Retrieve Linux Time using struct timespec

Question

Can someone please suggest how can I retrieve linux time using

struct timespec ts

type? It just gives me time since Epoch. Can I get the actual Linux time using this datatype?

Brief Background: I am writing a logger utility on embedded device with timestamp resolution in milli/micro seconds. The source adds timestamp which is consumed by destination component.

struct stLogItem logitem; //stLogItem has a member, struct timespec ts    
clock_gettime(clk_id, &logitem.ts);

The destination component is printing this log timestamp on file/console. But the date which is printed out is time since Epoch, and not the actual Linux date.

The printed data is: 1970-01-01 23:30:07.586864475

Whereas, the Linux date is different as shown below:

root@imh:# date

Tue Nov 14 11:34:12 UTC 2017

Its not a format issue. It is about getting the current Linux time (in nano seconds).

Answer 1

After calling clock_gettime, ts.tv_sec, which has type time_t, is populated with the timestamp in seconds since the epoch. You can pass that directly to localtime:

struct timespec ts;    
clock_gettime(clk_id, &ts);
struct tm *my_tm = localtime(&ts.tv_sec);

Now my_tm points to a struct tm which has the time broken down into year / month / day / hour / minute / second, and ts.tv_nsec has the nanosecond portion.