Get boot time and uptime for macOS & iOS.

Uptime.swift

// https://stackoverflow.com/a/45068046/5536516

import Foundation

func kernelBootTime() -> timeval {

    var mib = [ CTL_KERN, KERN_BOOTTIME ]
    var bootTime = timeval()
    var bootTimeSize = MemoryLayout<timeval>.size

    if 0 != sysctl(&mib, UInt32(mib.count), &bootTime, &bootTimeSize, nil, 0) {
        fatalError("Could not get boot time, errno: \(errno)")
    }

    return bootTime
}

func uptime() -> timespec {

    var uptime = timespec()
    if 0 != clock_gettime(CLOCK_MONOTONIC_RAW, &uptime) {
        fatalError("Could not execute clock_gettime, errno: \(errno)")
    }

    return uptime
}

print(kernelBootTime()) // timeval(tv_sec: 1499259206, tv_usec: 122778)
print(uptime()) // timespec(tv_sec: 636705, tv_nsec: 750700397)