如何使用C ++ / C ++ 11打印当前时间(以毫秒为单位) [英] How to print current time (with milliseconds) using C++ / C++11
问题描述
目前我使用此代码
string now(){
time_t t = time(0);
char buffer [9] = {0};
strftime(buffer,9,%H:%M:%S,localtime(& t));
return string(buffer);
}
我需要添加毫秒,所以输出具有格式: 16:56:12.321
您可以使用 Boost的Posix时间 。
您可以使用 boost :: posix_time :: microsec_clock :: local_time()
来获取当前时间分辨率时钟:
boost :: posix_time :: ptime now = boost :: posix_time :: microsec_clock :: local_time
然后您可以计算当天的时间偏移(因为您的持续时间输出为< hours>:< hours>:< minutes>:< seconds>。< milliseconds>
,我假设他们是以当前日期抵消计算的;如果不是,使用另一个起始点的持续时间/时间间隔):
boost :: posix_time :: time_duration td = now.time_of_day();然后你可以使用 .hours()
。 , .minutes()
, .seconds()
访问器获取相应的值。
不幸的是,似乎没有 .milliseconds()
访问器,但是有一个 .total_milliseconds()
一;所以你可以做一个减法数学得到剩余的毫秒格式化在字符串中。
然后你可以使用 sprintf code>(或 sprintf()_ s
如果您对非便携式VC ++ - 唯一代码感兴趣)将这些字段格式化为原始 char
缓冲区,并将这个原始C字符串缓冲区安全地包装到一个强大的方便的 std :: string
实例中。
有关详细信息,请参阅下面的注释代码。
在控制台中输出如下:
< blockquote>
11:43:52.276
示例代码:
////////////////// ////////////////////////////////////////////////// ///////////
#include< stdio.h> // for sprintf()
#include< iostream> // for console output
#include< string> // for std :: string
#include< boost / date_time / posix_time / posix_time.hpp>
// ------------------------------------ -----------------------------------------
//格式化当前时间(以当前日的偏移量计算):
//
//hh:mm:ss.SSS(其中SSS是毫秒)
// - -------------------------------------------------- -------------------------
std :: string now_str()
{
//获取当前时间从时钟,使用微秒解决
const boost :: posix_time :: ptime now =
boost :: posix_time :: microsec_clock :: local_time();
//获取当前日期的时间偏移量
const boost :: posix_time :: time_duration td = now.time_of_day();
//
//提取小时,分钟,秒和毫秒。
//
//因为没有直接访问器.milliseconds(),
//毫秒是通过在毫秒之间的差值_
//计算的访问器)和以前读取的小时/分钟/秒
//值。
//
const long hours = td.hours();
const long minutes = td.minutes();
const long seconds = td.seconds();
const long milliseconds = td.total_milliseconds() -
((小时* 3600 +分钟* 60 +秒)* 1000);
//
//格式如下:
//
// hh:mm:ss.SSS
//
/ / eg 02:15:40:321
//
// ^ ^
// | |
// 123456789 * 12
// --------- 10- - > 12 chars + \0 - > 13个字符应该足够
//
//
char buf [40];
sprintf(buf,%02ld:%02ld:%02ld。%03ld,
小时,分钟,秒,毫秒);
return buf;
}
int main()
{
std :: cout< now_str()<< '\\\
';
}
////////////////////////////////////// ///////////////////////////////////////// b $ b
Currently I use this code
string now() {
time_t t = time(0);
char buffer[9] = {0};
strftime(buffer, 9, "%H:%M:%S", localtime(&t));
return string(buffer);
}
to format time. I need to add milliseconds, so the output has the format: 16:56:12.321
解决方案 You can use Boost's Posix Time.
You can use boost::posix_time::microsec_clock::local_time()
to get current time from microseconds-resolution clock:
boost::posix_time::ptime now = boost::posix_time::microsec_clock::local_time();
Then you can compute time offset in current day (since your duration output is in the form <hours>:<minutes>:<seconds>.<milliseconds>
, I'm assuming they are calculated as current day offset; if they are not, feel free to use another starting point for duration/time interval):
boost::posix_time::time_duration td = now.time_of_day();
Then you can use .hours()
, .minutes()
, .seconds()
accessors to get the corresponding values.
Unfortunately, there doesn't seem to be a .milliseconds()
accessor, but there is a .total_milliseconds()
one; so you can do a little subtraction math to get the remaining milliseconds to be formatted in the string.
Then you can use sprintf()
(or sprintf()_s
if you are interested in non-portable VC++-only code) to format those fields into a raw char
buffer, and safely wrap this raw C string buffer into a robust convenient std::string
instance.
See the commented code below for further details.
Output in console is something like:
11:43:52.276
Sample code:
///////////////////////////////////////////////////////////////////////////////
#include <stdio.h> // for sprintf()
#include <iostream> // for console output
#include <string> // for std::string
#include <boost/date_time/posix_time/posix_time.hpp>
//-----------------------------------------------------------------------------
// Format current time (calculated as an offset in current day) in this form:
//
// "hh:mm:ss.SSS" (where "SSS" are milliseconds)
//-----------------------------------------------------------------------------
std::string now_str()
{
// Get current time from the clock, using microseconds resolution
const boost::posix_time::ptime now =
boost::posix_time::microsec_clock::local_time();
// Get the time offset in current day
const boost::posix_time::time_duration td = now.time_of_day();
//
// Extract hours, minutes, seconds and milliseconds.
//
// Since there is no direct accessor ".milliseconds()",
// milliseconds are computed _by difference_ between total milliseconds
// (for which there is an accessor), and the hours/minutes/seconds
// values previously fetched.
//
const long hours = td.hours();
const long minutes = td.minutes();
const long seconds = td.seconds();
const long milliseconds = td.total_milliseconds() -
((hours * 3600 + minutes * 60 + seconds) * 1000);
//
// Format like this:
//
// hh:mm:ss.SSS
//
// e.g. 02:15:40:321
//
// ^ ^
// | |
// 123456789*12
// ---------10- --> 12 chars + \0 --> 13 chars should suffice
//
//
char buf[40];
sprintf(buf, "%02ld:%02ld:%02ld.%03ld",
hours, minutes, seconds, milliseconds);
return buf;
}
int main()
{
std::cout << now_str() << '\n';
}
///////////////////////////////////////////////////////////////////////////////
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