Re: AW: Additional Error Specs from C-Proc. 'system' -- RPG400-L

If you go to google.com and search for qcapcmd, you'll
find a link to the source code of a working example of
qcapcmd.

phil

> Simon,
>
> I agree with your arguments. I never used QCAPCMD before and had now a look
> to IBM's API docu. One question to your example snippet: You specified for
> optCtlBlk a LIKE(Qca_PCMD_CPOP0100). What is this reference data structure?
> Is it standard or your own built? Where is it located? I didn't find it in
> other command descriptions.
> Regards,
> Werner Noll
>
> -----Urspr�ngliche Nachricht-----
> Von: Simon Coulter [mailto:shc@flybynight.com.au]
> Gesendet: Dienstag, 6. August 2002 01:31
> An: rpg400-l@midrange.com
> Betreff: Re: Additional Error Specs from C-Proc. 'system'
>
>
>
> Hello Nelson,
>
> You wrote:
> >I've probably missed this in previous threads, but what is the value or
> >benefit of using the C 'system' over using QCAPCMD in the first place?
>
> Because it is simple and it allows literal strings to be used in an easier
> manner.  For example, the following definitions:
>
> D int_t           S             10I 0
> D pointer_t       S               *
> D rc              S                   LIKE(int_t)
>
> D system          PR                  LIKE(int_t) EXTPROC('system')
>  *
>  * Required parameter group:
>  *                             OS/400 command
> D   command                           LIKE(pointer_t) VALUE
> D                                     OPTIONS(*STRING)
>
> allow me to code:
>
> C             callp           system("DSPMSG")
>
> or
>
> C             eval            rc = system("DSPMSG")
>
> whereas using QCMDEXC with the following prototype:
>
>  /if defined(LONG_PROC_NAMES)
> D QcaRunClCmd     PR
>  /else
> D QCMDEXC         PR
>  /endif
> D                                     EXTPGM('QCMDEXC')
>  *
>  * Required parameter group:
>  *                              A Control Language command string
> D  clCmd                     32702    CONST OPTIONS(*VARSIZE)
>  *                              Length of command string
> D  clCmdLen                     15  5 CONST
>  *
>  * Optional parameter group:
>  *                              A DBCS data flag
> D  dbcsFlag                      3    CONST OPTIONS(*NOPASS)
>
> requires:
>
> C             callp           QCMDEXC("DSPMSG" : 6)
>
> or
>
> D $CMD                C                       CONST('DSPMSG')
>
> C             callp           QCMDEXC($CMD : %SIZE($CMD))
>
> both of which are slightly uglier than system().
>
> Using QCAPCMD is uglier still but much more powerful since its prototype
> looks like:
>
>  /if defined(LONG_PROC_NAMES)
> D QcaProcessClCmd...
> D                 PR
>  /else
> D QCAPCMD         PR
>  /endif
> D                                     EXTPGM('QCAPCMD')
>  *
>  * Required parameter group:
>  *                              Command string to process
> D  clCmd                     32702    CONST OPTIONS(*VARSIZE)
>  *                              Length of command string
> D  cmdLen                       10I 0 CONST
>  *                              Options control block
> D  optCtlBlk                          LIKE(Qca_PCMD_CPOP0100)
> D                                     CONST OPTIONS(*VARSIZE)
>  *                              Length of options control block
> D  optCtlBlkLen                 10I 0 CONST
>  *                              Format of options control block
> D  format                        8    CONST
>  *                              Changed command string
> D  chgClCmd                  32767    OPTIONS(*VARSIZE:*OMIT)
>  *                              Length provided for changed command string
> D  chgClCmdLenProv...
> D                               10I 0 CONST
>  *                              Length available for changed command
> string
> D  chgClCmdLenAvail...
> D                               10I 0
>  *                              Error code
> D  errorCode                  1024    OPTIONS(*VARSIZE)
>
> In all the "ugly" cases the solution is to create a wrapper procedure that
> masks the ugliness behind a nice interface.  For example:
>
> C             eval            errCode = runCLcmd("DSPMSG")
>
> where runCLcmd is a nice wrapper procedure that may in turn use either
> QCMDEXC or QCAPCMD or even system.
>
> I use system where I expect the command to succeed (e.g., DSPMSG is
> unlikely to fail) but I use the other methods when there is a reasonable
> chance of the command failing.  However, if you take the effort to create
> a decent runCLcmd procedure you get the best of both worlds.
>
> Regards,
> Simon Coulter.
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>
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