比较2个包含时间和日期的字符串

Question

I'm writing a C code and have a problem in comparing 2 variable containing time. The first time are acquired from a database which is in string format. The second date are to get the current local time. Since the first date is in string. I decide to make the second time also in string. The problem is how to compare the 2 variable to see which one is bigger or earlier? At first I tried strncmp. But then, that function check the size of the string. I tried to change the string into number format but still failed. My idea is to use difftime, but then again, my time is in string and not time_t format. Is it possible to change from string into time_t? Can anyone suggest a function that can help me do the operation?

I'm following this topic as a guidance. comparing two dates with different format in C

int seq_day(char *date) {
    int y = strtol(date, &date, 10);
    int m = strtol(++date, &date, 10);
    int d = strtol(++date, &date, 10);
    return (y*12+m)*31+d;
}

int expired_demotion_time()
{
    char current_datetime[50] = {0};
    int result1,result2;
    get_today_str(current_datetime, sizeof(current_datetime), "%Y-%m-%dT%H:%M:%S");
    printf("%s \n",current_datetime);
    printf("%s \n",selected_g->database_time);
    result1 = seq_day(current_datetime);
    result2 = seq_day(selected_g->database_time);
    printf("%d \n",result1);
    printf("%d \n",result2);
    if((result1==result2)||(result1>result2))
    {
            return 1;
    }
    return 0;

}

This is the output from my code.

2013-11-25T13:11:17  \\current date. I'm making this string to follow the exact way as the first string.
2013-11-25T13:17:43  \\demotion time. Please take note that I cannot change this since this is taken from database.
749202  \\somehow both of them produce the same number
749202

Answer 1

this is because your code ignores time values:

int seq_day(char *date) {
    int y = strtol(date, &date, 10);
    int m = strtol(++date, &date, 10);
    int d = strtol(++date, &date, 10);
    return (y*12+m)*31+d;
}

for pure C i think you're need to use sscanf function to parse string to set of integers, like this:

long seq_day(char *date) {
    int y,m,d,hh,mm,ss;
    sscanf("%d-%d-%dT%d:%d:%d",&y,&m,&d,&hh,&mm,&ss);
    return ((((y*12L+m)*31L+d)*24L+hh)*60L+mm)*60L+ss;
}