1，思维导图

2，使用两个线程分别复制文件的上下两部分到同一个文件

#include<myhead.h>
sem_t fastsem;
//pthread_mutex_t fastmutex;
void *capy_up(void *c)
{
//	pthread_mutex_lock(&fastmutex);
	int len=*(int *)c;
	int fp1=open("./1.txt",O_RDONLY);
	int fp2=open("./2.txt",O_WRONLY);
	char str[5];
	int read_cs;
	int count=0;
	while(count<len/2&&(read_cs=read(fp1,str,sizeof(str)))>0)
	{
		count+=read_cs;
		if(count>len/2)
		{
			write(fp2,str,(read_cs-(count-len/2)));
			break;
		}
		write(fp2,str,read_cs);
	}
	close(fp1);
	close(fp2);
	sem_post(&fastsem);
//	pthread_mutex_unlock(&fastmutex);
	pthread_exit(NULL);
}
void *capy_dn(void *c)
{
//	pthread_mutex_lock(&fastmutex);
	sem_wait(&fastsem);
	int len=*(int *)c;
	int fp3=open("./1.txt",O_RDONLY);
	int fp4=open("./2.txt",O_WRONLY|O_APPEND);
	lseek(fp3,len/2,SEEK_SET);
	char str[5];
	int read_cs;
	int count=0;
	while((read_cs=read(fp3,str,sizeof(str)))>0)
	{
		write(fp4,str,read_cs);
	}
	close(fp3);
	close(fp4);
//	pthread_mutex_unlock(&fastmutex);
	sem_post(&fastsem);
	pthread_exit(NULL);
}

int main(int argc, const char *argv[])
{
//	pthread_mutex_init(&fastmutex,NULL);
	sem_init(&fastsem,0,0);
	int fp1=open("./1.txt",O_RDONLY);
	int fp2=open("./2.txt",O_WRONLY|O_CREAT|O_TRUNC,0664);
	int len=lseek(fp1,0,SEEK_END);
	close(fp1);
	close(fp2);
	pthread_t tid1;
	int k1=pthread_create(&tid1,NULL,capy_up,&len);
	pthread_t tid2;
	int k2=pthread_create(&tid2,NULL,capy_dn,&len);
	if(k1!=0||k2!=0)
	{
		perror("ptcreat");
		return -1;
	}
//	pthread_mutex_destroy(&fastmutex);
	sem_destroy(&fastsem);
	pthread_join(tid1,NULL);
	pthread_join(tid2,NULL);
	return 0;
}

3，使用四个线程通过无名信号量实现 “春“ ”夏“ ”秋“ ”冬“ 循环

#include<myhead.h>
sem_t sem1,sem2,sem3,sem4;
void *fun1(void *c)
{
	while(1)
	{
		sem_wait(&sem4);
		sleep(1);
		printf("春\t");
		fflush(stdout);
		sem_post(&sem3);
	}
	pthread_exit(NULL);
}
void *fun2(void *x)
{
	while(1)
	{
		sem_wait(&sem3);
		sleep(1);
		printf("夏\t");
		fflush(stdout);
		sem_post(&sem2);
	}
	pthread_exit(NULL);
}
void *fun3(void *q)
{
	while(1)
	{
		sem_wait(&sem2);
		sleep(1);
		printf("秋\t");
		fflush(stdout);
		sem_post(&sem1);
	}
	pthread_exit(NULL);
}
void *fun4(void *d)
{
	while(1)
	{
		sem_wait(&sem1);
		sleep(1);
		printf("冬\t");
		fflush(stdout);
		sem_post(&sem4);
	}
	pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{
	sem_init(&sem1,0,0);
	sem_init(&sem2,0,0);
	sem_init(&sem3,0,0);
	sem_init(&sem4,0,1);
	pthread_t tid1,tid2,tid3,tid4;
	if(pthread_create(&tid1,NULL,fun1,NULL)!=0)
	{
		perror("ptcreat1");
		return -1;
	}
	if(pthread_create(&tid2,NULL,fun2,NULL)!=0)
	{
		perror("ptcreat1");
		return -1;
	}
	if(pthread_create(&tid3,NULL,fun3,NULL)!=0)
	{
		perror("ptcreat1");
		return -1;
	}
	if(pthread_create(&tid4,NULL,fun4,NULL)!=0)
	{
		perror("ptcreat1");
		return -1;
	}
	sem_destroy(&sem1);
	sem_destroy(&sem2);
	sem_destroy(&sem3);
	sem_destroy(&sem4);
	pthread_join(tid1,NULL);
	pthread_join(tid2,NULL);
	pthread_join(tid3,NULL);
	pthread_join(tid4,NULL);
	return 0;
}