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bcmohanty
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Joined: 17 May 2006
Posts: 17
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| How to display the 3rd record from the last of a sequential file (not know the no. of records). (Thru Cobol Prog) |
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DavidatK
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Joined: 22 Nov 2005
Posts: 700
Location: Troy, Michigan USA
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bcmohanty,
I think you?re going to have to create a Cobol table occurs 3 times and every time you read a record, push the entries in the table down and add the new record at the top. When an EOF occurs the (3) entry will be you?re third from last.
| Code: |
FD INPUT-FILE
01 INPUT-RECORD PIC X(80).
WORKING-STORAGE.
01 INPUT-TABLE.
05 INPUT-REC PIC X(80) OCCURS 3 TIMES.
PROCEDURE-DIVISION.
PERFORM READ-INPUT-RECORD.
PERFORM
UNTIL INPUT-RECORD-EOF
MOVE INPUT-REC(2) TO INPUT-REC(3)
MOVE INPUT-REC(1) TO INPUT-REC(2)
MOVE INPUT-RECORD TO INPUT-REC(1)
PERFORM READ-INPUT-RECORD
END-PERFORM.
DISPLAY INPUT-REC(3).
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Dave |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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If this is more than just an intellectual exercise, I'd opt for using the FileAid COPYBACK feature, then accessing the rec from this output.
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//COPYREC EXEC PGM=FILEAID
//DD01 DD DSN=input.dsn,DISP=SHR
//DD01O DD DSN=output.dsn,DISP=SHR
//SYSIN DD *
$$DD01 COPYBACK SELECT=3,OUT=1
//SYSPRINT DD SYSOUT=A
//*
//NEXT EXEC PGM=yrpgm
//HIGHREC DD DSN=file.contains.3rd.high.rec
//etc.... |
You can use CB in place of COPYBACK. COPYBACK works for VSAM and seq files, but not GDGs. |
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hikaps14
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Joined: 02 Sep 2005
Posts: 189
Location: Noida
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Hi,
According to me just do a sort on file in reverse order .
then read the file three times .
i hope u get the approach .
Thanks,
-Kapil . |
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DavidatK
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Joined: 22 Nov 2005
Posts: 700
Location: Troy, Michigan USA
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The question was:
How to display the 3rd record from the last of a sequential file (not know the no. of records). (Thru Cobol Prog)
Dave |
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hikaps14
Active User
Joined: 02 Sep 2005
Posts: 189
Location: Noida
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Hi,
wel i think u misunderstood a bit .
wat i want to do is just sort the file in reverse order.
this will bring the third last record in file to no. 3 p[osition from top .
n now we can easily read n get the third record from top .
i hope i got the prob. correctly .
or is it completely diff. prob.
plz do tell me if i am wrong .
-Thanks,
Kapil . |
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vijayamadhuri
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Joined: 06 Apr 2005
Posts: 180
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| Quote: |
| How to display the 3rd record from the last of a sequential file (not know the no. of records). (Thru Cobol Prog) |
using Sort reverse the file and use this file as i/p . increment the counter as it reads each record and u would print only if it the third record |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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The problem with these solutions is reading the entire file to "display" the rec.
The FileAid solution uses an Assembler reverse read. If this were a real world problem Assembler or some more direct access to the record would be the preferred approach. |
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gskulkarni
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Joined: 01 Mar 2006
Posts: 70
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| mmwife wrote: |
| The problem with these solutions is reading the entire file to "display" the rec. |
However, in the first post (s)he has mentioned [quote="bcmohanty"](Thru Cobol Prog)[quote="bcmohanty"]
So,
If the file is in specific sort order: I guess people have suggested a very good option of sorting the file in reverse order and reading the first 3 recs. 3rd one can be displayed.
Otherwise, if the file is unsorted and records are not in a particular sort order:
1) If you have to use cobol program, then you can do a IDCAMS COUNT and store the result in a dataset. In your COBOL prog read that dataset and get the count-4. Skip as many records and display your record number 3 from 'down'!
2) Fileaid solution serves the purpose right. (This is the best one!!)
So if the file is sorted |
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mmwife
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Joined: 30 May 2003
Posts: 1592
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If the file is small then I guess it's OK to read the file, but sorting the file, from a performance perspective, is the worst solution regardless of the file's size.
I don't know why this kind of thing would have to be done; it sounds like faulty system design. |
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sharda
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Joined: 13 Sep 2006
Posts: 7
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Hi Davidatk,
I reffer ur following code but as I am fresher in this field, I am not able to get the following code exactly . Can u plz explain the code in detail (from beginning to end ) .
FD INPUT-FILE
01 INPUT-RECORD PIC X(80).
WORKING-STORAGE.
01 INPUT-TABLE.
05 INPUT-REC PIC X(80) OCCURS 3 TIMES.
PROCEDURE-DIVISION.
PERFORM READ-INPUT-RECORD.
PERFORM
UNTIL INPUT-RECORD-EOF
MOVE INPUT-REC(2) TO INPUT-REC(3)
MOVE INPUT-REC(1) TO INPUT-REC(2)
MOVE INPUT-RECORD TO INPUT-REC(1)
PERFORM READ-INPUT-RECORD
END-PERFORM.
DISPLAY INPUT-REC(3).
Thks
Sharda |
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prashanth1
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Joined: 27 Sep 2006
Posts: 47
Location: Hyderabad
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Hi,
We can achieve this by reading the file in reverse order
Syntax : OPEN INPUT file-name REVERSED
Here it opens the file in reverse direction
Just put one counter variable , when the counter variable becomes 3, just write that record into output file.
Pls let me know , If I wrng  |
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Arun Raj
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Joined: 17 Oct 2006
Posts: 2481
Location: @my desk
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OPEN INPUT file-name REVERSED
plz let me now if this statement can be used for all type of files(disk/tape)
regards
sanooja [/quote] |
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DavidatK
Active Member
Joined: 22 Nov 2005
Posts: 700
Location: Troy, Michigan USA
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This can be used only on tape files, and I believe it's going to be obsolete in the next Cobol release
Dave |
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