.\" -*- nroff -*-
.\"
.\" Copyright (c) 1996 Doug Rabson
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $FreeBSD$
.\"
.Dd August 29, 2008
.Os
.Dt VOP_ATTRIB 9
.Sh NAME
.Nm VOP_GETATTR ,
.Nm VOP_SETATTR
.Nd get and set attributes on a file or directory
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fn VOP_GETATTR "struct vnode *vp" "struct vattr *vap" "struct ucred *cred"
.Ft int
.Fn VOP_SETATTR "struct vnode *vp" "struct vattr *vap" "struct ucred *cred"
.Sh DESCRIPTION
These entry points manipulate various attributes of a file or directory,
including file permissions, owner, group, size,
access time and modification time.
.Pp
The arguments are:
.Bl -tag -width cred
.It Fa vp
The vnode of the file.
.It Fa vap
The attributes of the file.
.It Fa cred
The user credentials of the calling process.
.El
.Pp
Attributes which are not being modified by
.Fn VOP_SETATTR
should be set to the value
.Dv VNOVAL ;
.Fn VATTR_NULL
may be used to clear all the values, and should generally be used to reset
the contents of
.Fa *vap
prior to setting specific values.
.Sh LOCKS
.Fn VOP_GETATTR
expects the vnode to be locked on entry and will leave the vnode locked on
return.
The lock type can be either shared or exclusive.
.Pp
.Fn VOP_SETATTR
expects the vnode to be locked on entry and will leave the vnode locked on
return.
The lock type must be exclusive.
.Sh RETURN VALUES
.Fn VOP_GETATTR
returns 0 if it was able to retrieve the attribute data via
.Fa *vap ,
otherwise an appropriate error is returned.
.Fn VOP_SETATTR
returns zero if the attributes were changed successfully, otherwise an
appropriate error is returned.
.Sh PSEUDOCODE
.Bd -literal
int
vop_getattr(struct vnode *vp, struct vattr *vap, struct ucred *cred)
{

    /*
     * Fill in the contents of *vap with information from
     * the file system.
     */
    ...;

    return 0;
}

int
vop_setattr(struct vnode *vp, struct vattr *vap, struct ucred *cred)
{

    /*
     * Check for unsettable attributes.
     */
    if ((vap->va_type != VNON) || (vap->va_nlink != VNOVAL) ||
	(vap->va_fsid != VNOVAL) || (vap->va_fileid != VNOVAL) ||
	(vap->va_blocksize != VNOVAL) || (vap->va_rdev != VNOVAL) ||
	((int)vap->va_bytes != VNOVAL) || (vap->va_gen != VNOVAL)) {
	return (EINVAL);
    }

    if (vap->va_flags != VNOVAL) {
	/*
	 * Set the immutable and append flags of the file.
	 */
    }

    if (vap->va_uid != (uid_t)VNOVAL || vap->va_gid != (gid_t)VNOVAL) {
	/*
	 * Change owner and/or group of the file.
	 */
    }

    if (vap->va_size != VNOVAL) {
	/*
	 * Truncate the file to the specified size.
	 */
    }

    if (vap->va_atime.tv_sec != VNOVAL || vap->va_mtime.tv_sec != VNOVAL) {
	/*
	 * Change access and/or modification time of file.
	 */
    }

    if (vap->va_mode != (mode_t)VNOVAL) {
	/*
	 * Change permissions of file.
	 */
    }

    return 0;
}
.Ed
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPERM
The file is immutable.
.It Bq Er EACCES
The caller does not have permission to modify the file or directory attributes.
.It Bq Er EROFS
The file system is read-only.
.El
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr vnode 9 ,
.Xr VOP_ACCESS 9
.Sh AUTHORS
This manual page was written by
.An Doug Rabson .