16EXTENDED ATTRIBUTES

This chapter describes extended attributes (EAs), which allow arbitrary metadata, in the form of name-value pairs, to be associated with file i-nodes. EAs were added to Linux in version 2.6.

16.1 Overview

EAs are used to implement access control lists (Chapter 17) and file capabilities (Chapter 39). However, the design of EAs is general enough to allow them to be used for other purposes as well. For example, EAs could be used to record a file version number, information about the MIME type or character set for the file, or (a pointer to) a graphical icon.

EAs are not specified in SUSv3. However, a similar feature is provided on a few other UNIX implementations, notably the modern BSDs (see extattr(2)) and Solaris 9 and later ...

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