POSIX发送接收消息

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#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：

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

　　

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#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：

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