UNIX IPC: POSIX 消息队列 与 信号

#include <stdio.h>
#include <stdlib.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <mqueue.h>
#include <signal.h>
#include <pthread.h>


mqd_t queue;
void* buff;
struct mq_attr attr;
struct sigevent sigev;

static void sig_user1(int signo) {
    printf("current pid:%d, threadid:%u\n", getpid(), pthread_self());
    int n, prio;
    /*     signal will be unregistered from previous registered message queue 
        when first message arrived.
        So register signal again if we want trigger the signal handler again */
    mq_notify(queue, &sigev);
    
    /* read msg */
    int res = mq_receive(queue, buff, attr.mq_msgsize, &prio);
    if (res < 0) {
        perror("receive msg fail");
        exit(-1);
    }
    printf("prio: %d, msg: %s\n", prio, (char*)buff);
    return;
}

int main(int argc, char** argv) {
    char* name = "/testmq";
    if (argc > 0) {
        name = argv[1];
    }

    queue = mq_open(name, O_RDONLY);

    if (queue < 0) {
        perror("open message queue fail");
        return -1;
    }

    int res = mq_getattr(queue, &attr);
    if (res != 0) {
        perror("get message queue fail");
        return -1;
    }

    buff = malloc(attr.mq_msgsize);

    signal(SIGUSR1, sig_user1);

    sigev.sigev_notify = SIGEV_SIGNAL;
    sigev.sigev_signo = SIGUSR1;

    mq_notify(queue, &sigev);

    printf("[%d.%d] start to waiting\n", getpid(), pthread_self());
    for (;;) {
        pause();
    }

    return 0;
}

hgf@ubuntu:~/ipc$ ./mqnotify /haha
[25328.1410565952] start to waiting
current pid:25328, threadid:1410565952