Linux进程间通信IPC学习笔记之消息队列(Posix)
基础知识:
消息队列可认为是一个消息链表,有足够写权限的线程可往队列中放置消息,有足够读权限的线程可以从队列中取走消息。在某个进程往一人队列写入消息之前,并不需要另外某个进程在该队列上等待消息的到达。其特性为:
1)具有内核的持续性:即当一个进程往某一个队列写入一些消息后终止,而另一个进程可以在以后的某个时刻取出该消息;
2)
#include <mqueue.h> mqd_t mq_open(const char *name, int oflag, ... /* mode_t mode,struct mq_attr *attr */); 返回:若成功则返回消息队列描述符,否则返回-1 #include <mqueue.h> int mq_close(mqd_t mqdes); 返回:若成功返回0,否则返回-1 #include <mqueue.h> int mq_unlink(const char *name); 返回:若成功返回0,否则返回-1 #include <mqueue.h> int mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio); 返回:若成功返回0,否则返回-1
ssize_t mq_receive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned *msg_prio); 返回:若成功返回消息中字节数,否则返回-1 #include <mqueue.h> int mq_getattr(mqd_t mqdes, struct mq_attr *mqstat); int mq_setattr(mqd_t mqdes, const struct mq_attr *restrict mqstat, struct mq_attr *restrict omqstat); 返回:若成功返回0,否则返回-1 #include <mqueue.h> #include <time.h> ssize_t mq_timedreceive(mqd_t mqdes, char *restrict msg_ptr, size_t msg_len, unsigned *restrict msg_prio, const struct timespec *restrict abs_timeout); int mq_timedsend(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio, const struct timespec *abs_timeout); #include <mqueue.h> int mq_notify(mqd_t mqdes, const struct sigevent *notification);
返回:若成功返回0,否则返回-1
![](https://images.cnblogs.com/OutliningIndicators/ContractedBlock.gif)
struct mq_attr{ long mq_flags; //message queue flags long mq_maxmsg; //maximum number of messages long mq_msgsize; //maximum message size long mq_curmsgs; //number of messages currently queued }; struct sigevent { int sigev_notify; //notification type int sigev_signo; //signal number union sigval sigev_value; //signal value void (*sigev_notify_function) (union sigval); //notification function pthread_attr_t *sigev_notify_attributes; //notification attributes } union sigval { int sival_int; //integer value void *sival_ptr; //pointer value }
测试代码:
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