freebsd-dev/share/man/man9/VOP_ATTRIB.9

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.Dd July 24, 1996
.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" "struct thread *td"
.Ft int
.Fn VOP_SETATTR "struct vnode *vp" "struct vattr *vap" "struct ucred *cred" "struct thread *td"
.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
.It Fa td
the thread
.El
.Pp
Attributes which are not being modified by
.Xr VOP_SETATTR 9
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
.Xr VOP_GETATTR 9
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
.Xr VOP_SETATTR 9
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
.Xr VOP_GETATTR 9
returns 0 if it was able to retrieve the attribute data via
.Fa *vap ,
otherwise an appropriate error is returned.
.Xr VOP_SETATTR 9
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, struct thread *td)
{
    /*
     * Fill in the contents of *vap with information from
     * the filesystem.
     */
    ...;

    return 0;
}

int
vop_setattr(struct vnode *vp, struct vattr *vap,
	    struct ucred *cred, struct thread *td)
{
    /*
     * 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 filesystem is read-only.
.El
.Sh SEE ALSO
.Xr VFS 9 ,
.Xr vnode 9 ,
.Xr VOP_ACCESS 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .