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;
}