CRC checksum in DFSORT

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

Does DFSORT has anything like this?
en.wikipedia.org/wiki/Cyclic_redundancy_check

with the crc checksum each record in a file gets a unique value

When you change the file and run the crc checksum again, you can see quickly which records have been changed, because there checksum is different

Frank Yaeger · Posted: Wed Nov 19, 2008 2:06 am

DFSORT does not have a built-in function like that. However, DFSORT can do arithmetic so perhaps you could "roll your own" (or perhaps not).

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

Then you should know the algorithm inside the CRC checksum, I think Frank. Unfortunately I don't know.
I will go on searching
thanks

dick scherrer · Posted: Wed Nov 19, 2008 2:59 am

Hello,

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

don't over-react
maybe i shhould have said: "Then I should know ... ."
Is a check digit the same?
I want to compare the file of today with yesterday and see if something is changed

enrico-sorichetti · Posted: Wed Nov 19, 2008 4:26 am

here is a link to a bit of CRC philosophy
www.geocities.com/SiliconValley/Pines/8659/crc.htm

the objective of a check digit is the same..
but the algorithm is quite different and does not to obey a standard
for example check digits are of the general form...
given that a number is

D1 D2 D3 .... Dn 0 < Dx < 9

the the check digit(s) is/are usually calculated by
( D1*M1 + D2*M2 + D3*M3 + ... + Dn*Mn ) MODULO M
0 < Mx < 9

dick scherrer · Posted: Wed Nov 19, 2008 8:03 am

Hello,

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

Dick,

you say : If all you want is a check-digit, you can write your own. . .

How do I write a general check-digit? If I want to compare two records of FB 80?

dick scherrer · Posted: Thu Nov 20, 2008 7:38 am

Hello,

I am probably mis-understanding something, but if you have 2 sets of records that do not already have a check-digit, is there a reason to use something other than SUPERC?

If the records already have a check-digit. . . ?

As i mentioned, i am probably mis-understanding something. . .

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

the records don't have a chkdigit
superc is not allowed in production
I need to know which records have been changed

Alain Benveniste · New User Joined: 14 Feb 2005 Posts: 88

revdpoel,

Did you go to the "Smart DFSORT Tricks" paper at:

Use [URL] BBCode for External Links

and took a look at:

Create files with matching and non-matching records

You could find your solution ...

Alain

revdpoel · New User Joined: 01 Nov 2006 Posts: 56

thank you

dick scherrer · Posted: Fri Nov 21, 2008 4:33 am

Hello,

FWIW, posting a requirement is usually more productive than posting a question about some potential solution for an undefined requirement.

I suspect that had the question originally been about how to compare 2 files rather than about implementing check digit/crc logic, Frank would have originally replied with something quite similar to what Alain posted.

I only mention this as it might have saved you couple of days

Frank Yaeger · Posted: Fri Nov 21, 2008 7:10 am

Excellent point, Dick.

This kind of thing seems to happen quite often. Somebody gets a notion in their head about how something could be done and asks the wrong question leading to confusion and wasted time. Much better to describe the requirement in detail with examples so the "best" solution can be suggested.