If a version of the file exists, a new file created with open
    inherits certain attributes from the existing file unless
    those attributes are specified in the open call. The following
    attributes are inherited: record format, maximum record size,
    carriage control, and file protection.

                                  NOTES

       o  If you intend to do random writing to a file, the file
          must be opened for update by specifying a flags value of
          O_RDWR.

       o  To create files with OpenVMS RMS default protections
          by using the UNIX system-call functions umask, mkdir,
          creat, and open, call mkdir, creat, and open with a
          file-protection mode argument of 0777 in a program that
          never specifically calls umask. These default protections
          include correctly establishing protections based on ACLs,
          previous versions of files, and so on.

          In programs that do vfork/exec calls, the new process
          image inherits whether umask has ever been called or not
          from the calling process image. The umask setting and
          whether the umask function has ever been called are both
          inherited attributes.

    See also creat, read, write, close, dup, dup2, and lseek.