- retrieve named extended attribute from a vnode
#include <sys/extattr.h> int
Fa struct vnode *vp
Fa int attrnamespace
Fa const char *name
Fa struct uio *uio
Fa size_t *size
Fa struct ucred *cred
Fa struct thread *td
This vnode call may be used to retrieve a specific named extended attribute
from a file or directory.
Its arguments are:
The vnode of the file or directory.
Integer constant indicating which extended attribute namespace the attribute
name is present in.
Pointer to a null-terminated character string containing the attribute name.
The location of the data to be read.
on return it will contain the number of bytes required to read all of the
In most cases
is not, and vise versa.
The user credentials to use in authorizing the request.
The thread requesting the extended attribute.
pointer may be
to indicate that access control checks are not to be performed, if possible.
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
The vnode will be locked on entry and should remain locked on return.
On success, zero will be returned, and the uio structure will be updated to
reflect data read.
Otherwise, an appropriate error code is returned.
Bq Er ENOATTR
The requested attribute was not defined for this vnode.
Bq Er EACCES
The the caller does not have the appropriate privilege.
Bq Er ENXIO
The request was not valid in this file system for the specified vnode and
Bq Er ENOMEM
Sufficient memory is not available to fulfill the request.
Bq Er EFAULT
The uio structure refers to an invalid userspace address.
Bq Er EINVAL
Fa name ,
argument is invalid.
Bq Er EOPNOTSUPP
The file system does not support
By passing in the empty string as the attribute name, some file systems
will return a list of defined names on the target vnode for the
This is a bad API, and will be replaced by an explicit VOP.