Since I’m a mainframe guy I’ve spent most of my career writing REXX whenever I needed a quick script which means that I know REXX pretty well. Lately I’ve been playing with REXX on Windows thanks to an implementation of REXX called Regina Rexx, see here.
Of course, one of the things you can do on Windows is drag and drop so I wanted to be able to drop a file onto a Regina REXX program and have the REXX program then process the file.
Typically you access input parms in a REXX exec by using the “parse arg varname” statement but I found that this did not work when dropping a file onto a Rexx exec on my Windows machine.
After some research I found that I needed to create a shortcut to the Regina REXX.EXE program with a parameter that is the path and name to the REXX program to run. You then have to drop your files onto the SHORTCUT.
So let’s say I have the following exec called “test.rexx” on my desktop:
parse arg parms say parms say "Press enter to end" parse pull .
I then create a shortcut on my desktop that looks like this:
"C:\Program Files\rexx.org\Regina\rexx.exe" "C:\Users\ltlfrari\Desktop\test.rexx"
So if I drop a file called “test.txt” onto the shortcut, this is the output that I see:
Basically the exec receives the full path and file name as an input argument.
If you’ve ever read or written a macro you have no doubt at least seen conditional assembly language. It’s all that AIF and AGO stuff that forms a sort of ‘program’ within the macro so that it can generate code or whatever depending on whatever the input parameters are.
What’s really cool though is that it is not just limited to macros, you can use it within open code as well. So you might ask ‘why would you need to do that?’ but even if you don’t ask, here’s one interesting situation that came up recently.
I had some code that used a macro to generate a DSECT to map a control block. However we were switching version of the product that supplied the macro and a field within the macro had changed names even though it’s content had not. The result was that my code would only assemble with one version of the macro since with the other one it would get a not found error for the changed label. Since I did not want to have to co-ordinate my source code change with a build tool change the problem I had was how to make my source code support both versions of the macro and DSECT that it generated?
In case you have not guessed, the answer is conditional assembly language.
Here’s an example.
The old macro/DSECT:
MYMACRO SOMENAME DSECT MYFIELD DS CL8
The new version of the macro/DSECT
MYMACRO SOMENAME DSECT NEWNAME DS CL8
So my code originally looked something like this:
USING SOMENAME,R2 CLC MYFIELD,=CL8'AAAAAAAA'
Obviously if I switch to the new macro library, my assembly will fail since the field ‘MYFIELD’ is no longer defined within the DSECT.
However, what you can do is to test to see if the variable ‘MYFIELD’ is defined and if not then conditionally change the code that gets assembled. Thus:
USING SOMENAME,R2 AIF (T'MYFIELD EQ 'U').NEWMAC CLC MYFIELD,=CL8'AAAAAAAA' AGO .CONT .NEWMAC ANOP CLC NEWNAME,=CL8'AAAAAAAA' .CONT ANOP
The AIF tests to see if the ‘type’ specification for the field MYFIELD is ‘U’, that is undefined. If it is undefined that means it has not been seen by the assembler (yet) so jump to the label .NEWMAC and continue to generate the code from there, which of course generates the code using the new field label of NEWNAME.
If the field MYFIELD is not ‘undefined’ then the assembler generates the code using the old field name, MYFIELD and then jumps (AGO) to the label .CONT to continue the assembly.
As a result, no matter which version of the macro library I am using, my code still assembles and works correctly.
There are other ways of achieving the same effect; For example by using the conditional assembly language to control the redefining of the old or renamed symbol to a common name and using that common name in the open code.
One gotcha though to be aware of. The macro/DSECT has to be defined in the source code BEFORE the conditional assembly code. If it is defined after the conditional code then, since the assembler has not seen either field at the time it encounters the test for the field being defined, it will always treat it as being undefined which would cause an assembly error when using the old macro/DSECT library because it would generate the code to use the new field name.
I shall be at Share in Orlando next week so if you seem me (picture on my about page), please do say hi.
During my daily work I often need to copy members from one PDS to another. The Partitioned data sets are always the same ones, just different members. I could use the ISPF Move/Copy Utility screens but it quickly gets tiresome to have to keep entering the data set and member information into the screens.
Since I’ve got my REXX library allocated to SYSPROC so that I can run execs from it directly using the TSO execname command on the ISPF command line I put together the following exec called COPYMBR to automate the process:
/* rexx */ /* exec to copy a member from one pds to another */ parse arg frommbr tombr '/' repl tombr = strip(tombr) upper repl if frommbr = '' then do say "Syntax is COPYMBR from_mbr [to_mbr] [/r]" say "Specify to_mbr name to rename the copied member" say "Specify /r to replace the member in the target PDS" return 0 end if tombr='' then tombr=frommbr if length(frommbr) > 8 then do say "Source member name greater than 8 chars" return 0 end if length(tombr) > 8 then do say "Target member name greater than 8 chars" return 0 end address ispexec "CONTROL ERRORS RETURN" indsn="'"userid()||".LOAD'" /* Source PDS */ outdsn="'"userid()||".LOAD2'" /* Target PDS */ "LMINIT DATAID(IN) DATASET("indsn") ENQ(SHR)" "LMINIT DATAID(OUT) DATASET("outdsn") ENQ(SHR)" opt='' if repl = 'R' then opt = "REPLACE' "LMCOPY FROMID("in") FROMMEM("frommbr") TODATAID("out") ", "TOMEM("tombr") "opt lastcc=rc ins='' if lastcc = 0 then nop else if lastcc=12 then do if frommbr <> tombr then ins = 'as '||tombr say frommbr' not copied'||ins say tombr' already exists on target library.' end else if lastcc=8 then do say frommbr' not found in source library.' end else do say 'rc from LMCOPY='lastcc end "LMFREE DATAID("in")" "LMFREE DATAID("out")" return 0
You can edit the lines marked “Source PDS” and “Target PDS” to specify any compatible load libraries. I just used my LOAD and LOAD2 libraries as an example.
