macOS (such as [[Mac OS X Snow Leopard|Mac OS X 10.6]]), user space extended attributes were not preserved on save in common [[Cocoa (API)|Cocoa]] applications (TextEdit, Preview etc.).{{citation needed|date=October 2012}}