linux作業系統訊息佇列

所謂訊息佇列就是指一個訊息鏈表。
int msgget(key_t, int flag)：建立和開啟隊列
int msgsnd(int msqid, struct msgbuf *msgp, size_t msgsz, int flag):發送訊息，msgid是訊息佇列的id，msgp是訊息內容所在的緩衝區，msgsz是訊息的大小，msgflg是標誌。

int msgrcv(int msqid, struct msgbuf *msgp, size_t msgsz, long msgtyp, int flag):接受訊息，msgtyp是期望接收的訊息類型。

msgqueue.c檔案內容如下；

#include<sys/types.h>#include<sys/ipc.h>#include<stdio.h>#include<stdlib.h>#include<unistd.h>#include<string.h>#include<pthread.h> // 增加線程支援#define BUFSZ 512struct message{    long msg_type;    char msg_text[BUFSZ];};#define MSG_SIZE sizeof(struct message)char app_exit = 0;void *thread_funtion(void *parg);int main(){    int qid;    key_t key;    int len;    int res;    pthread_t a_thread;    struct message msg;    if((key = ftok(".",'a')) == -1){ // ftok 獲得一個key        perror("ftok");        exit(1);    }    if((qid = msgget(key,IPC_CREAT|0666)) == -1){ // 建立一個訊息佇列        perror("msgget");        exit(1);    }    printf("opened queue %d\n",qid);    puts("Please enter the message to queue:");    if((fgets(msg.msg_text,BUFSZ,stdin)) == NULL){ // 從標準輸入獲得buffer        puts("no message");        exit(1);    }        msg.msg_type = getpid();    len = strlen(msg.msg_text) + sizeof(msg.msg_type);    if((msgsnd(qid,&msg,len,0)) < 0){ // 發送訊息        perror("message posted");        exit(1);    }    /*    memset(&msg,0,sizeof(msg)); // 清除記憶體為0    if(msgrcv(qid,&msg,len,0) < 0){ // 接收訊息        perror("message recv");        exit(1);    }    printf("message is:%s\n",(&msg)->msg_text);    if((msgctl(qid,IPC_RMID,NULL))<0){        perror("msgctl");        exit(1);    }*/    res = pthread_create(&a_thread,NULL,thread_funtion,(void *)&qid);        printf("The msgrcv thread is create sucess!\n");while((app_exit =  getchar()) != 'e'){sleep(50);}        printf("exit main funtion!\n");    exit(0);}void *thread_funtion(void *parg){    struct message msg;    int qid;        qid = *((int *)parg);    memset(&msg,0,MSG_SIZE);    while(app_exit != 'e'){        if(msgrcv(qid,&msg,MSG_SIZE) < 0){            sleep(50);            continue;        }        printf("message is:%s\n",(&msg)->msg_text);        if(msgctl(qid,IPC_RMID,NULL) < 0){            perror("msgctl");        }        sleep(50);    }}

Makefile檔案類型如下；

all:msgqueue# which compilerCC = gcc# Where are include file keptINCLUDE = .# Where to installINSTDIR = /usr/local/bin# Options for developmentCFLAGS = -g -Wall -ansimsgqueue:msgqueue.o$(CC) -D_REENTRANT -o msgqueue msgqueue.o -lpthreadmsgqueue.o:msgqueue.c#$(CC) -I$(INCLUDE) $(CFLAGS) -c msgqueue.c#$(CC) -D_REENTRANT -c msgqueue.c -lpthread$(CC) -c msgqueue.cclean:-rm msgqueue.o msgqueueinstall:msgqueue@if [-d $(INSTDIR) ];\        then \        cp msgqueue $(INSTDIR);\        chmod a+x $(INSTDIR)/msgqueue;\        chmod og-w $(INSTDIR)/msgqueue;\        echo "Install in $(INSTDIR)";\    else \       echo "Sorry,$(INSTDIR) does not exist";\    fi