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Equivalent to GetTickCount() on Linux

Posted by: admin November 29, 2017 Leave a comment

Questions:

I’m looking for an equivalent to GetTickCount() on Linux.

Presently I am using Python’s time.time() which presumably calls through to gettimeofday(). My concern is that the time returned (the unix epoch), may change erratically if the clock is messed with, such as by NTP. A simple process or system wall time, that only increases positively at a constant rate would suffice.

Does any such time function in C or Python exist?

Answers:

You can use CLOCK_MONOTONIC e.g. in C:

struct timespec ts;
if(clock_gettime(CLOCK_MONOTONIC,&ts) != 0) {
 //error
}

See this question for a Python way – How do I get monotonic time durations in python?

Questions:
Answers:

This seems to work:

#include <unistd.h>
#include <time.h>

uint32_t getTick() {
    struct timespec ts;
    unsigned theTick = 0U;
    clock_gettime( CLOCK_REALTIME, &ts );
    theTick  = ts.tv_nsec / 1000000;
    theTick += ts.tv_sec * 1000;
    return theTick;
}

yes, get_tick()
Is the backbone of my applications.
Consisting of one state machine for each ‘task’
eg, can multi-task without using threads and Inter Process Communication
Can implement non-blocking delays.

Questions:
Answers:

You should use: clock_gettime(CLOCK_MONOTONIC, &tp);. This call is not affected by the adjustment of the system time just like GetTickCount() on Windows.

Questions:
Answers:

Yes, the kernel has high-resolution timers but it is differently. I would recommend that you look at the sources of any odd project that wraps this in a portable manner.

From C/C++ I usually #ifdef this and use gettimeofday() on Linux which gives me microsecond resolution. I often add this as a fraction to the seconds since epoch I also receive giving me a double.