如何从RPG程序创建新的文件成员？

Question

I need to create a new member for an existing physical file in my RPG-program. I know of two ways, and I must say, that I like neither:

1. use QCMDEXC to make a call to ADDPFM
2. write an CL-program, that calls ADDPFM and call that from RPG

The first one involves cat'ing together a command that has to be parsed by QCMDEXC which does not sound to performant (I know, the expansive part here is not the call, but the creation of the member) -- but what bothers me really about it, is that I don't find it straightforward, but on the contrary hard to follow and not very aesthetic.

The second one uses a compiled program, so there is no concating and parsing involved. Also, it does not look that horrible in your RPG-code, because it is only one normal procedure call. But I'll have to create an extra external program, that need's to be transfered to all systems my RPG-program will be used on. It also kind of conflicts with my sense of aesthetics, creating an extra source and binary just to do one api call.

Is there a way to call the api directly, without QCMDEXC ? Or maybe another RPGish way of creating a new member to a PF? Google was no help to me at all..

Thanks

Answer 1

There is no way to directly create a physical file member from within RPG.

The options you listed are good. Another is the system() API. If this is a new app, try to avoid multiple members; they are not friends with SQL. Traditional multi-member apps use a wrapper CL to handle the ADDPFM and OVRDBF before calling the RPG:

PGM &month
DCL &month *char 3
DCL &mbr *char 10
chgvar &mbr ('SALES' *cat &month)
addpfm sales &mbr
monmsg...
ovrdbf sales mbr(&mbr)
call RPG_PGM
endpgm

Obviously, with more recent versions of RPG, we can do the overrides in the F specs. But there is still no way to manipulate file members directly from within RPG. I tend to write procedure wrappers for system() or QCMDEXC and put that in a service program so I can do OS-level work from within my RPG programs. If you prefer, write a specific ADDPFM procedure and call that 'API'.

Answer 2

To give some example of the QCMDEXC solution. If you just need some way within an RPG-program to create a member, and you don't want to add any additional (CL-)programs, this is a simple solution that does the job:

You can create a procedure crt_mbr like this:

 Pcrt_mbr          B
 D                 PI
 D lib                           10A   value
 D file                          10A   value
 D mbr                           10A   value
 Dqcmdexc          PR                  extpgm('QCMDEXC')
 D str                          200a   options(*varsize) const
 D len                           15P 5 const
 Dcmd              S            200A
 Dlen              S             15P 5
  /free
   cmd = 'ADDPFM FILE('+%trimr(lib)+'/'+%trimr(file)+') ' +
         'MBR(' + %trimr(mbr) +')';
   len = %len(%trimr(cmd));
   qcmdexc(cmd: len);
  /end-free
 Pcrt_mbr          E

It can look like this in v7:

dcl-proc crt_mbr;
  dcl-pi *n;
    lib    char(10) value;
    file   char(10) value;
    mbr    char(10) value;
  end-pi;

  dcl-pr qcmdexc  extpgm('QCMDEXC');
    str    char(200) options(*varsize) const;
    len    packed(15:5) const;
  end-pr;

  dcl-s cmd    char(200) inz('');
  dcl-s len    packed(15:5) inz(0);

  cmd = 'ADDPFM FILE(' + %trimr(lib) + '/' + %trimr(file) + ')' +
        ' MBR(' + %trimr(mbr) + ')';
  qcmdexc(cmd: %len(%trimr(cmd)));
end-proc;

You might need to add the prototype at the beginning of your program (depending on your release):

 Dcrt_mbr          PR
 D lib                           10A   value
 D file                          10A   value
 D mbr                           10A   value

Know in your program you can just call:

/free
 ...
 crt_mbr('MY_LIB': 'MY_FILE': 'NEW_MEMBER');
 ...
/end-free

Please notice, that this has no error handling at all. So if eg the file allready contains a member of that name, your program will dump. Add monitoring or different error handling as needed.