gettimeofday | 易学教程

time() and gettimeofday() return different seconds

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问题 On the two systems I've tested (a 32-bit Ubuntu 12.04 server and a 64-bit Ubuntu 13.10 VM), the seconds since the epoch given by time() may differ from gettimeofday()'s. Specifically, though I call time() after calling gettimeofday() , the value returned by time() is sometimes less than the tv_sec value returned by gettimeofday() . This apparently occurs just after the clock rolls over to a new second. This caused bugs in some of my code that expected time()'s and gettimeofday()'s seconds to

Linux时间操作(time、gettimeofday)

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一、time函数 #include <time.h> time_t time (time_t *calptr); 返回距计算机元年的秒数一旦取得这种以秒计的很大的时间值后，通常要调用另一个时间函数将其变换为人们可读的时间和日期 #include <time.h> //calendar time into a broken-down time expressed as UTC struct tm * gmtime (const time_t *calptr); //converts the calendar time to the local time , taking into account the local time zone and //daylight saving time flag struct tm * localtime (const time_t *calptr); //converts it into a time_t value time_t mktime (struct tm *tmptr); struct tm { /* a broken-down time */ int tm_sec; /* seconds after the minute: [0 - 60] */ int tm_min; /* minutes after the hour: [0

C中获取当前时间的函数

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突然要用到C程序里调用当前时间，来测试一段代码的运行时间。找了一下是否有可以调用的库函数，没想到真的有：gettimeofday。因为这里的这个应用蛮常用的，所以留个记录在此。 1 #include < stdio.h > 2 #include < stdlib.h > 3 4 struct timeval 5 { 6 long tv_sec; /* 秒数 */ 7 long tv_usec; /* 微秒数 */ 8 }; 9 10 struct timezone 11 { 12 int tv_minuteswest; 13 int tv_dsttime; 14 }; 15 16 int gettimeofday( struct timeval * tv, struct timezone * tz); 17 18 void function() 19 { 20 // function to run some time consuming codes 21 } 22 23 int main( int argc, char * argv[]) 24 { 25 struct timeval tpstart,tpend; 26 float timespend; 27 28 gettimeofday( & tpstart,NULL); 29 function(); 30

Strange errors using timeval struct and gettimeofday —because of semicolon in #define

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问题 I am getting a couple of weird compilation errors. This is for a homework assignment (help is ok). The idea is to implement a program that tests how well the user can hit "enter" once a second. I'm supposed to use gettimeofday to get some time values for each "enter" and then find out what the average time is and standard deviation... I'm trying to do this by checking stdin for '\n' and then if true, using gettimeofday to populate a timeval struct, then store said struct in an array for later

How to subtract two gettimeofday instances?

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问题 I want to subtract two gettimeofday instances, and present the answer in milliseconds. The idea is: static struct timeval tv; gettimeofday(&tv, NULL); static struct timeval tv2; gettimeofday(&tv2, NULL); static struct timeval tv3=tv2-tv; and then convert 'tv3' into milliseconds resolution. 回答1: You can use the timersub() function provided by glibc, then convert the result to milliseconds (watch out for overflows when doing this, though!). 回答2: Here's how to do it manually (since timersub isn

What should I use to replace gettimeofday() on Windows?

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问题 I'm writing a portable Socket class that supports timeouts for both sending and receiving... To implement these timeouts I'm using select() .... But, I sometimes need to know how long I was blocked inside select() which of course on Linux I would implement by calling gettimeofday() before and after I call select() and then using timersub() to calculate the delta... Given that select() on Windows accepts struct timeval for it's timeout, what method should I used to replace gettimeofday() on

What should I use to replace gettimeofday() on Windows?

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how to use gettimeofday() or something equivalent with Visual Studio C++ 2008?

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问题 Could someone please help me to use gettimeofday() function with Visual Studio C++ 2008 on Windows XP? here is a code that I found somewhere on the net: #include < time.h > #include <windows.h> #if defined(_MSC_VER) || defined(_MSC_EXTENSIONS) #define DELTA_EPOCH_IN_MICROSECS 11644473600000000Ui64 #else #define DELTA_EPOCH_IN_MICROSECS 11644473600000000ULL #endif struct timezone { int tz_minuteswest; /* minutes W of Greenwich */ int tz_dsttime; /* type of dst correction */ }; int gettimeofday

时间获取函数封装--linux/unix

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> 项目开发中在提高程序效率时，首先要定位到代码那个部分耗费时间较长，进而改进代码--缩短执行时间。这就要一个时间获取函数来准确获取时间，在linux/unix系统都有对应的时间获取函数，不过要对其转换封装才可以得到我们想要且看得懂的数值，下例是以封装 gettimeofday()函数和 struct timeval结构体获取的时间获取函数。 #include <sys/time.h> #include <unistd.h> 定义函数：int gettimeofday (struct timeval * tv, struct timezone * tz); 函数说明：gettimeofday()会把目前的时间有tv 所指的结构返回，当地时区的信息则放到tz 所指的结构中。 timeval 结构定义为： struct timeval{ long tv_sec; //秒 long tv_usec; //微秒 }; timezone 结构定义为： struct timezone { int tz_minuteswest; //和Greenwich 时间差了多少分钟 int tz_dsttime; //日光节约时间的状态 }; 很多时候不要第二个参数值，所以一般都设置为‘NULL ’ //返回值是微妙单位 UB8 ldw

gettimeofday clock_gettime solution to generate unique number

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问题 My process runs multiple instances (processes) and multiple threads and all of them write to the same database. As soon as the request is placed, a unique req id is generated for the record to be added to the proprietary db. Here are our limitations: It cannot be more than 9 char length, needs to have hhmmss as the first 6 chars. We decided to use ms for the last 3 digits to complete the 9 chars and we are doing all this using gettimeofday() . However, with increased traffic, there are now