Home »c »time »gmtime_r

struct tm *gmtime_r(time_t *timep, struct tm *result)

The gmtime_r() is similar to gmtime(), but stores data in user supplied struct.

Examples

1. current time around the world
2. use gmtime_r() in a multithreading enviroment

current time around the world   return

program.c   copy

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#include <stdio.h>

#include <time.h>

 

void print_time(struct tm *tm,const char *location, intzone)

{

    inthour;

 

    hour = (24 +tm->tm_hour + zone) % 24;

    printf("%20s: %02d:%02d\n", location, hour,tm->tm_min);

}

 

// Mountain Standard Time (MST) is 7 hours behind Coordinated Universal Time.

#define MST -7

 

// Greenwich Mean Time (GMT) has no offset from Coordinated Universal Time.

#define GMT 0

 

// China Standard Time (CST) is 8 hours ahead of Coordinated Universal Time.

#define CST 8

 

int main()

{

    time_tnow;

    structtm tm;

 

    now =time(NULL);

    // convert 'struct tm' to 'time_t'

    gmtime_r(&now, &tm);

 

    print_time(&tm,"Phoenix, USA", MST);

    print_time(&tm,"London, England", GMT);

    print_time(&tm,"Beijing, China", CST);

    return0;

}

Output

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   Phoenix, USA: 05:38

London, England: 12:38

 Beijing, China: 20:38

use gmtime_r() in a multithreading enviroment   return

program.c   copy

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#include <stdio.h>

#include <pthread.h>

#include <time.h>

#include <unistd.h>

 

void print_time()

{

    time_tnow;

    structtm tm;

    charbuffer[64];

 

    now =time(NULL);

    gmtime_r(&now, &tm);

    asctime_r(&tm, buffer);

    printf("UTC time = %s", buffer);

}

 

void*routine(void*arg)

{

    inti;

 

    for(i = 0; i < 2; i++) {

        print_time();

        sleep(1);

    }

    returnNULL;

}

 

int main()

{

    inti;

    pthread_t tid;

 

    pthread_create(&tid, NULL, routine, NULL);

    routine(NULL);

    pthread_join(tid, NULL);

    return0;

}

Output

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UTC time= Fri Jan  2 12:43:08 2015

UTC time= Fri Jan  2 12:43:08 2015

UTC time= Fri Jan  2 12:43:09 2015

UTC time= Fri Jan  2 12:43:09 2015