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Programming
Communication between a java and c++ program
Post 10379 by rwb1959 on Tuesday 13th of November 2001 12:26:54 PM
11-13-2001
From your question, I assume you have 2
separate programs (1 java and 1 c++) and have
the source code for these programs. I also
assume that each of these programs reads stdin
for it's data and writes data to stdout.
I also assume that these programs have no
relationship to each other meaning that one
program does not start the other as a child.
If you want to use pipes, you may want to
consider FIFO devices (sometimes referred to
as a "named" pipe). You can create FIFO's
using the "mknode" command. If you want you
programs to utilize stdin and stdout, for example:
myjavaprog < /dev/myfifo1 > /dev/myfifo2 &
myc++prog < /dev/myfifo2 > /dev/myfifo1
then your code should first close all open
file descriptors and open /dev/myfifo1 and
/dev/myfifo2 for reading or writing as
appropriate. Also, you should open a file
for error output as well. Once you've done this,
the programs should work as if stdin and stdout
have been redirected. The main caveat here is that
you can expierence deadlock if your programs
block on reading or writing as reading and empty
pipe will wait forever and writing a full pipe
will block forever unless you set up your
connections as non-blocking. There are actually
a number of ways to deal with this but it does
require some forthought.
I hope this helps a bit.
separate programs (1 java and 1 c++) and have
the source code for these programs. I also
assume that each of these programs reads stdin
for it's data and writes data to stdout.
I also assume that these programs have no
relationship to each other meaning that one
program does not start the other as a child.
If you want to use pipes, you may want to
consider FIFO devices (sometimes referred to
as a "named" pipe). You can create FIFO's
using the "mknode" command. If you want you
programs to utilize stdin and stdout, for example:
myjavaprog < /dev/myfifo1 > /dev/myfifo2 &
myc++prog < /dev/myfifo2 > /dev/myfifo1
then your code should first close all open
file descriptors and open /dev/myfifo1 and
/dev/myfifo2 for reading or writing as
appropriate. Also, you should open a file
for error output as well. Once you've done this,
the programs should work as if stdin and stdout
have been redirected. The main caveat here is that
you can expierence deadlock if your programs
block on reading or writing as reading and empty
pipe will wait forever and writing a full pipe
will block forever unless you set up your
connections as non-blocking. There are actually
a number of ways to deal with this but it does
require some forthought.
I hope this helps a bit.
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LEARN ABOUT DEBIAN
fifo
FIFO(7) Linux Programmer's Manual FIFO(7) NAME
fifo - first-in first-out special file, named pipe DESCRIPTION
A FIFO special file (a named pipe) is similar to a pipe, except that it is accessed as part of the file system. It can be opened by multi- ple processes for reading or writing. When processes are exchanging data via the FIFO, the kernel passes all data internally without writ- ing it to the file system. Thus, the FIFO special file has no contents on the file system; the file system entry merely serves as a refer- ence point so that processes can access the pipe using a name in the file system. The kernel maintains exactly one pipe object for each FIFO special file that is opened by at least one process. The FIFO must be opened on both ends (reading and writing) before data can be passed. Normally, opening the FIFO blocks until the other end is opened also. A process can open a FIFO in nonblocking mode. In this case, opening for read only will succeed even if no-one has opened on the write side yet, opening for write only will fail with ENXIO (no such device or address) unless the other end has already been opened. Under Linux, opening a FIFO for read and write will succeed both in blocking and nonblocking mode. POSIX leaves this behavior undefined. This can be used to open a FIFO for writing while there are no readers available. A process that uses both ends of the connection in order to communicate with itself should be very careful to avoid deadlocks. NOTES
When a process tries to write to a FIFO that is not opened for read on the other side, the process is sent a SIGPIPE signal. FIFO special files can be created by mkfifo(3), and are indicated by ls -l with the file type 'p'. SEE ALSO
mkfifo(1), open(2), pipe(2), sigaction(2), signal(2), socketpair(2), mkfifo(3), pipe(7) COLOPHON
This page is part of release 3.44 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-12-03 FIFO(7)