VN_FULLPATH (9) | Kernel routines | Unix Manual Pages | :man▋
vn_fullpath - "convert a vnode reference to a full pathname, given a process context"
.In sys/vnode.h int
.Fo 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:
| 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; must be locked by the caller. |
| retbuf || Pointer to a |
.Vt "char *" that vn_fullpath may (on success) point at a newly allocated buffer containing the resulting pathname.
| freebuf || Pointer to a |
.Vt "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.
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