linux 进程通信 C程序案例

编写C程序完成：父进程创建两个子进程，每个进程都在屏幕上显示自己的进程ID号，并在第1个子进程中加载执行一条外部命令。

#include 
#include 
#include 
#include 
#include 
#include int main(int argc, char const *argv[])
{pid_t c1 = fork();if(c1 == 0)          //child1{   printf("[%d] : child1\n", getpid());execl("/bin/sh", "sh", "-c", "date", (char *)0);}else if(c1 > 0)     //parent{   printf("[%d] : parent\n", getpid());pid_t c2 = fork();if(c2 == 0)     //child2{printf("[%d] : child2\n", getpid());}else if(c2 > 0)       //parent{   printf("[%d] : parent\n", getpid());int status;wait(&status);}}return 0;
}

编写C程序完成：父进程创建1个子进程，然后建立无名管道与子进程互相传递问候信息（父进程发出“hello！”，子进程发出“Hi!”），最后各自将接收到的信息输出到屏幕。

#include 
#include 
#include 
#include 
#include 
#include int main()
{char *parent_talk[] = {"hello",  NULL};char *child_talk[] = {"hi",  NULL};int fd1[2];int fd2[2];int res = pipe(fd1);if (res == -1){printf("create pipe error.\n");exit(1);}res = pipe(fd2);if (res == -1){printf("create pipe erroe.\n");exit(1);}pid_t pid;pid = fork();if (pid == 0) //子进程{close(fd1[1]); //子进程关闭fd1的写端，关闭fd2的读端close(fd2[0]);char buf[256];int i;char *talk = child_talk[i];while (talk != NULL){sleep(5);read(fd1[0], buf, 256);printf("父进程:>%s\n", buf);write(fd2[1], talk, strlen(talk) + 1);i++;talk = child_talk[i];}close(fd1[0]);close(fd2[1]);}else if (pid > 0){close(fd1[0]); //父进程关闭fd1的读端，关闭fd2的读端close(fd2[1]);char buf[256];int i = 0;char *talk = parent_talk[i];while (talk != NULL){write(fd1[1], talk, strlen(talk) + 1);read(fd2[0], buf, 256);printf("子进程:>%s\n", buf);i++;talk = parent_talk[i];}close(fd1[1]);close(fd2[0]);int status;wait(&status);}return 0;
}

理解创建进程的系统调用并分析fork()与vfork()异同。

#include 
#include 
#include 
#include 
#include 
int main(void)
{int data = 0;pid_t pid;int choose = 0;while ((choose = getchar()) != 'q'){switch (choose){case '1':pid = fork();// fork的返回值，大于0 的时候，代表是父进程。此时的返回值，刚好是子进程的pid号// fork的返回值，等于0 的时候，代表的是子进程。此时的子进程的pid号其实是复制了fork大于0 的返回值。if (pid < 0)printf("Error !\n");if (pid == 0) // 子进程执行后+1{data++;exit(0);}wait(NULL);if (pid > 0)printf("data is %d\n", data); // 子进程未执行 ,为 0break;case '2':pid = vfork(); //  vfork()：保证子进程先运行if (pid < 0)   // 出错perror("Error !\n");if (pid == 0) // 子进程执行后+1{data++;exit(0);}wait(NULL);if (pid > 0)printf("data is %d\n", data); // 由于vfork保证子进程先运行 所以为1break;default:break;}}return 0;
}

实现一个程序启动另一个程序后自身仍然在运行，即在子进程中加载执行其他程序而父进程等待子进程结束后才结束。

#include 
#include 
#include 
#include 
#include 
#include 
#include 
int main()
{/*接受键盘输入命令字符*/char buf[88];fgets(buf, 88, stdin);pid_t pid;pid = fork();/*创建子进程*/if (pid < 0)perror("创建子进程失败");else if (0 == pid){/*用exec()加载程序执行输入的命令*/execl("/bin/sh", "sh", "-c", buf, (char *)0);}else{/*等待子进程信息*/wait(NULL);/*继续父进程的执行*/printf("父进程执行成功");}
}

编写一段C语言程序使其完成：父子进程通过无名管道传递三条消息：

• 管道文件的测试程序开始
• 管道文件测试正在进行
• 管道通信测试结束

#include 
#include 
#include 
#include 
#include 
#include 
/*进程间通信（IPC机制)通信方式有： 管道 有名管道 消息队列 信号量  共享内存 套接字管道：是一种半双工的通信方式 只能在具有亲缘关系的进程间使用有名管道：也是半双工的通信方式，但是它允许无亲缘关系进程间的通信
*///实现父子进程之间相互发送消息
int main()
{char *parent_talk[] = {"管道文件的测试程序开始", "管道文件测试正在进行", "管道通信测试结束", NULL};char *child_talk[] = {"好的", "一切正常", "拜拜", NULL};int fd1[2];int fd2[2];int res = pipe(fd1);if (res == -1){printf("create pipe error.\n");exit(1);}res = pipe(fd2);if (res == -1){printf("create pipe erroe.\n");exit(1);}pid_t pid;pid = fork();if (pid == 0) //子进程{close(fd1[1]); //子进程关闭fd1的写端，关闭fd2的读端close(fd2[0]);char buf[256];int i;char *talk = child_talk[i];while (talk != NULL){sleep(5);read(fd1[0], buf, 256);printf("父进程:>%s\n", buf);write(fd2[1], talk, strlen(talk) + 1);i++;talk = child_talk[i];}close(fd1[0]);close(fd2[1]);}else if (pid > 0){close(fd1[0]); //父进程关闭fd1的读端，关闭fd2的读端close(fd2[1]);char buf[256];int i = 0;char *talk = parent_talk[i];while (talk != NULL){write(fd1[1], talk, strlen(talk) + 1);read(fd2[0], buf, 256);printf("子进程:>%s\n", buf);i++;talk = parent_talk[i];}close(fd1[1]);close(fd2[0]);int status;wait(&status);}return 0;
}

