#include <db.h> int DB->fd(DB *db, int *fdp);
         The DB->fd() method provides access to a file descriptor
         representative of the underlying database.  A file descriptor
         referring to the same file will be returned to all processes that call
         DB->open()  with the same
         file parameter.
    
This file descriptor may be safely used as a parameter to the fcntl(2) and flock(2) locking functions.
         The DB->fd() method only supports a coarse-grained form of locking.
         Applications should instead use the Berkeley DB lock manager where
         possible.
    
         The DB->fd() 
            
                  method returns a non-zero error value on failure and 0 on success.