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@igrr
Last active April 11, 2023 09:44
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#include <stdio.h>
#include <time.h>
#include <sys/time.h>
#include <unistd.h>
static void set_time(void);
static void get_time(void);
void app_main(void)
{
set_time();
while (1) {
get_time();
sleep(1);
}
}
static void set_time(void)
{
// Prepare the broken-down time.
// See https://en.cppreference.com/w/c/chrono/tm
struct tm initial_time = {
.tm_year = 2022 - 1900,
.tm_mon = 3 - 1,
.tm_mday = 17 - 1,
.tm_hour = 21,
.tm_min = 35,
.tm_sec = 0
};
// Convert to Unix time.
// See https://en.cppreference.com/w/c/chrono/mktime
time_t initial_unix_time = mktime(&initial_time);
// Convert to 'struct timeval'
struct timeval initial_timeval = {
.tv_sec = initial_unix_time,
.tv_usec = 0
};
// Set system time.
// See https://linux.die.net/man/2/settimeofday
int err = settimeofday(&initial_timeval, NULL);
assert(err == 0);
printf("Time set to: %s", asctime(&initial_time));
}
static void get_time(void)
{
// Get current time as 'struct timeval'.
// See https://linux.die.net/man/2/gettimeofday
struct timeval new_timeval;
int err = gettimeofday(&new_timeval, NULL);
assert(err == 0);
// Extract Unix time
time_t new_unix_time = new_timeval.tv_sec;
// Convert to broken-down time
// See https://en.cppreference.com/w/c/chrono/localtime
struct tm new_time;
localtime_r(&new_unix_time, &new_time);
// 'new_time' now contains the current time components
printf("Current time: %s", asctime(&new_time));
}
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