POSIX发送接收消息

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

int main(int argc, char **argv) {
	mqd_t mqd;
	void *ptr;
	size_t len, prio;

	if(argc!=4) {
		fprintf(stderr, "usage: ./a.out <name> <#bytes> <priority>\n");
		exit(-1);
	}

	len=atoi(argv[2]);
	prio=atoi(argv[3]);

	mqd=mq_open(argv[1], O_WRONLY);

	ptr=calloc(len, sizeof(char));

	mq_send(mqd, ptr, len, prio);

	exit(0);
}

往队列中增加消息运行示例：

$ ./mqsend /test 100 30
$ ./mqgetattr /test
max #msgs=10, max #bytes/msg=8192, #currently on queue=1

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

int main(int argc, char **argv) {
	int c, flags;
	mqd_t mqd;
	ssize_t n;
	unsigned int prio;
	void *buff;
	struct mq_attr attr;

	flags=O_RDONLY;
	while((c=getopt(argc, argv, "n"))!=-1) {
		switch(c) {
		case 'n':
			flags|=O_NONBLOCK;
			break;
		}
	}

	if(optind!=argc-1) {
		fprintf(stderr, "usage: ./a.out [-n] <name>\n");
		exit(-1);
	}

	mqd=mq_open(argv[optind], flags);
	mq_getattr(mqd, &attr);
	buff=malloc(attr.mq_msgsize);

	n=mq_receive(mqd, buff, attr.mq_msgsize, &prio);
	printf("read %ld bytes, priority=%u\n", (long)n, prio);

	exit(0);
}

从队列中读入消息：

$ ./mqreceive -n /test
read 100 bytes, priority=30
$ ./mqgetattr /test
max #msgs=10, max #bytes/msg=8192, #currently on queue=0