Re: SYSTEM prototype?

P
Hello John,

You wrote:
>Is there a place where one can "Easily" find what the valid values are for
>the return codes from API's

That depends on your definition of "easily" :)  Most APIs are documented in 
System Programmers API Reference.  The sections of this manual are scattered 
between the Softcopy Library and the Disinformation Centre prior to VRM450.  
At VRM450 all the API documentation is in the DC.  The hard part is knowing 
which section to read.  You need to know whether an 'API' is a system API, a 
Unix-type API, or part of the C run-time library.

APIs like system() are part of the C run-time library and are documented in 
the C Run-time Library Reference in the Softcopy Library.

If you know the API name and can determine which section of the manual 
describes it then you can find a list of associated error codes.

I think that was my first RTFM for the new Millennium -- which started only 
31 days ago ... :)

>And what they mean?    

Yes, see above.

>I would suspect there is a correlation between what
>is returned in the 10i  return code and the 7 byte ErrorCode.  Right?   Can
>one just get alisting by API the valid 10i return codes and a description?

No correlation at all.  (mostly) Only the Unix type APIs do this. The AS/400 
APIs return a standard API error code structure which contains a real AS/400 
message ID.  The Unix APIs generally do one of two things:  

        1/ They return a negative value to indicate failure.  Sometimes a 
range of negative values will be returned indicating different reasons for 
failure.  

        2/ However, it is more common for a Unix API to return -1 to indicate 
failure and put the real reason in the errno variable which seems magically 
available to C programs -- it is simply included as an external variable much 
like RPG IMPORTs variables.  

However, there are exceptions.  The Unix and C run-time routines sometimes 
return negative values to indicate failure, sometimes a NULL pointer 
indicates failure, sometimes no indication at all! And sometimes they are 
completely confused and return an unsigned integer yet state -1 indicates an 
error ....

The system() function returns zero if it worked, -1 if you pass a NULL 
string, and 1 as a failure indicator.  If the return code is 1 then the 
_EXCP_MSGID global variable will contain the message ID (generally a CPF 
message) indicating the failure reason.

I only use system() when I know the command will work (e.g., OVRxxx, etc).  I 
use the QCAPCMD API for all other instances.

Regards,
Simon Coulter.

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