134 lines
4.1 KiB
Groff
134 lines
4.1 KiB
Groff
.\"-
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.\" Copyright (c) 1999, 2000, 2001, 2003 Robert N. M. Watson
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd December 23, 1999
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.Os
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.Dt VOP_GETEXTATTR 9
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.Sh NAME
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.Nm VOP_GETEXTATTR
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.Nd retrieve named extended attribute from a vnode
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/vnode.h
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.In sys/extattr.h
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.Ft int
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.Fo VOP_GETEXTATTR
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.Fa "struct vnode *vp"
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.Fa "int attrnamespace"
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.Fa "const char *name"
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.Fa "struct uio *uio"
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.Fa "size_t *size"
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.Fa "struct ucred *cred"
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.Fa "struct thread *td"
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.Fc
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.Sh DESCRIPTION
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This vnode call may be used to retrieve a specific named extended attribute
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from a file or directory.
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.Pp
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Its arguments are:
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.Bl -tag -width ".Fa attrnamespace"
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.It Fa vp
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the vnode of the file or directory
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.It Fa attrnamespace
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integer constant indicating which extended attribute namespace the attribute
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name is present in
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.It Fa name
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pointer to a null-terminated character string containing the attribute name
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.It Fa uio
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the location of the data to be read
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.It Fa size
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if not
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.Dv NULL ,
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on return it will contain the number of bytes required to read all of the
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attribute data.
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In most cases
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.Fa uio
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will be
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.Dv NULL
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when
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.Fa size
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is not, and vise versa.
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.It Fa cred
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the user credentials to use in authorizing the request
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.It Fa td
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the thread requesting the extended attribute
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.El
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.Pp
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The
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.Fa cred
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pointer may be
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.Dv NULL
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to indicate that access control checks are not to be performed, if possible.
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This
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.Fa cred
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setting might be used to allow the kernel to authorize extended attribute
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retrieval that the active process might not be permitted to do.
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.Pp
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Extended attribute semantics may vary by file system implementing the call.
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More information on extended attributes may be found in
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.Xr extattr 9 .
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.Sh LOCKS
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The vnode will be locked on entry and should remain locked on return.
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.Sh RETURN VALUES
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On success, zero will be returned, and the uio structure will be updated to
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reflect data read.
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Otherwise, an appropriate error code is returned.
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.Sh ERRORS
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.Bl -tag -width Er
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.It Bq Er ENOATTR
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The requested attribute was not defined for this vnode.
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.It Bq Er EACCES
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The the caller does not have the appropriate privilege.
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.It Bq Er ENXIO
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The request was not valid in this file system for the specified vnode and
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attribute name.
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.It Bq Er ENOMEM
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Sufficient memory is not available to fulfill the request.
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.It Bq Er EFAULT
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The uio structure refers to an invalid userspace address.
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.It Bq Er EINVAL
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The
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.Fa name ,
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.Fa namespace,
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or
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.Fa uio
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argument is invalid.
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.It Bq Er EOPNOTSUPP
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The file system does not support
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.Fn VOP_GETEXTATTR .
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.El
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.Sh SEE ALSO
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.Xr extattr 9 ,
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.Xr vnode 9 ,
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.Xr VOP_LISTEXTATTR 9 ,
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.Xr VOP_SETEXTATTR 9
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.Sh BUGS
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By passing in the empty string as the attribute name, some file systems
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will return a list of defined names on the target vnode for the
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requested namespace.
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This is a bad API, and will be replaced by an explicit VOP.
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