Extended Attributes

Extended attributes (EAs) are a mechanism whereby an application can 
attach information to a file system object (directories or files) 
describing the object to another application, to the operating system, or 
to the FSD managing that object. 

EAs associated with a file object are not part of a file object's data, 
but are maintained separately and managed by the file system that manages 
that object. 

Each extended attribute consists of a name and a value. An EA name 
consists of ASCII text, chosen by the application developer, that is used 
to identify a particular EA. EA names are restricted to the same character 
set as a filename. An EA value consists of arbitrary data, that is, data 
of any form. Because of this OS/2 does not check data that is associated 
with an EA. 

So that EA data is understandable to other applications, conventions have 
been established for: 

oNaming EAs 
oIndicating the type of data contained in EAs 
  

In addition, a set of standard EAs (SEAs) have been defined. SEAs define a 
common set of information that can be associated with most files (for 
example, file type and file purpose). Through SEAs, many applications can 
access the same , useful information associated with files. 

Applications are not limited to using SEAs to associate information with 
files. They may define their own application-specific extended attributes. 
Applications define and associate extended attributes with a file object 
through file system function calls. 

See the OS/2 Version 2.0 Programming Guide for a complete description of 
EA naming conventions and data types and standard extended attributes. See 
also the OS/2 Version 2.0 Control Program Programming Reference for a 
complete description of the file system function calls. 

EAs may be viewed as a property list attached to file objects. The 
services for manipulating EAs are: add/replace a series of name/value 
pairs, return name/value pairs given a list of names, and return the total 
set of EAs. 

There are two formats for EAs as passed to OS/2 Version 2.0 API: Full EAs 
(FEA) and Get EAs (GEA).