更正 C 代码日志文件上的时间戳

Question

>我目前正在用DHT11温度和湿度传感器和LCD显示屏对我的Raspberry Pi（B型）进行编程。我编写了一个 C 脚本，将从温度传感器获得的值记录到状态文件中，然后将其添加到日志文件中。脚本如下：

#include <time.h>
#define LOGFILE "/var/log/temp.log"
#define CURRENTFILE "/var/temp.data"

/* Saves the date time and humidity to a log file and current file */

void write_value (int temp, int humidity) {
    time_t current_time;
    current_time = time(NULL);
    /* Write to log file */
    FILE *logfd;
    logfd = fopen (LOGFILE, "a");
    fprintf (logfd, "%ld %d %dn", current_time, temp, humidity);
    fclose (logfd);
    /* Write to current file */
    FILE *currfd;
    currfd = fopen(CURRENTFILE, "w");
    fprintf (currfd, "%ld %d %dn", current_time, temp, humidity);
    fclose (currfd); 
}

但是，它可以工作;我在日志文件中获得的输出如下：

1428539174 16 41
1428539232 17 40
1428539257 18 40
1428539304 19 39
1428539319 19 39

第一行旨在作为日期和时间戳，温度和湿度。

您对我如何修复日期和时间以及将其更改为DD/MM/YYYY HH：MM：SS（日/月/年小时：分钟：秒）格式有什么建议吗？

根据@pmg的建议，脚本更改为：

#include <time.h>
#define LOGFILE "/var/log/temp.log"
#define CURRENTFILE "/var/temp.data"

/* Saves the date time and humidity to a log file and current file */

void write_value (int temp, int humidity) {
    char dt[20]; // space enough for YYYY-MM-DD HH:MM:SS and terminator
    struct tm tm;
    time_t current_time;
    current_time = time(NULL);
    tm = *localtime(&current_time); // convert time_t to struct tm
    strftime(dt, sizeof dt, "%Y-%m-%d %H:%M:%S", &tm); // format
    /* Write to log file */
    FILE *logfd;
    logfd = fopen (LOGFILE, "a");
    fprintf (logfd, "%s %d %d/n", dt, temp, humidity);
    fclose (logfd);
    /* Write to current file */
    FILE *currfd;
    currfd = fopen(CURRENTFILE, "w");
    fprintf (currfd, "%s %d %d/n", dt, temp, humidity);
    fclose (currfd); 
}

Answer 1

将time_t值转换为struct tm，然后适当地设置格式

char dt[20]; // space enough for DD/MM/YYYY HH:MM:SS and terminator
struct tm tm;
time_t current_time;
current_time = time(NULL);
tm = *localtime(&current_time); // convert time_t to struct tm
strftime(dt, sizeof dt, "%d/%m/%Y %H:%M:%S", &tm); // format
fprintf(currfd, "%s %d %dn", dt, temp, humidity);

请参阅localtime()和strftime()的POSIX描述。