进程间通信

在linux中实现共享内存方式的进程间通信
上面代码都在
linux:Ubuntu12.04
gcc:4.6.3 上运行通过。

分别有两个程序运行read.c和write.c
write.c从终端输入到全局定义的结构体shm_t的buf[]数组中
read.c从buf[]中读取并输出、打印

下面为read.c文件

#include<stdio.h>#include<stdlib.h>#include<sys/types.h>#include<sys/ipc.h>#include<sys/shm.h>#include<errno.h>#include<unistd.h>#include<signal.h>//包含的头文件#include<string.h>//利用共享内存进行进程间的通信typedef struct{    pid_t pid;    char buf[100];//定义的结构体}shm_t;void fun(int signum){    //空操作}int main(int argc, const char *argv[]){    key_t key;    int shmid;    pid_t pid;    shm_t *p;//recive the signal from the write //then turn to pause()    signal(SIGUSR1,fun);//init the shmid memory    key = ftok(".",'a');//key_t ftok(const char *pathname, int proj_id)                           define the key value    if((shmid = shmget(key,100,0664 | IPC_CREAT | IPC_EXCL)) == -1){        if(errno == EEXIST){            shmid = shmget(key,100,0664); //int shmget(key_t key, size_t size, int shmflg);                                            //shmflag follows IPC_CREAT IPC_EXCL            p = (shm_t *)shmat(shmid,NULL,0);//有必要进行强转，在我运行时不强转会出问题            //the purpose of this step send             //the pid of process            pid = p->pid;            p->pid = getpid();//get the current pidnum            kill(pid,SIGUSR1);//send signal to write        }        else{            perror("shget");            exit(1);        }    }    //当shimd不存在，首次执行时    else{        p = (shm_t *)shmat(shmid,NULL,0);        p->pid = getpid();        pause();//wait for signal from write        pid = p->pid;//change the struct's pid number    }    while(1){    //程序阻塞在这里等待write发送信号        pause();        //when enter the quit,will quit from the progress        if(strncmp(p->buf,"quit",4) == 0){            break;//breakout the while(1)         }        printf("buf is %s",p->buf);        //send signal the write        kill(pid,SIGUSR1);    }//destroy the shmid     shmdt(p);    shmctl(shmid,IPC_RMID,NULL);    return 0;}

接下来是write.c文件，用于向共享内存进行写内容

**#include<>;;;has the same headfiles as read.c has**int main(int argc, const char *argv[]){    key_t key;    shm_t *p;    int shmid;    pid_t pid;    signal(SIGUSR1,fun);//same function as read do//init the     key = ftok(".",'a');    if((shmid = shmget(key,sizeof(shm_t),0664 | IPC_CREAT|IPC_EXCL)) == -1){        if(errno == EEXIST){            shmid = shmget(key,100,0664);            p = (shm_t *)shmat(shmid,NULL,0);            pid = p->pid;            p->pid = getpid();            kill(pid,SIGUSR1);        }        else{            perror("shmget");            exit(1);        }    }    else{        p = (shm_t *)shmat(shmid,NULL,0);        p->pid = getpid();        pause();        pid = p->pid;    }    while(1){        //read the charaters from terminal        fgets(p->buf,100,stdin);        kill(pid,SIGUSR1);//send the signal to read        if(strncmp(p->buf,"quit",4) == 0)            break;//breakout while()        pause();//wait the signal from read    }    return 0;}

进程间通信的方式有很多，管道：有名管道、无名管道 ，信号，共享内存，消息队列，信号灯等，还有套接字，会在网络编程里出现比较多。