Michael Stein,
You are right. Thank very much for pointing to the mistake.
I was trying to read file using "with open as". This way I was expecting to
pull single record at every iteration of loop.
With your suggestion, I opened entire file in memory and read each record based
on record length in RDW. Now I can read each record as expected.
Once again thank you to all member for taking time to read my query and
responding. Its good learning.
Thank you,
Prashant Joshi
-----Original Message-----
From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of
Michael Stein
Sent: Tuesday, May 16, 2023 11:56 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: [EXTERNAL] Re: VBS file read in windows - end of record issue
On Tue, May 16, 2023 at 04:14:07AM +0000, Prashant Joshi wrote:
>> Did you specify binary mode on the python open call? --
> Yes. And I can read the data.
How are you reading the data. Assuming an open like:
myfile = open("filename", "rb")
You need to either read it all into memory:
alldata = myfile.read()
or read specific lengths which is messier as you need to read specific lengths,
first 4 bytes for the RDW and then the length of the record in the RDW-4 (as
you already read the RDW).
The 4 byte RDW includes the length of the record in the first 2 bytes
(bigendian order) and the spanning bits in the last 2 bytes.
Either way you need to walk your way through the binary data, any code looking
for CR or NL or space isn't correct.
A description of VBS records formats:
z/OS 2.4 DFSMS Using Data Sets SC23-6855-40
https://www-40.ibm.com/servers/resourcelink/svc00100.nsf/pages/zOSV2R4sc236855/$file/idad400_v2r4.pdf
pdf page 273 Variable-Length Record Formats (near bottom of page and continues
on to more pages)
> its just that I don't get proper end of reord. Hence every time I read
> record, I get random record length (multiple records/half records
> combined)
There aren't any "end of records" in a VBS file. At the begining of the file
you know you are at the start of a RDW (Well, BDW/RDW but I'm assuming the FTP
removed the BDWs).
You can find the next record by going the length specified in the RDW into the
file -- that is the start of the next RDW. Continue until you've processed all
the records.
More help will likely require you to show some code and/or data so we can see
what is going on...
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