厦门建设网站首页网站推广的方法及技巧

1.有三个线程，ID号分别为ABC，且每个线程中都在循环打印自己的ID。要求打印的结果为ABC。

用同步互斥方法控制先后顺序

用条件变量结合互斥锁来实现

#include <myhead.h>pthread_t pid1,pid2, pid3;
pthread_cond_t cid1,cid2,cid3;
pthread_mutex_t mid;int flag=0;void* pthreadA(void* arg){  //flag:0时运行while(1){//上锁pthread_mutex_lock(&mid);//判断是否应该解锁退出并休眠if(flag!=0){pthread_cond_wait(&cid1,&mid);}//临界区printf("A");//修改下一个访问条件flag=1;//唤醒其他线程pthread_cond_signal(&cid2);//解锁pthread_mutex_unlock(&mid);}pthread_exit(NULL);
}void* pthreadB(void* arg){   //flag:1时运行while(1){//上锁pthread_mutex_lock(&mid);//判断是否符合条件if(flag!=1){pthread_cond_wait(&cid2,&mid);}//临界值printf("B");//修改下一个访问条件flag=2;//唤醒其他线程pthread_cond_signal(&cid3);//解锁pthread_mutex_unlock(&mid);}pthread_exit(NULL);
}void* pthreadC(void* arg){   //flag:2时运行while(1){//上锁pthread_mutex_lock(&mid);//判断是否符合条件if(flag!=2){pthread_cond_wait(&cid3,&mid);}//临界值printf("C");//修改下一个访问条件flag=0;//唤醒其他线程pthread_cond_signal(&cid1);//解锁pthread_mutex_unlock(&mid);}pthread_exit(NULL);
}int main(int argc, const char *argv[])
{//创建互斥锁pthread_mutex_init(&mid,NULL);//创建条件变量pthread_cond_init(&cid1,NULL);pthread_cond_init(&cid2,NULL);pthread_cond_init(&cid3,NULL);//创建线程if((pthread_create(&pid1,NULL,pthreadA,NULL))<0){printf("create pthreadA fail\n");return -1;}if((pthread_create(&pid2,NULL,pthreadB,NULL))<0){printf("create pthreadB fail\n");return -1;}if((pthread_create(&pid3,NULL,pthreadC,NULL))<0){printf("create pthreadC fail\n");return -1;}//回收线程pthread_join(pid1,NULL);pthread_join(pid2,NULL);pthread_join(pid3,NULL);//销毁条件变量pthread_cond_destroy(&cid1);pthread_cond_destroy(&cid2);pthread_cond_destroy(&cid3);//销毁锁pthread_mutex_destroy(&mid);return 0;
}

2.实现AB进程对话

A进程发送一句话后，B进程接收到打印。然后B进程发送一句话，A进程接收后打印b。

重复上述步骤。直到AB接收或者发送完quit后，结束AB进程

chatA

#include <myhead.h>int main(int argc, const char *argv[])
{umask(0);//创建有名管道文件if(mkfifo("./fifo",0664)<0){if(errno!=17){perror("mkfifo");return -1;}}printf("mkfifo success\n");char buf[128]="";ssize_t res=0;while(1){//写打开管道文件int fd=open("./fifo",O_WRONLY);if(fd<0){perror("open");return -1;}bzero(buf,sizeof(buf));//获取信息fgets(buf,sizeof(buf),stdin);buf[strlen(buf)-1]='\0';//写入管道文件if(write(fd,buf,sizeof(buf))<0){perror("write");return -1;}printf("发送成功\n");if(strcmp(buf,"quit")==0){break;}close(fd);//读打开管道文件fd=open("./fifo",O_RDONLY);if(fd<0){perror("open");return -1;}res=read(fd,buf,sizeof(buf));if(res<0){perror("read");return -1;}else if(0==res){printf("对方进程结束\n");break;}printf("B:%s\n",buf);if(strcmp(buf,"quit")==0){break;}                                 close(fd);}return 0;
}

chatB

#include <myhead.h>
int main(int argc, const char *argv[])
{umask(0);if(mkfifo("./fifo",0664)<0){if(errno!=17){perror("mkfifo");return -1;}}printf("mkfifo success\n");char buf[128]="";int res=0;while(1){//读打开管道文件int fd=open("./fifo",O_RDONLY);if(fd<0){perror("open");return -1;                       }bzero(buf,sizeof(buf));res=read(fd,buf,sizeof(buf));if(res<0){perror("read");return -1;}if(res==0){printf("对方进程结束\n");break;}printf("A:%s\n",buf);if(strcmp(buf,"quit")==0){break;}close(fd);//写fd=open("./fifo",O_WRONLY);if(fd<0){perror("open");return -1;                       }bzero(buf,sizeof(buf));fgets(buf,sizeof(buf),stdin);buf[strlen(buf)-1]='\0';if(write(fd,buf,sizeof(buf))<0){perror("write");return -1;}printf("发送成功\n");if(strcmp(buf,"quit")==0){break;}close(fd);}return 0;
}