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extattr(9) [netbsd man page]

EXTATTR(9)						   BSD Kernel Developer's Manual						EXTATTR(9)

extattr -- file system extended attributes SYNOPSIS
#include <sys/param.h> #include <sys/vnode.h> #include <sys/extattr.h> DESCRIPTION
Extended attributes allow additional meta-data to be associated with vnodes representing files and directories. The semantics of this addi- tional data is that of a ``name=value'' pair, where a name may be defined or undefined, and if defined, associated with zero or more bytes of arbitrary binary data. Extended attribute names exist within a set of namespaces; each operation on an extended attribute is required to provide the namespace to which the operation refers. If the same name is present in multiple namespaces, the extended attributes associated with the names are stored and manipulated independently. The following two namespaces are defined universally, although individual file sys- tems may implement additional namespaces, or not implement these namespaces: EXTATTR_NAMESPACE_USER, EXTATTR_NAMESPACE_SYSTEM. The semantics of these attributes are intended to be as follows: user attribute data is protected according the normal discretionary and mandatory protec- tions associated with the data in the file or directory; system attribute data is protected such that appropriate privilege is required to directly access or manipulate these attributes. Reads of extended attribute data may return specific contiguous regions of the meta-data, in the style of VOP_READ(9), but writes will replace the entire current ``value'' associated with a given name. As there are a plethora of file systems with differing extended attributes, availability and functionality of these functions may be limited, and they should be used with awareness of the underlying seman- tics of the supporting file system. Authorization schemes for extended attribute data may also vary by file system, as well as maximum attribute size, and whether or not any or specific new attributes may be defined. Extended attributes are named using a nul-terminated character string. Depending on underlying file system semantics, this name may or may not be case-sensitive. Appropriate vnode extended attribute calls are: VOP_GETEXTATTR(9), VOP_LISTEXTATTR(9), and VOP_SETEXTATTR(9). SEE ALSO
vfsops(9), vnodeops(9) BSD
January 2, 2005 BSD

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VOP_LISTEXTATTR(9)					   BSD Kernel Developer's Manual					VOP_LISTEXTATTR(9)

VOP_LISTEXTATTR -- retrieve a list of named extended attribute from a vnode SYNOPSIS
#include <sys/param.h> #include <sys/vnode.h> #include <sys/extattr.h> int VOP_LISTEXTATTR(struct vnode *vp, int attrnamespace, struct uio *uio, size_t *size, struct ucred *cred, struct thread *td); DESCRIPTION
This vnode call may be used to retrieve a list of named extended attributes from a specified namespace on a file or directory. Its arguments are: vp The vnode of the file or directory. attrnamespace Integer constant indicating which extended attribute namespace the attribute name is present in. uio The location of the data to be read. The resulting data will be a list of attribute names. Each list entry consists of a single byte containing the length of the attribute name, followed by the attribute name. The attribute name is not terminated by ASCII NUL. size If not NULL, on return it will contain the number of bytes required to read the list. In most cases uio will be NULL when size is not, and vice versa. cred The user credentials to use in authorizing the request. td The thread requesting the extended attribute. The cred pointer may be NULL to indicate that access control checks are not to be performed, if possible. This cred setting might be used to allow the kernel to authorize extended attribute retrieval that the active process might not be permitted to do. Extended attribute semantics may vary by file system implementing the call. More information on extended attributes may be found in extattr(9). LOCKS
The vnode will be locked on entry and should remain locked on return. RETURN VALUES
On success, zero will be returned, and the uio structure will be updated to reflect the list read. Otherwise, an appropriate error code is returned. ERRORS
[EACCES] The caller does not have the appropriate privilege. [ENXIO] The request was not valid in this file system for the specified vnode and attribute name. [ENOMEM] Sufficient memory is not available to fulfill the request. [EFAULT] The uio structure refers to an invalid userspace address. [EINVAL] The namespace or uio argument is invalid. [EOPNOTSUPP] The file system does not support VOP_LISTEXTATTR(). SEE ALSO
extattr(9), vnode(9), VOP_GETEXTATTR(9), VOP_SETEXTATTR(9) BSD
August 19, 2005 BSD
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