IOday6

1.创建两个线程，分支线程1拷贝文件的前一部分，分支线程2拷贝文件的后一部分

 #include <head.h>
 void* frist(void* arg)
 {
         //打开文件
         int fd=open("../4.c",O_RDONLY);
         //创建拷贝文件
         int fd1=open("./2.c",O_RDWR|O_CREAT,0664);
         //读取文件大小
         off_t size=lseek(fd,0,SEEK_END);
         //重置光标位置
         lseek(fd,0,SEEK_SET);
         //前半段内容
         char* buf=malloc(size/2+1);
         size_t res=read(fd,buf,size/2);
         write(fd1,buf,size/2);
         printf("%ld\n",size);
         printf("%ld\n",res);
 
         //关闭文件
         free(buf);
         close(fd);
         close(fd1);
         pthread_exit(NULL);
 }
 void* last(void* arg)
 {
     //打开文件
     int fd=open("../4.c",O_RDONLY);
     //创建拷贝文件
     int fd1=open("./2.c",O_RDWR|O_CREAT,0664);
     //读取文件大小                                                                 
     off_t size=lseek(fd,0,SEEK_END);
     //获得剩余要写入的数据
     off_t m=size-size/2;
     //重置光标位置
     lseek(fd,size/2,SEEK_SET);
     lseek(fd1,size/2,SEEK_SET);
     //读取后半段内容
     char* buf=malloc(size/2+1);
     size_t res=read(fd,buf,size/2);
         write(fd1,buf,size/2-1);
         printf("%ld\n",size);
         printf("%ld\n",res);
         //关闭文件
         free(buf);
         close(fd);
         close(fd1);
         pthread_exit(NULL);
 }
 
 int main(int argc, const char *argv[])
 {
     //创建两个分支线程
     pthread_t pth1,pth2;
     if((errno=pthread_create(&pth1,NULL,frist,NULL))!=0)
         PRINT_ERROR("pthread_create1 error");
     if((errno=pthread_create(&pth2,NULL,last,NULL))!=0)
         PRINT_ERROR("pthread_create2 error");
     pthread_join(pth1,NULL);
     pthread_join(pth2,NULL);
 
     return 0;
 }
                                                                                    

2.创建3个线程，线程A打印A，线程B打印B，线程C打印C，要求重复打印顺序ABC (分别使用信号量和条件变量实现)

 信号量：

 
 #include <head.h>
 sem_t sem1,sem2,sem3;
 void* funA(void* arg)
 {
     while(1)
     {
         //P操作 -1
         sem_wait(&sem1);
         printf("A\n");
         //V操作
         sem_post(&sem2);
     }
     pthread_exit(NULL);
 }
 void* funB(void* arg)
 {
     while(1)
     {
         sleep(1);
         //P操作 -1
         sem_wait(&sem2);
         printf("B\n");
         //V操作
         sem_post(&sem3);                                                  
     }
     pthread_exit(NULL);
 }
 void* funC(void* arg)
 {
     while(1)
     {
         sleep(1);
         //P操作 -1
         sem_wait(&sem3);
         printf("C\n");
         //V操作
         sem_post(&sem1);
     }
     pthread_exit(NULL);
 }
 int main(int argc, const char *argv[])
 {
     //信号量初始化
     if(sem_init(&sem1,0,1))
         PRINT_ERROR("sem_init1 error");
     if(sem_init(&sem2,0,1))
         PRINT_ERROR("sem_init2 error");
     if(sem_init(&sem1,0,1))
         PRINT_ERROR("sem_init3 error");
     //创建分支线程
     pthread_t pth1,pth2,pth3;
     if((errno=pthread_create(&pth1,NULL,funA,NULL))!=0)
         PRINT_ERROR("pthread_create1 error");
     if((errno=pthread_create(&pth2,NULL,funB,NULL))!=0)
         PRINT_ERROR("pthread_create2 error");
     if((errno=pthread_create(&pth3,NULL,funC,NULL))!=0)
         PRINT_ERROR("pthread_create3 error");
     //回收分支
     pthread_join(pth1,NULL);
     pthread_join(pth2,NULL);
     pthread_join(pth3,NULL);
     //销毁信号量
     sem_destroy(&sem1);
     sem_destroy(&sem2);
     sem_destroy(&sem3);
     return 0;
 }
                                                                           
                                                                           
                                                                           

条件变量：

#include <head.h>
pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;
pthread_cond_t cond3 = PTHREAD_COND_INITIALIZER;
pthread_mutex_t mutex= PTHREAD_MUTEX_INITIALIZER;
int flag=0;
void* funA(void* arg)
{
    while(1)
    {
        pthread_mutex_lock(&mutex);
        while(flag!=0)
            pthread_cond_wait(&cond1,&mutex);
        flag=1;
        printf("A\n");
        pthread_cond_signal(&cond2);
        pthread_mutex_unlock(&mutex);
    }
    pthread_exit(NULL);
}
void* funB(void* arg)
{
    while(1)
    {                                                                          
        pthread_mutex_lock(&mutex);
        while(flag!=1)
            pthread_cond_wait(&cond2,&mutex);
        flag=2;
        printf("B\n");
        pthread_cond_signal(&cond3);
        pthread_mutex_unlock(&mutex);
    }
    pthread_exit(NULL);
}
void* funC(void* arg)
{
    while(1)
    {
        pthread_mutex_lock(&mutex);
        while(flag!=2)
            pthread_cond_wait(&cond3,&mutex);
        flag=0;
        printf("C\n");
        pthread_cond_signal(&cond1);
        pthread_mutex_unlock(&mutex);
    }
    pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{
    //创建分支线程
    pthread_t pth1,pth2,pth3;
    if((errno=pthread_create(&pth1,NULL,funA,NULL))!=0)
        PRINT_ERROR("pthread_create1 error");
    if((errno=pthread_create(&pth2,NULL,funB,NULL))!=0)
        PRINT_ERROR("pthread_create2 error");
    if((errno=pthread_create(&pth3,NULL,funC,NULL))!=0)
        PRINT_ERROR("pthread_create3 error");
    //回收分支
    pthread_join(pth1,NULL);
    pthread_join(pth2,NULL);
    pthread_join(pth3,NULL);
    //销毁条件变量
    pthread_cond_destroy(&cond1);
    pthread_cond_destroy(&cond2);
    pthread_cond_destroy(&cond3);
    return 0;
}