Return_Values

   0                  Indicates success.
   x                  Indicates that the function specified by
                      the function argument stops its search, and
                      returns the value that was returned by the
                      function.
   -1                 Indicates an error; errno is set to one of the
                      following values:

                      o  EACCES - Search permission is denied for
                         any component of the path argument or read
                         permission is denied for the path argument.

                      o  ENAMETOOLONG - The length of the path
                         string exceeds PATH_MAX, or a pathname
                         component is longer than NAME_MAX while
                         [_POSIX_NO_TRUNC] is in effect.

                      o  ENOENT - The path argument points to the
                         name of a file that does not exist or
                         points to an empty string.

                      o  ENOMEM - There is insufficient memory for
                         this operation.

                      Also, if the function pointed to by the
                      function argument encounters an error, errno
                      can be set accordingly.