The general syntax of the COPYMBR command on the ISPF command line is then:
TSO COPYMBR member_name [new_name] [/r]
member_name is the name of the member to copy from the source PDS
new_name is optional and is the new name to assign to the member on the target PDS. If not specified it defaults to the same name as the source member.
/r tells the exec to replace the member (or new member name if renaming) on the target PDS.
Note that when the copy is successful, the exec does NOT output any messages so there’s no need to press the enter key to clear a message except when there is something wrong.
TSO COPYMBR MYPROG1 /r
Copy MYPROG1 from the source PDS to the target PDS and replace any existing version.
TSO COPYMBR MYPROG1 MYPROG2
Copy MYPROG1 from the source PDS to the target PDS and rename it to MYPROG2. Do not do the copy if MYPROG2 already exists on the target PDS.
TSO COPYMBR MYPROG1 MYPROG2 /r
Copy MYPROG1 from the source PDS to the target PDS and rename it to MYPROG2. Replace any existing version of MYPROG2 on the target PDS.
One of the things I like to do is to allocate my own REXX library to SYSPROC at TSO logon time so that I can execute REXX commands simply by typing in “TSO command_name” on the ISPF command line.
On the TSO logon screen I have a command setup to invoke a REXX exec that will do that for me:
BEFORE just says to allocate my REXX library before the existing allocations so that anything in my library overrides anything in the existing allocation with the same name (useful for testing changes to existing EXECs). Specify ‘AFTER’ or let it default to allocate your library AFTER the existing allocations.
This is the exec (called ALLOCREX in the above screen shot):
/* rexx */ /* logon exec to concat my rexx library to SYSPROC so that */ /* I can run my own rexx commands easily without having */ /* to specify the dataset name. EG TSO MYEXEC */ /* */ parse arg opt /* BEFORE or AFTER (default) */ lib=userid()||".REXX" /* dsn of rexx lib to alloc */ if x> 4 then do say "Unable to locate '"lib"'." say 'SYSPROC alloc not changed.' signal exit end rc=ddns('SYSPROC') /* get current SYSPROC allocation */ /* extract dsns and check for my rexx lib already alloc */ list='' comma='' do while queued() > 0 parse pull dsn if dsn=lib then do say lib 'already concat to SYSPROC.' say 'SYSPROC alloc not changed.' signal exit end list=list||comma||"'"||strip(dsn)||"'" comma=',' end oldlist=list /* add my rex lib to the list and realloc the DD */ if opt = 'BEFORE' then do list="'"lib"',"||list end else do list=list||",'"lib"'" end "ALLOC F(SYSPROC) DATASET("list") SHR REUSE" allocrc=rc if allocrc <> 0 then do say 'Alloc of SYSPROC faiuled with rc='allocrc say 'Restoring original allocation' "ALLOC F(SYSPROC) DATASET("oldlist") SHR REUSE" end /* queue an ISPF command so this exec can end */ exit: queue 'ISPF' return 0 /*---------------------------------------------------------*/ ddns: procedure /*---------------------------------------------------------*/ /* Find dsns allocated to a specified ddname */ /* Output returned on the stack */ /*---------------------------------------------------------*/ /* */ parse arg ddname upper ddname x=outtrap("out.","*","noconcat",1) address TSO 'listalc status' if out.0 = 0 then do return 0 /* Nothing found */ end foundDD="N" do i=1 to out.0 by 2 parse var out.i dsn . j=i+1 ddn=strip(substr(out.j,3,8)) if ddn <> "" & ddn = ddname then foundDD="Y" if ddn <> "" & ddn <> ddname then foundDD="N" if foundDD = "Y" then do push dsn end end return 0
I know I have not posted anything here for almost a year but I have not died! I’ve just been very busy learning new products and product architectures.
I have to say though that it has been are really fabulous year for me that I have thoroughly enjoyed. With a bit of luck (and time) I’ll get back to posting a few things from time to time here.
It’s been a lot a fun working at IBM and I’ve had the opportunity to work with some truly amazing people and software products over the years but there comes a time when you have to look beyond the ‘safe’ zone and to take that leap of faith. It’s been quite a while since I’ve taken this sort of leap but I have to announce that today, I have left IBM and will be starting a new adventure very soon.
I hope to continue to post to this blog but obviously the topics for the most part will change although they will continue to be mostly about mainframe topics. So I hope that you, my few readers, continue to find something of interest here that will lure you back from time to time.