In VSI C source programs, you can include both OpenVMS and UNIX*
  style file specifications.  Combinations of the two specifications
  are not supported by VSI C.

  Example of a valid UNIX* file specification:

       beatle!/dba0/lennon/songs.lis.3

  Example of an invalid UNIX* file specification:

       BEATLE::DBA0:[LENNON.C]/songs.lis.3

 ----------
 * UNIX is a trademark of The Open Group.