KCAPSHR is a callable entry point in a protected shared image which
   allows you to call KeyCapture as a subroutine, from your own programs
   and menus. Note that KCAP_Vx.EXE calls this KCAPSHR passing it the
   command line which was entered as a DCL foreign command.

      Format:

        CALLS #5,G^KCAPSHR kcapcmd ,actrtn ,facnam ,actprm ,outlen

      Arguments:

   kcapcmd

   VMS usage: char_string
   type: character string
   access: read only
   mechanism: by descriptor--fixed length string descriptor

   Character string containing the KeyCapture command to be executed. The
   kcapcmd argument is the address of a descriptor specifying the command
   string being passed to KCAPSHR. It must begin with the verb KCAP. The
   syntax rules for this command string are the same as for any command
   which KeyCapture would process from the DCL command prompt.

   kcapcmd may not be passed as zero but the length in the descriptor of
   the command may be 0 which will cause KCAPSHR to prompt for a command
   interactively.

   actrtn

   CALLING OF THE USER'S ACTRTN IS NOT YET IMPLEMENTED FOR VERSION 4
   on AXP.

   VMS usage: procedure
   type: procedure entry mask
   access: call without stack unwinding
   mechanism: by reference

   User-supplied action routine to be executed during message
   processing. The actrtn argument is the address of the entry mask of
   this routine. If an actrtn is specified and the actrtn returns a
   success status (the low bit of R0 is set) then the message is output
   using $PUTMSG. If the actrtn returns a failure status, (the low bit
   of R0 clear) then no message is output. If specified as 0 then no
   actrtn is called and the messages are output by $PUTMSG.

   facnam

   VMS usage: char_string
   type: character-coded text string
   access: read only
   mechanism: by descriptor--fixed length string descriptor

   Facility prefix to be used in the first or only message written by
   $PUTMSG. The facnam argument is the address of a character string
   descriptor pointing to this facility prefix. If passed as 0 then
   KCAP is used as the facility name.

   actprm

   CALLING OF THE USER'S ACTRTN IS NOT YET IMPLEMENTED FOR VERSION 4
   on AXP.

   VMS usage: user_arg
   type: longword (unsigned)
   access: read only
   mechanism: by value

   Parameter to be passed to the action routine. The actprm is a
   longword value containing this parameter. If there is no
   parameter to pass then actprm should be specified as 0.

   outlen

   VMS usage: word_unsigned
   type: word (unsigned)
   access: write only
   mechanism: by reference

   The number of bytes in the command passed to KCAPSHR is
   returned here unless the command passed was only "KCAP/COMMAND"
   in which case outlen is returned as zero indicating
   that there was no actual command passed and that a command was
   prompted for interactively and executed.  This is useful for
   determining whether or not to call KCAPSHR again in prompting mode.

   This argument must be passed as the address of a word in the calling
   program for which there is write access.