Read STDIN (SYSIN) in COBOL

Question

I want to read the lines out of STDIN (aka SYSIN) in COBOL. For now I just want to print them out so that I know I've got them. From everything I'm reading it looks like this should work:

  IDENTIFICATION DIVISION.
  PROGRAM-ID. APP.

  ENVIRONMENT DIVISION.
  INPUT-OUTPUT SECTION.
  FILE-CONTROL.
  SELECT SYSIN ASSIGN TO DA-S-SYSIN ORGANIZATION LINE SEQUENTIAL.

  DATA DIVISION.
  FILE SECTION.
  FD SYSIN.
  01 ln PIC X(255).
     88 EOF VALUE HIGH-VALUES.
  WORKING-STORAGE SECTION.
  PROCEDURE DIVISION.
  OPEN INPUT SYSIN
  READ SYSIN
  AT END SET EOF TO TRUE
  END-READ
  PERFORM UNTIL EOF
  DISPLAY ln
  READ SYSIN
  AT END SET EOF TO TRUE
  END-READ
  END-PERFORM
  CLOSE SYSIN
  STOP RUN.

That compiles (using open-cobol and cobc -x), but running it I get:

libcob: File does not exist (STATUS = 35) File : ''

What am I doing wrong?

Answer 1

My COBOL dates back to the DPS-6 minicomputer runnong GCOS-6 and I lasted touched that in 1992. But back then we used ACCEPT to get input from stdin.

Answer 2

The following was suggested to me on the OpenCOBOL forums.

SELECT SYSIN ASSIGN TO KEYBOARD ORGANIZATION LINE SEQUENTIAL.

It's the keyword KEYBOARD that makes it work.

Apparently DISPLAY is a similar word for STDOUT, but I have not tested that.

Answer 3

You can just use the ACCEPT keyword to grab keyboard output. Loop through until you hit a keyword such as 'end', or you can use the hex value of EOF (1A, I believe).

As in:

1000-YOUR-PARAGRAPH.
  ACCEPT WS-YOUR-VARIABLE.
  DISPLAY WS-YOUR-VARIABLE.
  IF WS-YOUR-VARIABLE IS NOT EQUAL TO EOF
    THEN GO TO 1000-YOUR-PARAGRAPH
  ELSE GO TO 1090-EXIT
  END-IF.
1090-EXIT.
  EXIT.

That will take everything up to an EOL marker (e.g. return).