Re: _C_IFS_fopen -- MIDRANGE-L

Does any one use this function in RPGLE?


I use them all the time.

If so, what authorities are required to read a file. I am callingpassing the parm of 'r' which, to the best of my knowledge, is the flagfor read only. The jobs work great if you have *RWX but blow up if youhave *R or *RX only.

Correct. I just tried to re-create your problem by creating a file that Ionly have *R permission to, and it worked just fine, so I'm not sure whatyou're doing differently.

I have been searching IBM great hiding place called InfoCenter with noluck.
What I would really like is the link to the whole _C_IFS_ api's that
shows the necessary authorities.

Okay. I'll explain. These functions (fopen & friends) aren't consideredsystem APIs. ( The system APIs for working with the IFS are open(),read(), etc. ). Instead, the functions that you're trying to call arepart of the ILE C runtime library.

According to the ANSI standards for the C programming language, thereneeds to be a function called fopen() that you can use to open and read afile. If you didn't have that on the iSeries, the iSeries wouldn'tconform to the standards, which wouldn't be good.

So, IBM created an fopen() function that worked with the standardlibrary/file scheme, compatible with what you can do with F-specs in RPG.

Then, later, IBM created the IFS. This made it easier for people portingC software from Windows or Unix because the IFS stores stream files in thesame way. Those people were using fopen() to read stream files onWindows/Unix, so it's desirable for them to use the same functions here onthe iSeries. But, fopen() already exists! And it's not for the IFS!

So they added a compiler option. If you specify SYSIFCOPT(*IFSIO) on thecompile command, the fopen() function will access the IFS. If don'tspecify that option, it uses the traditional library/object method.

The way they implemented this SYSIFCOPT(*IFSIO) option was by writing twounderlying APIs in the ILE C runtime. One called fopen(), and anothercalled _C_IFS_fopen(). When you specify *IFSIO, it automatically mapsfopen() to the latter.

If you wanted to, you COULD do the same thing in RPG. In RPG the codewould look like this:


      /if defined(USE_IFS_IO)
     D fopen           PR              *   ExtProc('_C_IFS_fopen')
      /else
     D fopen           PR              *   ExtProc('fopen')
      /endif
     D   filename                      *   value options(*string)
     D   mode                          *   value options(*string)

Of course, there's really no reason to use the standard fopen() functionin RPG, since RPG has it's own support for traditional file access. Youonly need the IFS support, since RPG doesn't have that built in.

Now that you understand that, hopefully you understand why you can't find_C_IFS_fopen() in the information center. The documentation is intendedfor C programmers, and they don't think of this function as having thatname... they simply think of it as fopen().


Go into the Information Center and look at

 Programming -> Languages -> C and C++ -> ILE C/C++ Run Time Library Functions

That's the path for V5R3. The paths for earlier versions are similar, butI don't think there was a "Languages" section in older releases. You justgo straight from Programming to C and C++.

Anyway, in that book, look up the fopen() function. (or fclose, fread,fgets, whatever you need.)

Another interesting function is fdopen(). It lets you take a file thatyou've already opened with open(), and upgrade it to work with fgets(),fread(), etc.


Hopefully that helps...