5.18 POSIX 消息队列（上）：API编程实例

1、实验代码
mq_demo.c

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <mqueue.h>#define handle_error(msg) \do{
      perror(msg);exit(EXIT_FAILURE);}while(0)int main (void)
{
    mqd_t mq_id;if ((mq_id = mq_open("/posix_msg_queue", O_RDWR | O_CREAT, 0644, NULL)) == -1)handle_error("mq_open");struct mq_attr mq_attribute;if (mq_getattr (mq_id, &mq_attribute) == -1)handle_error("mq_getattr");printf ("mq_flags: %ld\n", mq_attribute.mq_flags);printf ("mq_maxmsg: %ld\n", mq_attribute.mq_maxmsg);printf ("mq_msgsize: %ld\n", mq_attribute.mq_msgsize);printf ("mq_curmsgs: %ld\n", mq_attribute.mq_curmsgs);int ret_from_fork;ret_from_fork = fork ();if (ret_from_fork == 0) // child process{
    char msg_buf[mq_attribute.mq_msgsize];memset (msg_buf, 0, mq_attribute.mq_msgsize);int count = 0;while (1){
    if (mq_receive (mq_id, msg_buf, mq_attribute.mq_msgsize, NULL) == -1)handle_error("mq_receive");printf ("child process received msg: %s\n", msg_buf);sleep (1);if (++count % 10 == 0)break;}}else if (ret_from_fork > 0) //parent process{
    int count = 0;while (1){
    if (mq_send (mq_id, "hello world", sizeof ("hello world"), 1) == -1)handle_error("mq_send");printf ("parent process: send msg to mqueue success\n");sleep (1);if (++count % 10 == 0)break;}}elsehandle_error("fork");mq_close (mq_id);sleep (5);if (mq_unlink ("/posix_msg_queue") == -1)handle_error("mq_unlink");return 0;
}

2、执行结果