Description

   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.