问题描述

我在 stackoverflow 网站上查看了我的答案，我没有得到，所以我把它贴在这里.

I checked the stackoverflow site for my answer, i did not get, so i am posting it here.

我的问题是:

如何比较格式"Month Date hh:mm:ss"的两个时间戳?

How to compare two time stamp in format "Month Date hh:mm:ss"?

我正在用 C 和 C++ 编写程序，时间是可显示的字符串格式.

I am writing program in C and C++ and the time is in displayable string format.

示例:

time1 = "Mar 21 11:51:20"
time2 = "Mar 21 10:20:05"

我想比较 time1 和 tme2 并找出 time2 是否是 after time1 并且我需要输出为 true 或 false，如下所示:

I want to compare time1 and tme2 and find out whether time2 is after time1 or not and I need output as true or false, like below:

 if time2 > time1 then 
       i need output as 1 
 or 
       0 or -1 anything

我使用了 difftime(time2,time1) ，但它返回 time1 和 time2 之间的增量时间 diff>.
我想检查是否更大.

I used difftime(time2,time1) , but it returns the delta time diff between time1 and time2.
I want to check greater or not.

如有任何帮助，提前致谢

For any help, thanks in advance

推荐答案

FIRST-使用difftime进行比较:

FIRST- use difftime to compare:

你可以简单地使用 difftime()比较时间并返回1或-1的函数如下:

you can simply use difftime() function to compare time and return 1 or -1 as follows:

int comparetime(time_t time1,time_t time2){
 return difftime(time1,time2) > 0.0 ? 1 : -1; 
} 

SECOND- 将字符串转换为时间:

SECOND- Convert string into time:

如果你转换 string 转化为 time_t结构有困难，你可以依次使用两个函数:

If you have difficulty to convert string into time_t struct, you can use two functions in sequence:

1. char *strptime(const char *buf, const char *format, struct tm *tm); 函数.将字符串转换为 struct tm

示例:将日期时间字符串 "Mar 21 11:51:20 AM" 转换为 struct tm 您需要三个格式化字符串:

Example: to convert date-time string "Mar 21 11:51:20 AM" into struct tm you need three formate strings:

%b :月份名称，可以是全名或缩写
%d:月中的第几天 [1–31].
%r :区域设置的 AM/PM 格式的时间.如果在本地时间格式中不可用，则默认为 POSIX 时间 AM/PM 格式:%I:%M:%S %p.

%b : Month name, can be either the full name or an abbreviation
%d : Day of the month [1–31].
%r : Time in AM/PM format of the locale. If not available in the locale time format, defaults to the POSIX time AM/PM format: %I:%M:%S %p.

#include <stdio.h>
#include <time.h>
int main(void){
    time_t t1, t2;
    struct tm *timeptr,tm1, tm2;
    char* time1 = "Mar 21 11:51:20 AM";
    char* time2 = "Mar 21 10:20:05 AM";

    //(1) convert `String to tm`:  
    if(strptime(time1, "%b %d %r",&tm1) == NULL)
            printf("
strptime failed
");          
    if(strptime(time2, "%b %d %r",&tm2) == NULL)
            printf("
strptime failed
");

    //(2)   convert `tm to time_t`:    
    t1 = mktime(&tm1);
    t2 = mktime(&tm2);  

     printf("
 t1 > t2 : %d", comparetime(t1, t2));
     printf("
 t2 > t1 : %d", comparetime(t2, t1));
     printf("
");
     return 1;
}

 $ ./a.out 
 t1 > t2 : 1
 t2 > t1 : -1