Message Queue

[tiagokos]

Opa, tenho uma dúvida quanto ao Message Queue, como faço para me comunicar com os processos filhos em um mesmo código?

Tenho que abrir as MQ denovo a cada processo?

Segue meu email, em ingles, já que perguntei em mais de um forum.

Obrigadão!!!

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Hey all,

I'm having some troubles using Message Queue, could you please help me?

I have to send a Message from the root process to it's children after inserting a char (if char == number, send to child 1, if char == letter, send to child 2).

I'm not getting the buffer back in the children process, what am i doing wrong?

#include <sys/shm.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <errno.h>
#include <mqueue.h>

int main() {
    int pid1;
    int pid2;
    mqd_t mq;
    struct mq_attr attr;
    char buffer;

    attr.mq_flags = 0;
    attr.mq_maxmsg = 1;
    attr.mq_msgsize = 1024;
    attr.mq_curmsgs = 0;

    pid1 = fork();
    if (pid1 == 0) {
        mq = mq_open("/test_queue", O_CREAT | O_RDONLY, 0644, &attr);
        while(mq_receive(mq, &buffer, 1024, NULL) != 1024);
        if ((char)*buffer >= 'A' && (char)*buffer <= 'z') {
            printf("1 - %c\n", toupper((char)*buffer));
        }             
    }
    else if (pid1 > 0) {
        pid2 = fork();
        if (pid2 == 0 && pid1 > 0) {
                mq = mq_open("/test_queue", O_CREAT | O_RDONLY, 0644, &attr);
                while(mq_receive(mq, &buffer, 1024, NULL) != 1024);
            if(isdigit((char)*buffer)) {
                printf("2 - %c\n", (char)*buffer);
            }
        }
        else if (pid2 > 0) {
            
            mq = mq_open("/test_queue", O_WRONLY);

            printf("Inform a char:\n");
            scanf("%c", &buffer);
                    
            
            if (isdigit((char)*buffer)) {
                                  //SEND TO CHILD 1
                                  mq_send(mq, &buffer, 1024, 0);    
            }
            else if ((char)*buffer >= 'A' && (char)*buffer <= 'z') {
                                 //SEND TO CHILD 2
                                 mq_send(mq, &buffer, 1024, 0);    
            } 
            else {
                printf("Ignored.\n");
                exit(0);
            }
        }
        else {
            printf("Err.\n");
        }
    }
    else {
        printf("Err.\n");
    }
    
    wait();
    mq_close(mq);
    mq_unlink("/test_queue");
    return 0;
}

Thanks very much,

Tiago