POSIX消息队列

#include <mqueue.h> 
mqd_t mq_open(const char *name, int oflag, /* mode_t mode, struct mq_attr *attr */); //成功返回消息队列描述符，失败返回-1 


mqd_t mq_close(mqd_t mqdes); 

mqd_t mq_unlink(const char *name); //成功返回0，失败返回-1

#include <bits/mqueue.h>
typedef int mqd_t;

#include <mqueue.h> 
mqd_t mq_getattr(mqd_t mqdes, struct mq_attr *attr); 
mqd_t mq_setattr(mqd_t mqdes, struct mq_attr *newattr, struct mq_attr *oldattr); //成功返回0，失败返回-1

#include <bits/mqueue.h> 
struct mq_attr
 {
     long int mq_flags; /* Message queue flags. */消息队列的标志：0或O_NONBLOCK,用来表示是否阻塞 0 O_NONBLOCK
     long int mq_maxmsg; /* Maximum number of messages. */消息队列的最大消息数
     long int mq_msgsize; /* Maximum message size. */消息队列中每个消息的最大字节数
     long int mq_curmsgs; /* Number of messages currently queued. */ 消息队列中当前的消息数目
　　　long int __pad[4];
 };

#include <mqueue.h>
mqd_t mq_send(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio); //成功返回0，出错返回-1 
mqd_t mq_receive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned *msg_prio); //成功返回接收到消息的字节数，出错返回-1


#ifdef __USE_XOPEN2K 
mqd_t mq_timedsend(mqd_t mqdes, const char *msg_ptr, size_t msg_len, unsigned msg_prio, const struct timespec *abs_timeout);
mqd_t mq_timedreceive(mqd_t mqdes, char *msg_ptr, size_t msg_len, unsigned *msg_prio, const struct timespec *abs_timeout); 
#endif

//mqsend,c
#include "unpipc.h"
#include <mqueue.h>

int main()
{
    printf("请输入消息队列的名字:");
    char name[MAXLINE];
    fgets(name,MAXLINE,stdin);
    int len=strlen(name);
    if(name[len-1]==‘\n‘)
        --len;

    int flags=O_RDWR|O_CREAT|O_EXCL;
    mqd_t mqd=mq_open(name,flags,FILE_MODE,NULL);
    if(mqd<0)
        if(errno==EEXIST)
        {
            mq_unlink(name);
            mqd=mq_open(name,O_RDWR|O_CREAT,FILE_MODE,NULL);
        }
        else
        {
            printf("open message queue error...\n");
            return -1;
        }

    struct mq_attr attr;
    mq_getattr(mqd,&attr);
    char msg[MAXLINE];

    int i;
    for(i=0;i<6;++i)
    {
        printf("请输入第 %d 个消息:",i+1);
        scanf("%s",msg);
        printf("请输入第 %d 个消息的优先级:",i+1);
        int prio;
        scanf("%d",&prio);

        if(mq_send(mqd,msg,sizeof(msg),prio)<0)
            printf("send message: %d faild.error info: %s\n",i,strerror(errno));
        
        printf("send message: %d success.\n",i+1);

    }
    exit(0);
}

//mqreceive.c
#include "unpipc.h"
#include <mqueue.h>

int main()
{
    char name[MAXLINE];
    printf("请输入接受消息的消息队列的名字:");
    fgets(name,MAXLINE,stdin);
    int len=strlen(name);
    if(name[len-1]==‘\n‘)
        --len;

    mqd_t mqd=mq_open(name,O_RDONLY);

    struct mq_attr attr;
    mq_getattr(mqd,&attr);
    char *buffer=(char *)malloc(sizeof(char)*attr.mq_msgsize);

    int i;
    for(int i=0;i<6;++i)
    {
        int prio;
        if(mq_receive(mqd,buffer,attr.mq_msgsize,&prio)<0)
        {
            printf("receive message failed. error info: %s\n",strerror(errno));
            continue;
        }
        printf("receive message %d: %s, prio is: %d\n",i+1,buffer,prio);
    }
    mq_close(mqd);
    exit(0);
}

mqd_t mq_notify(mqd_t mqdes, const struct sigevent *notification);

struct sigevent
{
    int sigev_notify; //notification type SIGEV_{NONE,SIGNAL,THREAD}
    int sigev_signo; //signal number if SIGEV_SIGNAL
    union sigval   sigev_value; //signal value
    void (*sigev_notify_function)(union sigval);//passed to signal handeler or thread following two if SIGEV_THREAD
    pthread_attr_t *sigev_notify_attributes;
}

union sigval
{
    int sival_int; //integer value
    void *sival_ptr; //pointer value
}

//文件:/usr/include/asm-generic/siginfo.h 
typedef struct sigevent 
{
    sigval_t sigev_value;//notification type
    int sigev_signo;//signal number
    int sigev_notify;
　　
    union 
    {
        int _pad[SIGEV_PAD_SIZE];
        int _tid;

        struct 
        {
            void (*_function)(sigval_t);
            void *_attribute;    /* really pthread_attr_t */
        } _sigev_thread;
    } _sigev_un;
} sigevent_t;