With DECC$POSIX_COMPLIANT_PATHNAMES enabled, an application
    is allowed to present POSIX-compliant pathnames to any C RTL
    function that accepts a pathname.

    By default DECC$POSIX_COMPLIANT_PATHNAMES is disabled, and the
    usual C RTL behavior prevails. This disabled mode includes
    interpretation of pathnames as UNIX style specifications and
    uses rules that are different and unrelated to POSIX-compliant
    pathname processing.

    To enable DECC$POSIX_COMPLIANT_PATHNAMES, set it to one of the
    following values:

      1 All pathnames are designated as POSIX style.
      2 Pathnames that end in ":" or contain any of the bracket
        characters "[]<>", and that can be successfully parsed by
        the SYS$FILESCAN service, are designated as OpenVMS style.
        Otherwise, they are designated as POSIX style.
      3 The pathnames "." and "..", or pathnames that contain "/" are
        designated as POSIX style. Otherwise, they are designated as
        OpenVMS style.
      4 All pathnames are designated as OpenVMS style.

    See Chapter 12 of the VSI C Run-Time Library Reference Manual
    for OpenVMS Systems for more information on POSIX-compliant
    pathnames and symbolic links.