/sys$common/syshlp/helplib.hlb CC, Run-time functions, umask  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  Creates a file protection mask that is used when a new file is
  created and returns the previous mask value.

  Syntax:

       #include <stat.h>

       mode_t umask(mode_t mode_complement);