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waiting program

anup30 (968)
this program waits 3 sec. the problem is that it continues to use 100% of one CPU thread. How to wait without using CPU ?
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// wait zzzzz
#include <iostream>
#include <ctime>
using namespace std;

int main()
{
    time_t start = time(NULL);  

    while(true)       	
    	if( difftime(time(NULL), start) >= 3 )
    		break;

    cout << "Wall time passed: " << difftime(time(NULL), start) << " second.\n";

return 0;
}
ajh32 (659)
Your code isn't suspending the current thread from processing, it's just iterating through the while(...) condition until the if(...) condition becomes true and exits the while via the break. I think what you are looking for is the Sleep() function.

http://msdn.microsoft.com/query/dev10.query?appId=Dev10IDEF1&l=EN-US&k=k(SLEEP);k(DevLang-%22C%2B%2B%22)&rd=true
AndyMc (6)
I think you can use

std::this_thread::sleep_for

e.g.:

http://www.cplusplus.com/reference/thread/this_thread/sleep_for/

MiiNiPaa (8886)
Modern OS's provide a sleep system call.
And moder C++ provides standard way to do so: http://en.cppreference.com/w/cpp/thread/sleep_for
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#include <chrono>
#include <thread>
 
int main()
{
    std::this_thread::sleep_for( std::chrono::seconds(3) );
}
//Or with C++14
#include <chrono>
#include <thread>
 
using namespace std::literals;

int main()
{
    std::this_thread::sleep_for( 3s );
}
anup30 (968)
thanks for the responses. the code i came to know...
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// its deprecated ... runs, but shows warning in gcc 4.8.1
#include <iostream>
//#include <cstdlib>
using namespace std;

int main() {
cout << 5 << endl;
_sleep(5000); // pauses for 5 seconds
cout << 6 << endl;

return 0;
}

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// sleep_for //C++11
#include <iostream>
#include <chrono>
#include <thread>
using namespace std;

int main() {
cout << 5 << endl;
    std::this_thread::sleep_for(std::chrono::milliseconds(500));  
cout << 6 << endl;

return 0;
}
anup30 (968)
i found another example from
http://www.cplusplus.com/forum/beginner/13906/
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#include <windows.h> ///
#include <iostream>
using namespace std;
int main( ){
    cout << "5" << endl;
    //We use 1000 since Sleep takes the amount of time in milliseconds, and 1000 ms = 1 second
    Sleep( 1000 );

    cout << "4" << endl;
    Sleep( 1000 );
    cout << "3" << endl;
    Sleep( 1000 );
    cout << "2" << endl;
    Sleep( 1000 );
    cout << "1" << endl;
    Sleep( 1000 );

    cout << "Congratulations, you've just wasted 5 seconds of your life!";
    cin.get( );
    
    return 0;
}


it ran without any warning in both visual studio 2012 and in gcc.
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