VMS Help CC, Language topics, Builtin Functions, Span Characters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  The _SPANC function locates the first character in a string without
  certain attributes.  The attributes are specified through a table
  and a mask.

  Syntax:

       unsigned short _SPANC(unsigned short __length, const char
                             *__string, const char *__table, char
                             __mask, ...);

  where the optional argument (...) is char **mask.