1.将一个文件中的数据打印到终端上,类似cat一个文件。要求如下
a.A线程读取文件中的数据
b.B线程将A线程读取到的数据打印到终端上
c.C文件打印完毕后,结束进程
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <pthread.h>
#include <semaphore.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
sem_t sem1;
sem_t sem2;
ssize_t res=0;
char str[20]="";
void* readCallback(void* arg)
{
int fd=open("./01_cond.c",O_RDONLY);
if(fd<0)
{
perror("open");
pthread_exit(NULL);
}
while(1)
{
sem_wait(&sem1);
bzero(str,sizeof(str));
res=read(fd,str,sizeof(str));
if(0==res)
{
sem_post(&sem2);
pthread_exit(NULL);
}
if(res<0)
{
perror("read");
pthread_exit(NULL);
}
sem_post(&sem2);
}
pthread_exit(NULL);
}
void* writeCallback(void* arg)
{
while(1)
{
sem_wait(&sem2);
if(write(1,str,res)<=0)
{
break;
}
sem_post(&sem1);
}
pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{
if(sem_init(&sem1,0,1)!=0)
{
perror("sem_init");
return -1;
}
if(sem_init(&sem2,0,1)!=0)
{
perror("sem_init");
return -1;
}
pthread_t tid1,tid2;
if(pthread_create(&tid1,NULL,readCallback,NULL)!=0)
{
perror("pthread_create");
return -1;
}
if(pthread_create(&tid1,NULL,writeCallback,NULL)!=0)
{
perror("pthread_create");
return -1;
}
pthread_join(tid1,NULL);
pthread_join(tid2,NULL);
sem_destroy(&sem1);
sem_destroy(&sem2);
return 0;
}
2.用条件变量实现,有编号为ABC的三个线程,线程内分别打印自己的线程编号,要求打印的顺序为ABC
#include<stdio.h>
#include <pthread.h>
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond1 = PTHREAD_COND_INITIALIZER;
pthread_cond_t cond2 = PTHREAD_COND_INITIALIZER;
pthread_cond_t cond3 = PTHREAD_COND_INITIALIZER;
int flag = 0;
void* callBackA(void* arg)
{
while(1)
{
pthread_mutex_lock(&mutex);
if(flag != 0)
{
pthread_cond_wait(&cond1, &mutex);
}
printf("A");
flag = 2;
pthread_cond_signal(&cond2);
pthread_mutex_unlock(&mutex);
}
pthread_exit(NULL);
}
void* callBackB(void* arg)
{
while(1)
{
pthread_mutex_lock(&mutex);
if(flag != 1)
{
pthread_cond_wait(&cond2, &mutex);
}
printf("B");
flag = 0;
pthread_cond_signal(&cond3);
pthread_mutex_unlock(&mutex);
}
pthread_exit(NULL);
}
void* callBackC(void* arg)
{
while(1)
{
pthread_mutex_lock(&mutex);
if(flag != 2)
{
pthread_cond_wait(&cond3, &mutex);
}
printf("C");
flag = 0;
pthread_cond_signal(&cond1);
pthread_mutex_unlock(&mutex);
}
pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{
pthread_t tid,tid1,tid2;
if(pthread_create(&tid, NULL, callBackA, NULL) != 0)
{
fprintf(stderr, "pthread_create failed\n");
return -1;
}
if(pthread_create(&tid1, NULL, callBackB, NULL) != 0)
{
fprintf(stderr, "pthread_create failed\n");
return -1;
}
if(pthread_create(&tid2, NULL, callBackC, NULL) != 0)
{
fprintf(stderr, "pthread_create failed\n");
return -1;
}
pthread_join(tid, NULL);
pthread_join(tid1, NULL);
pthread_join(tid2, NULL);
pthread_mutex_destroy(&mutex);
pthread_cond_destroy(&cond1);
pthread_cond_destroy(&cond2);
pthread_cond_destroy(&cond3);
return 0;
}
3.要求用信号量的方式实现,打印一次倒置一次。不允许使用flag
#include <stdio.h>
#include <pthread.h>
#include <string.h>
#include <semaphore.h>
char str[]="1234567";
sem_t sem1;
sem_t sem2;
void* callBack_print(void* arg)
{
while(1)
{
sem_wait(&sem1);
printf("%s\n", str);
sem_post(&sem2);
}
pthread_exit(NULL);
}
void* callBack_swap(void* arg)
{
int len = strlen(str);
char temp;
int i = 0;
while(1)
{
sem_wait(&sem2);
for(i=0; i<len/2; i++)
{
temp = str[i];
str[i] = str[len-1-i];
str[len-1-i] = temp;
}
sem_post(&sem1);
}
pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{
if(sem_init(&sem1,0,1)<0)
{
perror("sem_init");
return -1;
}
if(sem_init(&sem2,0,1)<0)
{
perror("sem_init");
return -1;
}
pthread_t tid1,tid2;
if(pthread_create(&tid1,NULL,callBack_print,NULL)!=0)
{
return -1;
}
if(pthread_create(&tid2,NULL,callBack_swap,NULL)!=0)
{
return -1;
}
pthread_join(tid1,NULL);
pthread_join(tid2,NULL);
sem_destroy(&sem1);
sem_destroy(&sem2);
return 0;
}