Mainframe Utility: $RELGEN

/* REXX ***************************************************************/
/* Utility: $RELGEN                                                   */
/* Author: David Leigh                                                */
/* Function: Using GDGGEN (in reverse) return the relative GDG gen    */
/*           of a dataset when it's passed the full dataset name      */
/*           with the G0000V00 as the last node.                      */
/**********************************************************************/
parse upper arg INDSN

/**********************************************************************/
/* get the g0000v00 and the base that was passed in                   */
/**********************************************************************/
indsn = strip(indsn,b,"'")
gv = substr(INDSN,length(INDSN)-7)
xcmd = parse var 'indsn' 'indsn' "'."gv"'" .
interpret xcmd


/**********************************************************************/
/* call gdggen to get the "minus" information                         */
/**********************************************************************/
address tso '%gdggen dsn('indsn')'
address ispexec
'vget gen shared'

/**********************************************************************/
/* loop through the results until you find the one you're looking for */
/**********************************************************************/
if gen > 0 then
  do i = 0 to gen - 1
    'vget minus'i 'shared'
     xcmd = 'xv = substr(minus'i',length(minus'i')-7)'
     interpret xcmd
     if xv = gv then do
       if i = 0 then zdlmsg = i
       else zdlmsg = '-'i
       leave
     end
  end

/**********************************************************************/
/* put the results in the dslist short message variable.              */
/**********************************************************************/
address ispexec 'vput zdlmsg'

EXIT
            

 $RELGEN and its alias $RG take an argument of a GDG dataset including
 the g0000v00 number at the end.  It then calls GDGGEN to determine what
 are all the existing generations.  It returns the relative GDG
 generation number by vputting it into the ZDLMSG pool variable.  If
 called from a 3.4 list screen, this will place the value in the short
 message area.  Alternatively one could call $RELGEN from another
 process and retrieve the value (vget ZDLMSG) and do with it whatever
 they needed.