Unix-进程间通信

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1、有名管道间通信

read进程代码：

#include<sys/types.h>#include<sys/stat.h>#include<errno.h>#include<fcntl.h>#include<stdio.h>#include<stdlib.h>#include<string.h>#define FIFO "/tmp/myfifo"int main(int argc , char** argv){char buf_r[100];int fd;int nread;if((mkfifo(FIFO,O_CREAT | O_EXCL)<0)&& (errno!=EEXIST))printf("cannot create fifo\n");printf("prapare for reading bytes \n");memset(buf_r,0,sizeof(buf_r));fd = open(FIFO,O_RDONLY | O_NONBLOCK,0);if(fd == -1){perror("open");exit(1);}while(1){memset(buf_r,0,sizeof(buf_r));if((nread = read(fd,buf_r,100)==-1)){if(errno== EAGAIN)printf("no data \n");}elseprintf("read from FIFO %s \n",buf_r);sleep(1);}pause();}

write 代码：

#include<sys/types.h>#include<sys/stat.h>#include<errno.h>#include<fcntl.h>#include<stdio.h>#include<stdlib.h>#include<string.h>#define FIFO_SERVER "/tmp/myfifo"int main(int argc ,char** argv){int fd;char w_buf[100];int nwrite;fd = open(FIFO_SERVER,O_WRONLY | O_NONBLOCK,0);if(argc == 1){exit(-1);}strcpy(w_buf,argv[1]);if((nwrite = write(fd,w_buf,100))==-1){if(errno == EAGAIN)printf("the fifo is not read\n");}elseprintf("write %s to the fifo\n",w_buf);return 0;}

2、信号量通信

#include<signal.h>#include<stdio.h>#include<stdlib.h>void my_func(int sign_no){if(sign_no == SIGINT)printf("I have get SIGINT\n");else if(sign_no == SIGQUIT)printf("I have get SIGQUIT\n");}void main(){printf("Waiting for signal SIGINT or SIGQUIT\n");signal(SIGINT,my_func);signal(SIGQUIT,my_func);pause();exit(0);}

mysignal.c

运行该文件，在另一个终端中执行

kill -s SIGQUIT 'pid'

这里的pid为mysignal的进程号

通过kill向进程mysignal发送信号。mysignal得到信号后，打印相应的信息。

3、共享内存通信：

共享内存是被多个进程共享的一部分物理内存。共享内存是进程间共享数据的一种最快的方法，一个进程向共享内存区域写入了数据，共享这个区域的所有进程就可以立刻看到其中的内容

#include<stdlib.h>#include<stdio.h>#include<string.h>#include<errno.h>#include<unistd.h>#include<sys/stat.h>#include<sys/types.h>#include<sys/ipc.h>#include<sys/shm.h>int main(int argc , char**argv){int shmid;char *p_addr,*c_addr;if(argc != 2){fprintf(stderr,"Usage:%s \n \a",argv[0]);exit(1);}//创建共享内存对象if((shmid = shmget(IPC_PRIVATE,1024,IPC_CREAT)) == -1){fprintf("create Share Memory Error: %s\n",strerror(errno));exit(1);}//create Processif(0 !=fork())//father Process{       //把共享内存区对象映射到调用进程的地址空间p_addr = shmat(shmid,0,0);memset(p_addr,'\0',1024);strncpy(p_addr,argv[1],1024);wait(NULL);shmdt(p_addr);//断开共享内存连接shmctl(shmid,IPC_RMID,NULL);//IPC_RMID：删除这片共享内存exit(0);}else //child Process{<span style="white-space:pre"></span>sleep(1);c_addr = shmat(shmid,0,0);printf("Client get %s\n",c_addr);<span style="white-space:pre"></span>shmdt(c_addr);//断开共享内存连接exit(0);}}

4、消息队列

#include <sys/types.h>#include <sys/msg.h>#include <unistd.h>#include <string.h>#include <stdio.h>struct msg_buf{        int mtype;        char data[255];};int main(){        key_t key;        int msgid;        int ret;        struct msg_buf msgbuf;        key = ftok("/tmp/1",'a');//创建key        printf("key= [%x]\n",key);        msgid = msgget(key,IPC_CREAT|0666);//创建一个新队列或打开一个存在的队列        if(msgid==-1)        {                printf("create error \n");        }        msgbuf.mtype = 10;        strcpy(msgbuf.data,"test haha");        ret=msgsnd(msgid,&msgbuf,sizeof(msgbuf.data),IPC_NOWAIT);//数据放到消息队列中        if(ret==-1)        {                printf("send error\n");                return -1;        }        memset(&msgbuf,0,sizeof(msgbuf));        ret=msgrcv(msgid,&msgbuf,sizeof(msgbuf.data),10,IPC_NOWAIT);//从消息队列中接收数据        if(ret==-1)        {                printf("receive error \n");                return -1;        }        printf("receive : %s\n",msgbuf.data);        return 0;}

5、信号量

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