Logging in COBOL

Here’s the translation of the Go logging example to COBOL, with explanations in Markdown format suitable for Hugo:

IDENTIFICATION DIVISION.
PROGRAM-ID. LOGGING-EXAMPLE.

ENVIRONMENT DIVISION.
INPUT-OUTPUT SECTION.
FILE-CONTROL.
    SELECT STANDARD-OUTPUT ASSIGN TO DISPLAY
    ORGANIZATION IS LINE SEQUENTIAL.

DATA DIVISION.
FILE SECTION.
FD STANDARD-OUTPUT.
01 OUTPUT-LINE PIC X(80).

WORKING-STORAGE SECTION.
01 WS-CURRENT-DATE.
    05 WS-YEAR  PIC 9(4).
    05 WS-MONTH PIC 9(2).
    05 WS-DAY   PIC 9(2).
01 WS-CURRENT-TIME.
    05 WS-HOUR   PIC 9(2).
    05 WS-MINUTE PIC 9(2).
    05 WS-SECOND PIC 9(2).
01 WS-TIMESTAMP PIC X(23).

PROCEDURE DIVISION.
MAIN-PROCEDURE.
    PERFORM STANDARD-LOGGER
    PERFORM CUSTOM-LOGGER
    PERFORM FILE-LOGGER
    STOP RUN.

STANDARD-LOGGER.
    PERFORM GET-TIMESTAMP
    DISPLAY WS-TIMESTAMP " standard logger".

GET-TIMESTAMP.
    MOVE FUNCTION CURRENT-DATE TO WS-CURRENT-DATE
    MOVE FUNCTION CURRENT-TIME TO WS-CURRENT-TIME
    STRING WS-YEAR "/" WS-MONTH "/" WS-DAY " "
           WS-HOUR ":" WS-MINUTE ":" WS-SECOND
           DELIMITED BY SIZE
           INTO WS-TIMESTAMP.

CUSTOM-LOGGER.
    PERFORM GET-TIMESTAMP
    DISPLAY WS-TIMESTAMP " my: from mylog".

FILE-LOGGER.
    OPEN EXTEND STANDARD-OUTPUT
    PERFORM GET-TIMESTAMP
    STRING WS-TIMESTAMP " buf: hello"
           DELIMITED BY SIZE
           INTO OUTPUT-LINE
    WRITE OUTPUT-LINE
    CLOSE STANDARD-OUTPUT
    DISPLAY "from buflog: " OUTPUT-LINE.

The COBOL standard library provides straightforward tools for outputting logs from COBOL programs. While it doesn’t have built-in logging packages like in some modern languages, we can implement similar functionality using COBOL’s file handling and display capabilities.

In this example, we’ve created a simple logging program that demonstrates different ways of outputting log messages in COBOL.

1. The STANDARD-LOGGER paragraph mimics a standard logger. It outputs a timestamp followed by a message to the console.

2. The GET-TIMESTAMP paragraph is a utility that generates a timestamp similar to what you’d see in many logging libraries. It uses FUNCTION CURRENT-DATE and FUNCTION CURRENT-TIME to get the current date and time.

3. The CUSTOM-LOGGER paragraph demonstrates how you might create a custom logger with a prefix, similar to creating a new logger instance in other languages.

4. The FILE-LOGGER paragraph shows how to log to a file (in this case, we’re using STANDARD-OUTPUT as a simplification, but in a real scenario, you’d typically use a separate file).

To run the program, you would compile it and then execute the resulting program:

$ cobc -x logging-example.cob
$ ./logging-example

Sample output might look like:

2023/08/22 10:45:16 standard logger
2023/08/22 10:45:16 my: from mylog
from buflog: 2023/08/22 10:45:16 buf: hello

Note that COBOL doesn’t have built-in support for structured logging or JSON output like some modern languages. For such functionality, you would need to implement it manually or use third-party libraries if available for your COBOL environment.

This example demonstrates basic logging concepts in COBOL, adapting the ideas from the original example to fit COBOL’s paradigm and available features.