Share data between two indexpendent processes in C

Question

How do I share data (struct) between two independent(no fork) processes. What I want to do is basically something like this:

process1:

Server(PID-399341): Waiting for input....

then in another terminal

process2:

Enter server process:

399341

Enter a string:

Hello

finally

process1:

"Hello" has been entered. 

System is QNX/POSIX. What are my options to do this?

Thanks!

Answer 1

It can be easily achieved by using named pipe (FIFO). Just choose the name of the FIFO same as your PID. Here's a working code for server and client.

server.c

    int fd;
    char buf[10], rdbuf[50];

    sprintf(buf,"%d",getpid());

    if(mkfifo(buf,0660) == -1)
            perror("mkfifo");

    printf("Server(PID-%d): Waiting for input..\n",getpid());

    fd = open(buf,O_RDONLY);

    read(fd, rdbuf, 50);

    printf("%s has been entered\n",rdbuf);

    close(fd);

    return 0;

client.c

    int fd;
    char wrbuf[50], buf[10];

    printf("Enter server process: ");
    scanf("%s",buf);
    getchar();

    fd = open(buf,O_WRONLY);

    printf("Enter message\n");

    gets(wrbuf);

    write(fd, wrbuf, strlen(wrbuf)+1);

I think same can be done with message queue and shared mem segment by making the key value same as PID. But I am not sure.