线程的使用
1.线程的创建
线程的相关操作放在<pthread.h>中。
1.1我们定义一个线程,首先要进行定义一个函数,类似我们创建一个a线程
void *thread_a(void *in){
printf("Im thread_a
");
pthread_exit((void*)0);
}
1.2.创建一个线程
pthread_t a;//声明
pthread_create(&a,NULL,thread_a,(void*)0);//创建线程
1.3.创建3个线程并且打印(如果你打印1000个,并且睡一秒,会发现,这个进程实际上运行是无序的)
#include <stdio.h>
#include <pthread.h>
void *thread_a(void *in){
printf("Im thread_a
");
pthread_exit((void*)0);
}
void *thread_b(void *in){
printf("Im thread_b
");
pthread_exit((void*)0);
}
void *thread_c(void *in){
printf("Im thread_c
");
pthread_exit((void*)0);
}
int main(){
pthread_t a,b,c;
int val;
/**create thread a,b,c*/
pthread_create(&a,NULL,thread_a,(void*)0);
pthread_create(&b,NULL,thread_b,(void*)0);
pthread_create(&c,NULL,thread_c,(void*)0);
/**main thread waits for termination of a,b,c*/
pthread_join(a,(void**)0);
pthread_join(b,(void**)0);
pthread_join(c,(void**)0);
printf("Main thread is over
");
return 0;
}
3.如果我们希望线程进行打印顺序为c,b,a,那么我们可以定义一个信号。
线程a等待线程2的信号,线程2等待线程3的信号
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>//sem_wait sem_init这些方法全在里面
sem_t sem1;
sem_t sem2;
void *thread_a(void *in){
sem_wait(&sem1);/*wait for sem1*/
printf("Im thread_a
");
pthread_exit((void*)0);
}
void *thread_b(void *in){
sem_wait(&sem2);/*wait for sem2*/
printf("Im thread_b
");
sem_post(&sem1);/*increase sem1 by 1,make thread_a run*/
pthread_exit((void*)0);
}
void *thread_c(void *in){
printf("Im thread_c
");
sem_post(&sem2);/*increase sem2 by 1,make thread_b run*/
pthread_exit((void*)0);
}
int main(){
pthread_t a,b,c;
int val;
/**init sem1 sem2 to 0,any thread waits for it will be blocked*/
sem_init(&sem1,0,0);
sem_init(&sem2,0,0);
/**create thread a,b,c*/
pthread_create(&a,NULL,thread_a,(void*)0);
pthread_create(&b,NULL,thread_b,(void*)0);
pthread_create(&c,NULL,thread_c,(void*)0);
/**main thread waits for termination of a,b,c*/
pthread_join(a,(void**)0);
pthread_join(b,(void**)0);
pthread_join(c,(void**)0);
printf("Main thread is over
");
/*destroy sem1,sem2*/
sem_destroy(&sem1);
sem_destroy(&sem2);
return 0;
}
2.锁的创建和使用
2.1.mutex互斥锁的创建
互斥锁的内容:我们要想创建一个互斥锁,首先是对这个mutex进行初始化操作。
互斥锁的头文件在<pthread.h>中。
pthread_mutex_t mutex;//声明一个锁
pthread_mutex_lock(&mutex);
pthread_mutex_unlock(&mutex);
//加锁和解锁操作
pthread_mutex_destory(&mutex);//销毁锁的操作
2.2.编写一个读写(线程分离)的程序,读一个空串,然后写进另一个数组里面
#include <string.h>
#include <unistd.h>
#include <pthread.h>
#include <stdio.h>
pthread_mutex_t mutex;
char buf[80],buf1[80];
int n,buf_has_item=0;
void writer_function(void){
while(1){
pthread_mutex_lock(&mutex);
if(buf_has_item==0){
printf("等待从键盘读一个非空串:
");
if((n=read(0,buf,sizeof(buf)))>0)
buf_has_item=1;
printf("A thread write:%s
",buf);
}
pthread_mutex_unlock(&mutex);
}
}
void reader_function(void){
while(1){
pthread_mutex_lock(&mutex);
if(buf_has_item==1){
strcpy(buf1,buf);
buf_has_item=0;
printf("A thread read:%s
",buf1);
}
pthread_mutex_unlock(&mutex);
}
}
void *thread_reader(void *in){
reader_function();
pthread_exit((void**)0);
}
int main(){
pthread_t reader,writer;pthread_t ptr;
pthread_mutex_init(&mutex,NULL);
pthread_create(&ptr,NULL,thread_reader,(void*)0);//创建一个线程
writer_function();
pthread_join(ptr,(void**)0);
return 0;
}