time_t在Linux中的类型其实是long int

struct timeval tv;
gettimeofday(&tv,nullptr);
time_t curTime = tv.tv_sec;   // 获取当前UTC时间戳，单位为秒

#include <chrono>
using namespace chrono;

auto start = system_clock::now();
/*  do something  */
auto end   = system_clock::now();
auto duration = duration_cast<microseconds>(end - start);
cout <<  "花费了"
     << double(duration.count()) * microseconds::period::num / microseconds::period::den
     << "秒" << endl;

有时候可能报错：error: ‘chrono’ in namespace ‘std’ does not name a type

解决方法： 改为using namespace std::chrono; in addition to #include <chrono>

或者用steady_clock

#include <chrono>

using std::chrono::steady_clock;
// 这个类型是 steady_clock::time_point
auto t1 = std::chrono::steady_clock::now();

// 	your code

auto t2 = std::chrono::steady_clock::now();

//秒
double dr_s=std::chrono::duration<double>(t2-t1).count();
//毫秒
double dr_ms=std::chrono::duration<double,std::milli>(t2-t1).count();
//微秒
double dr_us=std::chrono::duration<double,std::micro>(t2-t1).count();
//纳秒
double dr_us=std::chrono::duration<double,std::nano>(t2-t1).count();

ALOAM中的TicToc类其实就是std::chrono::steady_clock::now()

拥有从毫秒到小时的计时

std::chrono::milliseconds 
std::chrono::seconds
std::chrono::minutes 
std::chrono::hours

可以用于休眠函数

std::this_thread::sleep_for(std::chrono::milliseconds(100));
std::this_thread::sleep_for(std::chrono::seconds(1));