Get time in the Linux kernel and convert cost to timezone time

The following function, GET_TIME_STR, implements the ability to get local time in the kernel.

He first gets the UTC time and then translates the cost to time based on the system's time zone timezone,

The time is finally exported to the output buffer in the form of a string of "2014-11-02 21:14:08".

The return value of the function. Is the length of the output string.

#include <linux/time.h>

#include <linux/timex.h>

#include <linux/rtc.h>

int Get_time_str (char *output)
{
struct Timex Txc;
struct Rtc_time TM;

/* Gets the current UTC time */
Do_gettimeofday (& (Txc.time));

/* Adjust UTC time to local time */
TXC.TIME.TV_SEC-= sys_tz.tz_minuteswest * 60;

/* Calculate the number of months and days in the time to the TM */
Rtc_time_to_tm (TXC.TIME.TV_SEC,&TM);

return sprintf (Output, "%04d-%02d-%02d%02d:%02d:%02d"
, tm.tm_year+1900
, tm.tm_mon+1
, Tm.tm_mday
, Tm.tm_hour
, Tm.tm_min
, tm.tm_sec);
}

In fact. The system call Gettimeofday is implemented by Sys_gettimeofday ().

Sys_gettimeofday () is simply a copy of the time value obtained from the call to Do_gettimeofday () to the user state.

Its code such as the following:

Asmlinkage long sys_gettimeofday (struct timeval __user *tv, struct timezone __user *tz)
{
if (likely (TV! = NULL)) {
struct Timeval KTV;
Do_gettimeofday (&KTV);
if (Copy_to_user (TV, &ktv, sizeof (KTV)))
Return-efault;
}


if (unlikely (tz! = NULL)) {
if (Copy_to_user (TZ, &sys_tz, sizeof (SYS_TZ)))
Return-efault;
}
return 0;
}

Get time in the Linux kernel and convert cost to timezone time