how to get timestamp in c

Question

I want to get timestamp for my log in c. i have written a function to get timestamp. But when i return the variable i m getting different value.

My code:

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Answer 1

In answering this question I wanted a function that was simple, thread friendly, did not return a char* (which is often tedious to manage), thread-safe and could stand on its own feet. I have an aversion to functions that return char* or pointers that must be managed.

The function below does not call malloc.

The function takes no parameters and returns a timestamp. I think it works well.

struct Timestamp {
    time_t seconds;
    long milliseconds;
    char timestring[32];
};


struct Timestamp getTimestamp()
{
char   timebuffer[32]     = {0};
struct timeval  tv        = {0};
struct tm      *tmval     = NULL;
struct tm       gmtval    = {0};
struct timespec curtime   = {0};

struct Timestamp timestamp;

int i = 0;

// Get current time
clock_gettime(CLOCK_REALTIME, &curtime);


// Set the fields
timestamp.seconds      = curtime.tv_sec;
timestamp.milliseconds = round(curtime.tv_nsec/1.0e6);

if((tmval = gmtime_r(×tamp.seconds, &gmtval)) != NULL)
{
    // Build the first part of the time
    strftime(timebuffer, sizeof timebuffer, "%Y-%m-%d %H:%M:%S", &gmtval);

    // Add the milliseconds part and build the time string
    snprintf(timestamp.timestring, sizeof timestamp.timestring, "%s.%03ld", timebuffer, timestamp.milliseconds); 
}

return timestamp;
}

int main()
{
    char   timebuffer[64]     = {0};
    int i = 0;
    struct timespec sleeptime = {0, 5000000L};

    struct Timestamp timestamp;

    for (i=0; i < 20; i++)
    {
        timestamp = getTimestamp();
        printf("Time is: %s \n", timestamp.timestring);
        nanosleep(&sleeptime, NULL);
    }

    return 0;
}