C:gettimeofday()每次运行都会产生相同的值

Question

我正在尝试以秒精度打印ISO-8601中的时间.YYYY-MM-DDTHH:MM:SS.S

这是我的代码:

#include <sys/time.h>
#include <time.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>

void milli_time(char* dest, struct timeval* t)
{
    struct tm* timeInfo;
    strftime(dest, 22, "%Y-%m-%dT%t", localtime(&t->tv_sec));
    printf("%s\n", dest);
    fflush(stdout);
    char deciTime[3];
    sprintf(deciTime, ".%lu", ((t->tv_usec)/100000ul));

    strcat(dest, deciTime);
}

int main()
{
    struct timeval* theTime;
    char timeString[32];
    gettimeofday(theTime, NULL);
    printf("%lu.%lu\n", theTime->tv_sec, theTime->tv_usec);
    milli_time(timeString, theTime);
    printf("%s\n", timeString);
    fflush(stdout);
}

每次运行它的输出是:

134520616.3077826840
1974-04-06T17:50:16
1974-04-06T17:50:16.30778

我注意到的另一件事是tv_usec超过一百万.

Answer 1

更改struct timeval* theTime到struct timeval theTime和更新它的相应的参考:

gettimeofday(&theTime, NULL);
// etc

这样您就可以为结构分配空间,而不仅仅是指向结构的指针.当我尝试在我的机器上运行它时,您的代码会出现段错误.