I've been playing with OpenCOBOL today. In particular, I wanted to figure out two things: 1) how to access environment variables, and 2) how to call an external C function and pass parameters. Here is an example. First, the COBOL code (Updated 2019/07/20, to work with GNU Cobol 1.1.0):

       IDENTIFICATION DIVISION.
       PROGRAM-ID. CALLENV.
       DATA DIVISION.
       WORKING-STORAGE SECTION.
       01 ENVVAR.
          05 PIC X(1024).
          05 PIC X X"00".
       01 RETVAL PIC 9(9).
       01 RETVALZ PIC Z(08)9.
       01 TIMESVAL USAGE BINARY-LONG VALUE 111.
       PROCEDURE DIVISION.
       ACCEPT ENVVAR FROM ENVIRONMENT "COBENV".
       CALL "print" USING ENVVAR, BY VALUE TIMESVAL RETURNING RETVAL.
       MOVE RETVAL TO RETVALZ.
       DISPLAY 'Return value is ' FUNCTION TRIM(RETVALZ,LEADING) '.'.
       STOP RUN RETURNING 0.

Next, the external C function:

#include <stdio.h>
#include <string.h>

extern int print(char *what, int times)
{
        while (strlen(what) > 0 && what[strlen(what) - 1] == ' ')
                what[strlen(what) - 1] = 0;
        printf("%s, %d times.\n", what, times);
        return 123;
}

The two can be compiled and linked together (and tested) as in the following make file:

callenv:        callenv.cob cobprint.c
        cc -c cobprint.c
        cobc -x -o callenv callenv.cob cobprint.o
        rm cobprint.o
        COBENV="THIS IS A TEST" callenv

I am impressed by OpenCOBOL 1.0. Version 1.1 will be even nicer, I expect.

Incidentally, OpenCOBOL also has an awesome reference manual.