读取文件的最后一条记录

Question

我有一个 COBOL 程序，该程序的每个运行都需要一个事务编号。我打算从文件中获取最后一个交易编号并将其加 1。问题是我不知道如何获取最后记录的值。

IDENTIFICATION DIVISION.
PROGRAM-ID. INVENTORY-SYS.
AUTHOR. LINSEY.
DATE-WRITTEN. 2/22/2015.
DATE-COMPILED. 2/22/2015.

ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
INPUT-OUTPUT SECTION.
    FILE-CONTROL.
    SELECT MASTER-FILE ASSIGN TO "inventory-file.txt"
    ORGANIZATION IS LINE SEQUENTIAL.

DATA DIVISION.
FILE SECTION.
FD MASTER-FILE.
01 IN-RECORDS.
    02 IN-CODE PIC 9(7).
    02 IN-NAME PIC X(30).
    02 IN-PRICE PIC 9(3).
    02 IN-STOCK PIC 9(4).

WORKING-STORAGE SECTION.
01 WS-EOF PIC A(1).

PROCEDURE DIVISION.
100-READ-FILE.
OPEN I-O MASTER-FILE.
PERFORM UNTIL WS-EOF = "Y"
READ MASTER-FILE
 AT END
      MOVE 'Y' TO WS-EOF
 NOT AT END
    DISPLAY IN-RECORDS
END-READ
END-PERFORM
CLOSE MASTER-FILE.
STOP RUN.

这是示例程序。问题是它从文件中检索所有记录我只检索 "inventory-file.txt"

中的最后一条记录

Answer 1

嗯，你很坚持，所以：

IDENTIFICATION DIVISION.
PROGRAM-ID. INVENTORY-SYS.

ENVIRONMENT DIVISION.
CONFIGURATION SECTION.
INPUT-OUTPUT SECTION.
    FILE-CONTROL.
    SELECT MASTER-FILE ASSIGN TO "inventory-file.txt"
    ORGANIZATION IS LINE SEQUENTIAL
    FILE STATUS IS w-if-in-file-status.

DATA DIVISION.
FILE SECTION.
FD MASTER-FILE.
01 IN-RECORDS.
    02 IN-CODE PIC 9(7).
    02 IN-NAME PIC X(30).
    02 IN-PRICE PIC 9(3).
    02 IN-STOCK PIC 9(4).

WORKING-STORAGE SECTION.
01  w-if-in-file-status PIC XX.
    88  master-file-status-good VALUE ZERO "10".
    88  end-of-master-file VALUE "10".
01  w-save-code PIC 9(7).

PROCEDURE DIVISION.
    OPEN INPUT MASTER-FILE
    [code to check FILE STATUS field]
    PERFORM UNTIL end-of-master-file
        READ MASTER-FILE
        [code to check FILE STATUS field]
        MOVE IN-CODE to w-save-code
    END-PERFORM
    DISPLAY ">" w-save-code "<"
    CLOSE MASTER-FILE
    [code to check FILE STATUS field]
    GOBACK
    .

我不知道为什么您的 IN-CODE 字段是数字。你要用它做计算吗？

您保留了一个控制文件。具有日期（与业务日期文件匹配）、逻辑文件名、环境和最后交易编号。

您维护该文件，同时检查所有内容。

Answer 2

我不确定 OpenCobol 是否支持它，但您可以尝试使用 OPEN/REVERSED。这是一种向后读取磁带的老式方法，或者现在是虚拟磁带。我不知道它是否已实现，但它是一种向后读取顺序文件的简单方法。

读取文件的最后一条记录

Reading the last record of a file

cobol