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.