real_uptime_ns.py

def real_uptime_ns():
    from time import CLOCK_BOOTTIME
    from time import clock_gettime_ns
    from os import sysconf, sysconf_names

    with open("/proc/self/stat") as f:
        stat_fields = f.readline().split()
        proc_start_since_boot_tick = float(stat_fields[21])
        start_since_boot_sec = proc_start_since_boot_tick / sysconf(
            sysconf_names["SC_CLK_TCK"]
        )

    return clock_gettime_ns(CLOCK_BOOTTIME) - int(start_since_boot_sec * 1_000_000_000)


def human_ns(time_ns_val):
    if time_ns_val >= 60_000_000_000:
        return "{:.1f}m".format(time_ns_val / 60_000_000_000)
    elif time_ns_val >= 1_000_000_000:
        return "{:.3f}s".format(time_ns_val / 1_000_000_000)
    elif time_ns_val >= 1_000_000:
        return "{:.1f}ms".format(time_ns_val / 1_000_000)
    else:
        return "{}ns".format(time_ns_val)


if __name__ == "__main__":
    from time import sleep
    from sys import stdout
    import os

    sleep(0.542)
    stdout.write("real_uptime_ns: {}\n".format(human_ns(real_uptime_ns())))
    getattr(os, "_exit")(0)  # exit as soon as possible