linux C用strftime strptime将字符串与struct tm互转

参考摘自：https://bbs.csdn.net/topics/390674012 

linux C中

 

strftime将struct tm转换为字符串：

 

NAME
       strftime - format date and time

SYNOPSIS
       #include <time.h>

       size_t strftime(char *s, size_t max, const char *format, const struct tm *tm);

DESCRIPTION
       The  strftime()  function formats the broken-down time tm according to the format specification format
       and places the result in the character array s of size max.

RETURN VALUE
       Provided that the result string, including the terminating null byte, does not exceed max bytes, strf\u2010
       time() returns the number of bytes (excluding the terminating null byte) placed in the  array  s.   If
       the  length  of  the  result string (including the terminating null byte) would exceed max bytes, then
       strftime() returns 0, and the contents of the array are undefined.  (This behavior  applies  since  at
       least libc 4.4.4; very old versions of libc, such as libc 4.4.1, would return max if the array was too
       small.)

       Note that the return value 0 does not necessarily indicate an error.  For example, in many locales  %p
       yields an empty string.  An empty format string will likewise yield an empty string.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

 

  

strptime将字符串转换为struct tm;

NAME
       strptime - convert a string representation of time to a time tm structure

SYNOPSIS
       #define _XOPEN_SOURCE       /* See feature_test_macros(7) */
       #include <time.h>

       char *strptime(const char *s, const char *format, struct tm *tm);

DESCRIPTION
       The  strptime()  function  is  the  converse function to strftime(3) and converts the character string
       pointed to by s to values which are stored in the tm structure pointed to  by  tm,  using  the  format
       specified  by  format.  

RETURN VALUE
       The return value of the function is a pointer to the first character not processed  in  this  function
       call.  In case the input string contains more characters than required by the format string the return
       value points right after the last consumed input character.  In case the whole input  string  is  con\u2010
       sumed the return value points to the null byte at the end of the string.  If strptime() fails to match
       all of the format string and therefore an error occurred the function returns NULL.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

 

实例1：strftime()

#include <time.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include "time.h"

static char local_time[32] = {0};

char * my_get_time(void)
{
        time_t t_time;
        struct tm *t_tm;

        t_time = time(NULL);
        t_tm = localtime(&t_time);
        if (t_tm == NULL)
                return NULL;

        //if(strftime(local_time, sizeof(local_time), "%FT%T%z", t_tm) == 0) // 2020-01-08T09:28:54+0800
        //if(strftime(local_time, sizeof(local_time), "%FT%T", t_tm) == 0)   // 2020-01-08T09:30:27
        //if(strftime(local_time, sizeof(local_time), "%F", t_tm) == 0)      // 2020-01-08
        if(strftime(local_time, sizeof(local_time), "%T", t_tm) == 0)        // 09:32:40
                return NULL;
    
        return local_time;
}

int main(int argc, char *argv[])
{
        printf("%s\r\n", my_get_time());

        return 0;
}

 

实例2：strptime()

如下代码我是求两个时间的秒数

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

int main(int argc, char *argv[])
{
        //char fmt[] = "%Y-%m-%d %H:%M:%S";
        char fmt[] = "%F %T";
        time_t ggtime,curtime;
        struct tm *tb = (struct tm*)malloc(sizeof(struct tm));

        strptime(argv[1], fmt, tb);
        ggtime = mktime(tb);

        curtime = time(NULL);
        printf("The pause used %f seconds.\n",difftime(curtime,ggtime));

        return 0;
}

 

 

运行：
[root@localhost 05]# ./main  '2020-1-8 10:00:02'
The pause used 25.000000 seconds.