focal (9) vn_fullpath.9freebsd.gz

NAME

     vn_fullpath — convert a vnode reference to a full pathname, given a process context

SYNOPSIS

     #include <sys/param.h>
     #include <sys/vnode.h>

     int
     vn_fullpath(struct thread *td, struct vnode *vp, char **retbuf, char **freebuf);

DESCRIPTION

     The vn_fullpath() function makes a “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 vn_fullpath() function is implemented by inspecting the VFS name cache, and
     attempting to reconstruct a path from the process root to the object.

     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.

     Its arguments are:

     td       The thread performing the call; this pointer will be dereferenced to find the process and its file
              descriptor structure, in order to identify the root vnode to use.

     vp       The vnode to search for.  No need to be locked by the caller.

     retbuf   Pointer to a char * that vn_fullpath() may (on success) point at a newly allocated buffer
              containing the resulting pathname.

     freebuf  Pointer to a char * that vn_fullpath() may (on success) point at a buffer to be freed, when the
              caller is done with retbuf.

     Typical consumers will declare two character pointers: fullpath and freepath; they will set freepath to
     NULL, and fullpath to a name to use in the event that the call to vn_fullpath() fails.  After done with the
     value of fullpath, the caller will check if freepath is non-NULL, and if so, invoke free(9) with a pool
     type of M_TEMP.

RETURN VALUES

     If the vnode is successfully converted to a pathname, 0 is returned; otherwise, an error number is
     returned.

SEE ALSO

     free(9)

AUTHORS

     This manual page was written by Robert Watson <rwatson@FreeBSD.org>.