VN_FULLPATH(9) MidnightBSD Kernel Developer’s Manual VN_FULLPATH(9)


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


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


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


The vn_fullpath() function makes a ‘‘best effort’’ attempt to generate a string pathname for the passed (locked) 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:


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.


The vnode to search for; must be locked by the caller.


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


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.


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




This manual page was written by Robert Watson 〈〉.

MidnightBSD 0.3 January 11, 2004 MidnightBSD 0.3