xref: /freebsd/share/man/man9/vn_fullpath.9 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

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.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 .