利用Linux/UNIX的软中断信号，编写一段C语言程序完成：显示数字1到100，在程序运行中如果捕获到一个SIGINT信号，则转去执行一段显示当前系统时间的程序。在编程中要考虑到信号被复位的情况，使程序能够实现多次被打断却多次的恢复执行。

#include 
#include 
#include 
#include 
#include 
void handler(int signo)
{signal(SIGINT, SIG_IGN);time_t timep;time(&timep);printf("now the time is=%s\n", asctime(gmtime(&timep)));signal(SIGINT, handler);
}
int main()
{int i;signal(SIGINT, handler);for (i = 1; i <= 100; i++){printf("i=%d\n", i);sleep(1);}printf("the program ends!\n");return 0;
}

编写一段C程序完成：父进程创建一个子进程，父进程对子进程设置一个报警信号，然后父进程等待子进程的结束，如果此时报警信号先到，就终止子进程。在程序中尽量返回子进程的退出码。

#include 
#include 
#include 
#include 
#include 
#include // https://blog.csdn.net/awawfwfw/article/details/46519251void killchild(int pid_child);void killchild(int pid_child)
{printf("killing  child process   \n");//调用wait函数int pidxx;pidxx = wait(NULL);printf("killed the child process, whose pid is %d \n", pidxx);exit(0);
}void killyourself(int ownid);
void killyourself(int ownid)
{// printf("killing  child process %d  \n",pid_child);printf("parent sent signal, child process killed itself  \n");exit(0);
}int main()
{// 要捕捉的信号(void)signal(SIGALRM, killchild);int pid_child = 0;int pid = fork();if (pid == -1){perror("fork failed\n");// exit(1);exit(EXIT_FAILURE);}if (pid == 0){//子进程pid_child = getpid();//子进程也signal一个信号(void)signal(SIGHUP, killyourself);sleep(15);kill(getppid(), SIGALRM);}else{//父进程//等待// pause();sleep(6);kill(pid_child, SIGHUP);exit(0);}
}

编写一个C语言程序使其完成：两个程序testl和test2通过一个共享内存进行通信，其中testl向共享内存中写数据，test2从共享内存中读出数据或信息并将数据或信息送入标准输出上。

test1

#include 
#include 
#include 
#include 
#include 
#include 
#include struct shared_msg
{int update;        //更新数据标志，1：更新，0：未更新char text[BUFSIZ]; //记录写入和读取的文本
};
void main()
{printf("程序开始\n");key_t key;              //共享内存键值int shmid;              //共享内存标识char buf[BUFSIZ];       //输入缓冲struct shared_msg *msg; //共享内存地址//得到键值key = (key_t)1234;//创建共享内存shmid = shmget(key, sizeof(struct shared_msg), IPC_CREAT | 0666);if (shmid < 0){//输出到错误缓冲区fprintf(stderr, "创建共享内存失败\n");exit(EXIT_FAILURE);}//将共享内存段映射到调用进程的数据段中msg = (struct shared_msg *)shmat(shmid, NULL, 0);if (msg < (struct shared_msg *)0){fprintf(stderr, "共享内存段映射到进程失败n");exit(EXIT_FAILURE);}printf("共享内存地址 %X\n", (int*)msg);//向共享内存中写入数据while (1){//向共享内存中写入数据printf("请输入消息:");//从缓冲区输入fgets(buf, BUFSIZ, stdin);strncpy(msg->text, buf, BUFSIZ);msg->update = 1; // 1表示数据更新，客户端要同步更新printf("更新数据完成\n");//写入数据if (strncmp(buf, "EOF", 3) == 0){break;}}//将共享内存和当前进程分离if (shmdt(msg) < 0){fprintf(stderr, "将共享内存和当前进程分离失败\n");exit(EXIT_FAILURE);}printf("程序结束\n");exit(EXIT_SUCCESS);
}

tes2

#include 
#include 
#include 
#include 
#include 
#include 
#include struct shared_msg
{int update;        //更新数据标志，1：更新，0：未更新char text[BUFSIZ]; //记录写入和读取的文本
};
void main()
{printf("程序开始\n");key_t key;              //共享内存键值int shmid;              //共享内存标识struct shared_msg *msg; //共享内存地址char buf[BUFSIZ];       //读取缓冲//得到键值key = (key_t)1234;//创建共享内存shmid = shmget(key, sizeof(struct shared_msg), IPC_CREAT | 0666);if (shmid < 0){//输出到错误缓冲区fprintf(stderr, "创建共享内存失败\n");exit(EXIT_FAILURE);}//将共享内存段映射到调用进程的数据段中msg = (struct shared_msg *)shmat(shmid, NULL, 0);if (msg < (struct shared_msg *)0){fprintf(stderr, "共享内存段映射到进程失败n");exit(EXIT_FAILURE);}printf("共享内存地址 %X\n", (int*)msg);//向共享内存中写入数据while (1){//服务端更新数据则读取while (msg->update == 1){sprintf(buf, "%s", msg->text);printf("读取数据:%s", buf);//读取完成后，将更新标志改变msg->update = 0;}if (strncmp(buf, "EOF", 3) == 0){break;}}//将共享内存和当前进程分离if (shmdt(msg) < 0){fprintf(stderr, "将共享内存和当前进程分离失败\n");exit(EXIT_FAILURE);}//删除共享内存if (shmctl(shmid, IPC_RMID, 0) == -1){fprintf(stderr, "删除共享内存失败\n");exit(EXIT_FAILURE);}printf("程序结束\n");exit(EXIT_SUCCESS);
}