实验五进程间通信

实验五进程间通信UNIX/LINUX系统的进程间通信机构（IPC）允许在任意进程间大批量地交换数据。

本实验的目的是了解和熟悉LINUX支持的信号机制、管道机制、消息队列通信机制及共享存储区机制。

信号机制实验（一）【实验目的】1．了解什么是信号。

2．熟悉LINUX系统中进程之间软中断通信的基本原理。

【实验原理】利用signal来实现发送信号和接受信号的原理【实验内容】1．编写一段程序，使用系统调用fork( )创建两个子进程，再用系统调用signal( )让父进程捕捉键盘上来的中断信号（即按ctrl+c键），当捕捉到中断信号后，父进程用系统调用kill( )向两个子进程发出信号，子进程捕捉到父进程发来的信号后，分别输出下列信息后终止：Child process 1 is killed by parent!Child process 2 is killed by parent!父进程等待两个子进程终止后，输出以下信息后终止：Parent process is killed!<参考程序># include<># include<># include<>int wait_mark;void waiting(),sto p();void main(){ int p1, p2;signal(SIGINT,stop);while((p1=fork())==-1);if(p1>0) /*在父进程中*/{ ①while((p2=fork())= =-1);If(p2>0) /*在父进程中*/{ ②wait_mark=1;waiting(0);kill(p1,10);kill(p2,12);wait( );wait( );printf(“parent process is killed!\n”);exit(0);}else /*在子进程2中*/{wait_mark=1;signal(12,stop);waiting();lockf(1,1,0);printf(“child process 2 is killed by parent!\n”);lockf(1,0,0);exit(0);}}else /*在子进程1中*/{wait_mark=1;signal(10,stop);waiting();lockf(1,1,0);printf(“child process 1 is killed by parent!\n”);lockf(1,0,0);exit(0);}}void waiting(){while(wait_mark!=0);}void stop(){wait_mark=0;}实验要求：⑴运行程序并分析结果。

⑵如果把signal(SIGINT,stop)放在①号和②号位置，结果会怎样并分析原因。

⑶该程序段前面部分用了两个wait(0),为什么？⑷该程序段中每个进程退出时都用了语句exit(0),为什么？信号机制实验（二）【实验目的】学习signal的函数的使用【实验原理】利用signal的函数的机制来实习我们发送截获信号的功能【实验内容】修改上面的程序，增加语句signal(SIGINT,SIG_IGN)和语句signal(SIGQUIT,SIG_IGN)，再观察程序执行时屏幕上出现的现象，并分析其原因。

<参考程序># include<># include<># include<>int pid1, pid2;int EndFlag=0;pf1=0;pf2=0;void IntDelete(){kill(pid1,10);kill(pid2,12);EndFlag=1;}void Int1(){printf(“child process 1 is killed by parent !\n”);exit(0);}void Int2(){printf(“child process 2 is killed by parent !\n”);exit(0);}main(){int exitcode;signal(SIGINT,SIG_IGN);signal(SIGQUIT,SIG_IGN);while((pid1=fork())==-1);if(pid1==0){signal(SIGUSR1,Int1);signal(SIGINT,SIG_IGN);pause();exit(0);}elsewhile((pid2=fork())= =-1);if(pid2==0){signal(SIGUSR2,Int2);signal(SIGINT,SIG_IGN);pause();exit(0);}else{signal(SIGINT,IntDelete);waitpid(-1,&exitcode,0); /*等待任何子进程中断或结束*/printf(“parent process is killed \n”);exit(0);}}}实验要求：运行程序并分析结果。

⑶司机售票员问题（选做题）编程用fork()创建一个子进程代表售票员，司机在父进程中，再用系统调用signal()让父进程（司机）捕捉来自子进程（售票员）发出的中断信号，让子进程（售票员）捕捉来自（司机）发出的中断信号，以实现进程间的同步运行。

