You can’t code arbirtraty names but a common convention is to look for a key in a file and use the value as a filename. Its a similar approach to DDNAMES as it uses an intermediary, just not as well defined for all users.
Matt Hogstrom PGP key 0F143BC1 > On Jan 7, 2022, at 13:37, Charles Mills <[email protected]> wrote: > > FWIW yes, I go back to > > A little bit of CP/67 and OS/360 on a 360/67 in 1967 > Hardcore DOS/360 on 360/40s and /50s starting in 1968 (My first paid > software job.) > Hardcore OS/360 starting around 1972 or so. No SVC 99! > > And I disagree. Variables and file handles are not the same as DD names at > all. I can hard-code a z/OS program to copy 'MYFILE1' to 'MYFILE2'. It can > then copy any dataset to any other dataset (with many limitations, but you > get the idea). > > There is no directly equivalent function in Windows or Linux. I cannot code > arbitrary internal names (in variables or otherwise) and then map them to > real external names at run time. (AFAIK -- correct me if I am wrong. Yes, > stdin and stdout come close.) > > Charles > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Seymour J Metz > Sent: Friday, January 7, 2022 9:52 AM > To: [email protected] > Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS > > I would say that what substitues for ddnames is variables and file handles. > > You go back to OS/360? > > > -- > Shmuel (Seymour J.) Metz > http://mason.gmu.edu/~smetz3 > > ________________________________________ > From: IBM Mainframe Discussion List [[email protected]] on behalf of > Charles Mills [[email protected]] > Sent: Friday, January 7, 2022 10:16 AM > To: [email protected] > Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS > > A file handle is basically a DCB, or rather, a pointer to a DCB. The thing > it points to is a black box, so there are no compatibility issues comparable > to the 24-bit addresses in DCBs. > > What "substitutes" for DD name indirection in many or most non-mainframe > systems is that "dynamic allocation" is standard. I remember the days before > SVC 99. It was something of a hack job to write a program that decided on a > dataset name during execution. OTOH for most non-mainframe operating systems > the standard way to specify a file at open time is by external file name. If > you are going to prompt the user for a file name during execution (as most > interactive programs do) then file name indirection would be > counterproductive. > > Charles > > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Bob Bridges > Sent: Friday, January 7, 2022 6:47 AM > To: [email protected] > Subject: Re: ... Re: Top 8 Reasons for using Python instead of REXX for z/OS > > Took me an embarrassingly long time to notice that what I thought was silly > in some of the non-mainframe programming languages I'd encountered, the > feature called a "file handle", allowed programs in those languages the same > flexibility that DD names give in JCL. > > --- > Bob Bridges, [email protected], cell 336 382-7313 > > /* Democracy is the recurrent suspicion that more than half of the people > are right more than half of the time. -E B White */ > > -----Original Message----- > From: IBM Mainframe Discussion List <[email protected]> On Behalf Of > Tom Brennan > Sent: Friday, January 7, 2022 00:13 > > Maybe a bigger issue is with non-mainframe folks wondering why JCL is there > in the first place. I started with microcomputers, programming things in > BASIC where we were told to hard-code full filenames in the program itself. > Already I could see how silly that would be in production, having to change > the source code just to work with different files. Unix solved that in > clever ways with parameter passing, stdin, and things like that which work > well in shell scripts. Mainframes solved it with 8 character DD names and > JCL redirection. > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
