Problem:
demonstration is attached.
It contains
I) ==================
firts a COBOL code, named pipeCob.cbl,
which uses UNIX primitives: pipe & write and read and close
To WRITE in a pipe & READ from the pipe
II) ==================
A C code named pipeCob.c which
....creates a pipe
....calls COBOL ( CobolWrtPipe.cbl) ) passing to COBOL the pipe File descriptor
... .. .. the Cobol Function writes in the pipe
... Back in C code, the C code, thru the use of the read function, reads the content of the pipe filled by the COBOL function above
Resolution:
I) ==================
Sample Cobol code which uses UNIX primitives pipe & write & read & close to I-O on a pipes
Cob -x pipecob.cbl
pipeCob.cbl
WORKING-STORAGE SECTION.
01 int pic s9(9) comp-5 is typedef.
01 fildes.
02 fd0Read int.
02 fd1Write int.
01 ret int.
78 ConstBufLen value 100.
78 bufConst value "I-O_on_pipe".
01 buf pic x(ConstBufLen) value spaces.
01 bufLen int value ConstBufLen.
01 offset int value 0.
01 i pic 999 value 0.
78 iMax value 5.
PROCEDURE DIVISION.
call "pipe" using fildes
returning ret
display "*--> Result call pipe: " ret
perform varying i from 1 by 1 until i = Imax
initialize buf
string bufConst delimited by space
i delimited by size
into buf
call "write" using by value fd1Write
by reference buf
by value bufLen
returning ret
display "*--> Result call write: " ret
if ret not = -1
display "*--> Result call write: " buf
end-if
end-perform
initialize buf
perform varying i from 1 by 1 until i = Imax
call "read" using by value fd0Read
by reference buf
by value buflen
by value offset
returning ret
display "*--> Result call read: " ret
if ret not = -1
display "*--> Result call read: " offset "/" buf
add ret to offset
end-if
end-perform
call "close" using by value fd0Read
returning ret
display "*--> Result call close: " ret
call "close" using by value fd1Write
returning ret
display "*--> Result call close: " ret
pipeCob.log = Trace of the execution of the code:
*--> Result call pipe: 0000000000
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe001
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe002
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe003
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe004
*--> Result call read: 0000000100
*--> Result call read: 0000000000/I-O_on_pipe001
*--> Result call read: 0000000100
*--> Result call read: 0000000100/I-O_on_pipe002
*--> Result call read: 0000000100
*--> Result call read: 0000000200/I-O_on_pipe003
*--> Result call read: 0000000100
*--> Result call read: 0000000300/I-O_on_pipe004
*--> Result call close: 0000000000
*--> Result call close: 0000000000
II) ==================
C Creates pipe & call cobol which writes in pipe & C read content of the pipe filled by COBOL
cob -x PipeCob.c CobolWrtPipe.cbl
Pipecob.c
#include <unistd.h>
#include <stdio.h>
#define MSGSIZE 100
char *msg1 = "hello #1";
char *msg2 = "hello #2";
char *msg3 = "hello #3";
main()
{ char inbuf[MSGSIZE];
int p[2], j, k;
/* open pipe */
if(pipe(p) == -1)
{ perror("pipe call error");
exit(1);
}
/* write down pipe */
write(p[1], msg1, MSGSIZE);
write(p[1], msg2, MSGSIZE);
write(p[1], msg3, MSGSIZE);
/* read pipe */
for(j=0; j<3; j )
{ read(p[0], inbuf, MSGSIZE);
printf("%s\\n", inbuf);
}
k = CobolWrtPipe(&p);
k--;
for(j=0; j<k; j )
{ read(p[0], inbuf, MSGSIZE);
printf("%s\\n", inbuf);
}
exit(0);
}
CobolWrtPipe.cbl
WORKING-STORAGE SECTION.
01 int pic s9(9) comp-5 is typedef.
01 ret int.
01 O-NODELAY int value 0.
78 ConstBufLen value 100.
78 bufConst value "I-O_on_pipe".
01 buf pic x(ConstBufLen) value spaces.
01 bufLen int value ConstBufLen.
01 offset int value 0.
01 i pic 999 value 0.
78 iMax value 5.
linkage section.
01 fildes.
02 fd0Read int.
02 fd1Write int.
PROCEDURE DIVISION using by reference fildes.
perform varying i from 1 by 1 until i = Imax
initialize buf
string bufConst delimited by space
i delimited by size
into buf
move low-value to buf(buflen : 1)
call "write" using by value fd1Write
by reference buf
by value bufLen
returning ret
display "*--> Result call write: " ret
if ret not = -1
display "*--> Result call write: " buf
end-if
end-perform
exit program returning Imax.
CobolWrtPipe.log
See below that COBOL has written in the pipe and C has read the pipe
hello #1 Begin C printf
hello #2
hello #3 End C printf
*--> Result call write: 0000000100 Begin COBOL DISPLAY
*--> Result call write: I-O_on_pipe001
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe002
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe003
*--> Result call write: 0000000100
*--> Result call write: I-O_on_pipe004 End COBOL DISPLAY
I-O_on_pipe001 Begin C printf
I-O_on_pipe002
I-O_on_pipe003
I-O_on_pipe004 End C printf
