c++ thread join detach用法

c++ thread join用法

#include <thread>
#include <mutex>
#include <iostream>

using namespace std;

void downlaod1()
{
	cout<<"d1"<<endl;

	for (int i = 0; i < 100; ++i)
	{
		/* code */
		std::this_thread::sleep_for(chrono::milliseconds(50));
		cout <<"下载进度1...."<< i<<endl;
	}
	cout <<"d1 successful!"<<endl;
}

void downlaod2()
{
	cout<<"d2"<<endl;

	for (int i = 0; i < 100; ++i)
	{
		/* code */
		std::this_thread::sleep_for(chrono::milliseconds(80));
		cout<<"下载进度2...."<< i<<endl;
	}
	cout <<"下载完成2"<<endl;
}


void process()
{
	cout <<"start process d1 and d2!\n"<<endl;
}

int main(int argc, char const *argv[])
{
	/* code */
	cout<<"main run!\n";

	thread d2(downlaod2);
	downlaod1();
	d2.join();

	process();

	return 0;
}

1. g++ _thread_join.cpp -o test -lpthread
2. -lpthread必须加上，不加会报thread_creat不存在的错误
3. 
   从上面的结果看到，d2.join()的加入会使线程download1做完事情后，等待线程download2结束，共同执行process(),所以join()是必须等到线程执行完毕后返回

detach

#include <thread>
#include <iostream>
#include <mutex>

using namespace std;

void download1()
{
	for (int i = 0; i < 100; ++i)
	{
		/* code */
		std::this_thread::sleep_for(chrono::milliseconds(5));
		cout<<"d1 进度 ......"<< i<<endl;
	}
	cout<<"d1 sucessful!\n"<<endl;
}

void download2()
{
	for (int i = 0; i < 100; ++i)
	{
		/* code */
		this_thread::sleep_for(chrono::milliseconds(5));
		cout<<"d2 进度........"<<endl;
	}
	cout<<"d2 sucessful!\n"<<endl;
}

void process()
{
	cout<<"d1 ok ,d2 ok"<<endl;
}


int main(int argc, char const *argv[])
{
	/* code */
	cout<<"main run!\n"<<endl;
	
	thread d1(download1);
	thread d2(download2);

	d1.detach();//detach 使主线程与子线程并行执行
	d2.detach();

	for (int i = 0; i < 5; ++i)
	{
		/* code */
		this_thread::sleep_for(chrono::milliseconds(15));
		cout <<"main run process..."<< i<<endl;

	}

	process();


	return 0;
}

1. 
   对于join来说，detach使主线程和子线程并行，这样就不会应用join时候，带来的主线程阻塞的问题