.\"
.\" Copyright (c) 2003 Robert N. M. Watson.
.\" All rights reserved.
.\"
.\" 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(s), this list of conditions and the following disclaimer as
.\"    the first lines of this file unmodified other than the possible
.\"    addition of one or more copyright notices.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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.
.\"
.Dd June 15, 2021
.Dt VN_FULLPATH 9
.Os
.Sh NAME
.Nm vn_fullpath
.Nd "convert a vnode reference to a full pathname, given a process context"
.Sh SYNOPSIS
.In sys/param.h
.In sys/vnode.h
.Ft int
.Fo vn_fullpath
.Fa "struct vnode *vp" "char **retbuf" "char **freebuf"
.Fc
.Sh DESCRIPTION
The
.Fn vn_fullpath
function makes a
.Dq "best effort"
attempt to generate a string pathname for
the passed vnode; the resulting path, if any, will be relative to
the root directory of the process associated with the passed thread pointer.
The
.Fn vn_fullpath
function
is implemented by inspecting the VFS name cache, and attempting to
reconstruct a path from the process root to the object.
.Pp
This process is necessarily unreliable for several reasons: intermediate
entries in the path may not be found in the cache; files may have more
than one name (hard links), not all file systems use the name cache
(specifically, most synthetic file systems do not); a single name may
be used for more than one file (in the context of file systems covering
other file systems); a file may have no name (if deleted but still
open or referenced).
However, the resulting string may still be more useable to a user than
a vnode pointer value, or a device number and inode number.
Code consuming the results of this function should anticipate (and
properly handle) failure.
.Pp
Its arguments are:
.Bl -tag -width ".Fa freebuf"
.It Fa vp
The vnode to search for.
No need to be locked by the caller.
.It Fa retbuf
Pointer to a
.Vt "char *"
that
.Fn vn_fullpath
may (on success) point at a newly
allocated buffer containing the resulting pathname.
.It Fa freebuf
Pointer to a
.Vt "char *"
that
.Fn vn_fullpath
may (on success) point at a buffer
to be freed, when the caller is done with
.Fa retbuf .
.El
.Pp
Typical consumers will declare two character pointers:
.Va fullpath
and
.Va freepath ;
they will set
.Va freepath
to
.Dv NULL ,
and
.Va fullpath
to a name to use
in the event that the call to
.Fn vn_fullpath
fails.
After done with the value of
.Va fullpath ,
the caller will check if
.Va freepath
is
.Pf non- Dv NULL ,
and if so, invoke
.Xr free 9
with a pool type of
.Dv M_TEMP .
.Sh RETURN VALUES
If the vnode is successfully converted to a pathname, 0 is returned;
otherwise, an error number is returned.
.Sh SEE ALSO
.Xr free 9
.Sh AUTHORS
This manual page was written by
.An Robert Watson Aq Mt rwatson@FreeBSD.org .