Use Monitor to Trap QCMDEXC Errors

August 23, 2002 Timothy Prickett Morgan

Hey, Ted:

How do I find out why QCMDEXC failed when called in an RPG program?

— John

Trap the error so your program doesn’t cancel. I like the new monitor and on-error op codes for this:

D QCmdExc         pr                  extpgm('QCMDEXC') 
D    Cmd                       256a   const             
D    CmdLen                     15p 5 const             
                                                        
D Cmd             s            256                      
                                                        
D psds           sds                                    
D   MsgID                40     46                      
D   Msg                  91    170                      
                                                        
C                   eval      cmd = 'dsplib br549'      
C                   monitor                             
C                   callp     qcmdexc (cmd: %size(cmd)) 
C                   on-error                            
C* call to qcmdexc failed -- do whatever 
C                   endmon                              

If you prefer, you can add an argument of *program in factor 2 of the on-error command, but it’s not necessary:

C                   on-error  *program                  

If an error occurs, check positions 40 through 46 of the program status data structure for the message ID. Look in positions 91 through 170 for the error message text.

The monitor and on-error op codes are similar in concept to the CL Monitor Message (MONMSG) command or the Java try/catch operations. I like monitor and on-error better than the following older methods.

If you’re not on V5, you can use the ‘old’ way to trap the failed call: the e operation extender, followed by a test for the %error function:

C                   callp (e) qcmdexc (cmd: %size(cmd)) 
C                   if        %error                    
C* do whatever
C                   endif                               

Of course, there’s the ‘old old’ method: an indicator in the ‘lo’ resulting indicator position, but I won’t recommend it.

— Ted

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