管道通信实验（一）【实验目的】1、了解什么是管道2、熟悉UNIX/LINUX支持的管道通信方式【实验内容】编写程序实现进程的管道通信。

用系统调用pipe( )建立一管道，二个子进程P1和P2分别向管道各写一句话：Child 1 is sending a message!Child 2 is sending a message!父进程从管道中读出二个来自子进程的信息并显示（要求先接收P1，后P2）。

参考程序#include <>#include <>#include <>main( ){int fd[2];char outpipe[100],inpipe[100];pipe(fd); /*创建一个管道*/while ((pid1=fork( ))= =-1);if(pid1= =0){lockf(fd[1],1,0);sprintf(outpipe,"child 1 process is sending message!");/*把串放入数组outpipe中*/write(fd[1],outpipe,50); /*向管道写长为50字节的串*/sleep(5); /*自我阻塞5秒*/lockf(fd[1],0,0);exit(0);}else{while((pid2=fork( ))= =-1);if(pid2= =0){ lockf(fd[1],1,0); /*互斥*/sprintf(outpipe,"child 2 process is sending message!");write(fd[1],outpipe,50);sleep(5);lockf(fd[1],0,0);exit(0);}else{ wait(0); /*同步*/read(fd[0],inpipe,50); /*从管道中读长为50字节的串*/printf("%s/n",inpipe);wait(0);read(fd[0],inpipe,50);printf("%s/n",inpipe);exit(0);}}}五、运行结果延迟5秒后显示child 1 process is sending message!再延迟5秒child 2 process is sending message!管道通信实验（二）【实验目的】1、掌握有名管道的创建和读写方式2、熟悉UNIX/LINUX支持的有名管道通信方式【实验内容】1.创建有名管道2.本进程执行循环等待数据被写入到管道中并读有名管道3.打开有名管道并写数据到名管道参考代码：.);if ((fd = open(argv[1], O_RDONLY)) < 0){fprintf(stderr, "open fifo %s for reading failed: %s\n", argv[1], strerror(errno));exit(1);}fprintf(stdout, "open fifo %s for reading successed.\n", argv[0]);char buffer[BUFFER_SIZE];ssize_t n;while (1){again:n");break;}else{buffer[n] = '\0';fprintf(stdout, "read %d bytes from fifo: %s\n", n, buffer);}}return 0;}.);if ((fd = open(argv[1], O_WRONLY)) < 0){fprintf(stderr, "open fifo %s for writting failed: %s\n", argv[1], strerror(errno));exit(1);}fprintf(stdout, "open fifo %s for writting successed.\n", argv[0]);char buffer[BUFFER_SIZE];ssize_t n;n");}else{fprintf(stderr, "Error: open file failed: (errno = %d)%s\n", errno, strerror(errno));}exit(1);}off_t offset;offset = 1024;On error, the value MAP_FAILED (that is, (void*) -1) is returned, and errno is set appropriately. On success, munmap returns 0, on failure -1, and errno is set (probably to EINVAL).*//*PROT_EXEC Pages may be executed.PROT_READ Pages may be read.PROT_WRITE Pages may be written.PROT_NONE Pages may not be accessed.*/void *p;;On error, the value MAP_FAILED (that is, (void*) -1) is returned, and errno is set appropriately. On success, munmap returns 0, on failure -1, and errno is set (probably to EINVAL).*//*PROT_EXEC Pages may be executed.PROT_READ Pages may be read.PROT_WRITE Pages may be written.PROT_NONE Pages may not be accessed.*/void *p;1L3L4L4L2L3L4L3L1L3L4L2LserverReceive client1 message: i 'am client AReceive client2 message: ok! I have recieved your msg,I'm client B Receive client1 message: x[root@localhost root]#客户端A的运行结果如下：[root@localhost root]# ./client1input the msg to client2:i 'am client AReceive from client2, message: ok! I have recieved your msg,I'm client B input the msg to client2:xclient1 will quit![root@localhost root]#客户端B的运行结果如下：[root@localhost root]# ./client2Receive from client1, message: i 'am client Ainput the msg to client1: ok! I have recieved your msg,I'm client Bclient2 will quit![root@localhost root]#。