用信号量的方式实现打印1234567后打印7654321循环交替打印。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<head.h>
char buf[]="1234567";
sem_t sem;
void *callBack1(void *arg)
{int i=0;int s=strlen(buf)-1;while(i<s){int t=buf[i];buf[i]=buf[s];buf[s]=t;i++;s--;}pthread_exit(NULL);
}
void *callBack2(void *arg)
{printf("%s\n",buf);sem_post(&sem);pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{sem_init(&sem,0,1);while(1){pthread_t pid1,pid2;sem_wait(&sem);if(pthread_create(&pid2,NULL,callBack2,NULL)!=0){fprintf(stderr,"failed __%d__\n",__LINE__);return -1;}pthread_detach(pid2);sem_post(&sem);sem_wait(&sem);if(pthread_create(&pid1,NULL,callBack1,NULL)!=0){fprintf(stderr,"failed __%d__\n",__LINE__);return -1;}pthread_join(pid1,NULL);}sem_destroy(&sem);return 0;
}

创建两个线程，其中一个线程读取文件中的数据，另一个线程将读取到的内容打印到终端上，类似cat一个文件。

#include<stdio.h>
#include<string.h>
#include<stdlib.h>
#include<head.h>
pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t cond=PTHREAD_COND_INITIALIZER;
int flag=0;
void *callBack1(void*arg)
{int fd=open("./10.c",O_RDONLY);if(fd<0){ERR_MSG("open");return NULL;}lseek(fd,0,SEEK_SET);char c;while(1){pthread_mutex_lock(&mutex);if(flag!=0)pthread_cond_wait(&cond,&mutex);ssize_t res=read(fd,&c,1);if(res==0){pthread_mutex_unlock(&mutex);break;}*(char*)arg=c;flag=1;pthread_cond_signal(&cond);pthread_mutex_unlock(&mutex);}pthread_exit(NULL);
}
void *callBack2(void*arg)
{while(1){pthread_mutex_lock(&mutex);if(flag!=1)pthread_cond_wait(&cond,&mutex);char c=*(char*)arg;printf("%c",c);flag=0;pthread_cond_signal(&cond);pthread_mutex_unlock(&mutex);}pthread_exit(NULL);
}
int main(int argc, const char *argv[])
{pthread_t tid1,tid2;char tmp_c=-1;if(pthread_create(&tid1,NULL,callBack1,(void*)&tmp_c)!=0){fprintf(stderr,"failed __%d__\n",__LINE__);return -1;}if(pthread_create(&tid2,NULL,callBack2,(void*)&tmp_c)!=0){fprintf(stderr,"failed __%d__\n",__LINE__);return -1;}pthread_join(tid1,NULL);pthread_cancel(tid2);pthread_mutex_destroy(&mutex);pthread_cond_destroy(&cond);return 0;
}