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  • Pointer question

    In a RPG program if I have a physical file that is my primary read and have a logical file over that physical file. If the logical file is read will I lose my main pointer to my physical file?

    DAC

  • #2
    Re: Pointer question

    no you wont.......
    All my answers were extracted from the "Big Dummy's Guide to the As400"
    and I take no responsibility for any of them.

    www.code400.com

    Comment


    • #3
      Re: Pointer question

      Actually as Jamie said, if you read the LF after the PF, you do not lose the pointer to the PF but you jeopardize the previously data read.
      Philippe

      Comment


      • #4
        Re: Pointer question

        Won't the field names be the same for the logical and physical? This means the pointer will still be there but the data would not. (As Mercury pointed out)

        There's a couple of solutions.
        1.
        You could perform the read into a datastructure so they would be writing to different variables
        PHP Code:
        D filerec         ds                  likerec(filer:*input)     
         /
        free
         read file filerec
        ;
         if 
        filerec.field =' '
        2.
        You could prefix the field names in the F specs
        PHP Code:
        FFILE      UF A E           K DISK             
        FFILE01    UF A E           K DISK    RENAME
        (FILER:FILE01RPREFIX(l
        Ben

        Comment


        • #5
          Re: Pointer question

          Originally posted by BenThurley View Post
          Won't the field names be the same for the logical and physical? This means the pointer will still be there but the data would not. (As Mercury pointed out)

          There's a couple of solutions.
          1.
          You could perform the read into a datastructure so they would be writing to different variables
          PHP Code:
          D filerec         ds                  likerec(filer:*input)     
           /
          free
           read file filerec
          ;
           if 
          filerec.field =' '
          2.
          You could prefix the field names in the F specs
          PHP Code:
          FFILE      UF A E           K DISK             
          FFILE01    UF A E           K DISK    RENAME
          (FILER:FILE01RPREFIX(l
          FWIW i use both techniques depending on the purpose/intent of the application. i recommend trying both and then you can decide which is better suited for your program/application. more and more i'm leaning toward the data structure method so i can use eval-corr, etc.
          I'm not anti-social, I just don't like people -Tommy Holden

          Comment


          • #6
            Re: Pointer question

            Originally posted by tomholden View Post
            FWIW i use both techniques depending on the purpose/intent of the application. i recommend trying both and then you can decide which is better suited for your program/application. more and more i'm leaning toward the data structure method so i can use eval-corr, etc.
            Also, you have to use data structures in order to use files within subprocedures, so its basically the wave of the future.

            And since IBM has added support for data structures on the EXFMT statement, it makes it really easy to move fields from a file to display file or to work fields while only using a single line of code via the eval-corr statement.
            Michael Catalani
            IS Director, eCommerce & Web Development
            Acceptance Insurance Corporation
            www.AcceptanceInsurance.com
            www.ProvatoSys.com

            Comment


            • #7
              Re: Pointer question

              Originally posted by MichaelCatalani View Post
              Also, you have to use data structures in order to use files within subprocedures, so its basically the wave of the future.
              How is this the case? I agree it's better to use data structures but I didn't think it was a necessity.
              Ben

              Comment


              • #8
                Re: Pointer question

                Originally posted by BenThurley View Post
                How is this the case? I agree it's better to use data structures but I didn't think it was a necessity.
                it's not a necessity, heck if you want you can pass the entire record as a single field and parse it out adhoc but DS is much better in v6.1 you can simply pass file handles/pointers rather than using a DS but unless you are using files local to the subproc i really don't see much sense in going that route.
                I'm not anti-social, I just don't like people -Tommy Holden

                Comment


                • #9
                  Re: Pointer question

                  Files defined in a subprocedure do not have an input / output buffer included automatically by the program. You must describe a data structure for the file and then include that data structure on subsequent reads or writes for the file. While that may sound a bit cumbersome, it actually saves a lot of coding, especially if you have work fields involved.
                  Michael Catalani
                  IS Director, eCommerce & Web Development
                  Acceptance Insurance Corporation
                  www.AcceptanceInsurance.com
                  www.ProvatoSys.com

                  Comment


                  • #10
                    Re: Pointer question

                    After re-reading my initial post, it may not be clear that I was referring to files defined on F-specs within a subprocedure. Those files need to have data structures defined for them, as they have no input / output buffers automatically created by the compiler.
                    Michael Catalani
                    IS Director, eCommerce & Web Development
                    Acceptance Insurance Corporation
                    www.AcceptanceInsurance.com
                    www.ProvatoSys.com

                    Comment


                    • #11
                      Re: Pointer question

                      Ahh I see. I wasn't aware you could define F specs within a sub-procedure. Unless perhaps you are talking specifically of the new 6.1 feature? Our service programs define them at the top.
                      Ben

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