1.\"- 2.\" Copyright (c) 1999, 2000, 2001, 2003 Robert N. M. Watson 3.\" All rights reserved. 4.\" 5.\" Redistribution and use in source and binary forms, with or without 6.\" modification, are permitted provided that the following conditions 7.\" are met: 8.\" 1. Redistributions of source code must retain the above copyright 9.\" notice, this list of conditions and the following disclaimer. 10.\" 2. Redistributions in binary form must reproduce the above copyright 11.\" notice, this list of conditions and the following disclaimer in the 12.\" documentation and/or other materials provided with the distribution. 13.\" 14.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 15.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 16.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 17.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 18.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 19.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 20.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 21.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 22.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 23.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 24.\" SUCH DAMAGE. 25.\" 26.Dd December 23, 1999 27.Dt VOP_GETEXTATTR 9 28.Os 29.Sh NAME 30.Nm VOP_GETEXTATTR 31.Nd retrieve named extended attribute from a vnode 32.Sh SYNOPSIS 33.In sys/param.h 34.In sys/vnode.h 35.In sys/extattr.h 36.Ft int 37.Fo VOP_GETEXTATTR 38.Fa "struct vnode *vp" 39.Fa "int attrnamespace" 40.Fa "const char *name" 41.Fa "struct uio *uio" 42.Fa "size_t *size" 43.Fa "struct ucred *cred" 44.Fa "struct thread *td" 45.Fc 46.Sh DESCRIPTION 47This vnode call may be used to retrieve a specific named extended attribute 48from a file or directory. 49.Pp 50Its arguments are: 51.Bl -tag -width ".Fa attrnamespace" 52.It Fa vp 53The vnode of the file or directory. 54.It Fa attrnamespace 55Integer constant indicating which extended attribute namespace the attribute 56name is present in. 57.It Fa name 58Pointer to a null-terminated character string containing the attribute name. 59.It Fa uio 60The location of the data to be read. 61.It Fa size 62If not 63.Dv NULL , 64on return it will contain the number of bytes required to read all of the 65attribute data. 66In most cases 67.Fa uio 68will be 69.Dv NULL 70when 71.Fa size 72is not, and vice versa. 73.It Fa cred 74The user credentials to use in authorizing the request. 75.It Fa td 76The thread requesting the extended attribute. 77.El 78.Pp 79The 80.Fa cred 81pointer may be 82.Dv NULL 83to indicate that access control checks are not to be performed, if possible. 84This 85.Fa cred 86setting might be used to allow the kernel to authorize extended attribute 87retrieval that the active process might not be permitted to do. 88.Pp 89Extended attribute semantics may vary by file system implementing the call. 90More information on extended attributes may be found in 91.Xr extattr 9 . 92.Sh LOCKS 93The vnode will be locked on entry and should remain locked on return. 94.Sh RETURN VALUES 95On success, zero will be returned, and the uio structure will be updated to 96reflect data read. 97Otherwise, an appropriate error code is returned. 98.Sh ERRORS 99.Bl -tag -width Er 100.It Bq Er ENOATTR 101The requested attribute was not defined for this vnode. 102.It Bq Er EACCES 103The caller does not have the appropriate privilege. 104.It Bq Er ENXIO 105The request was not valid in this file system for the specified vnode and 106attribute name. 107.It Bq Er ENOMEM 108Sufficient memory is not available to fulfill the request. 109.It Bq Er EFAULT 110The uio structure refers to an invalid userspace address. 111.It Bq Er EINVAL 112The 113.Fa name , 114.Fa namespace , 115or 116.Fa uio 117argument is invalid. 118.It Bq Er EOPNOTSUPP 119The file system does not support 120.Fn VOP_GETEXTATTR . 121.El 122.Sh SEE ALSO 123.Xr extattr 9 , 124.Xr vnode 9 , 125.Xr VOP_LISTEXTATTR 9 , 126.Xr VOP_SETEXTATTR 9 127.Sh BUGS 128By passing in the empty string as the attribute name, some file systems 129will return a list of defined names on the target vnode for the 130requested namespace. 131This is a bad API, and will be replaced by an explicit VOP. 132