Get the boot time in objective c

问题:

how can i get the boot time of ios in objective c ?

Is there a way to get it?

回答1:

Don't know if this will work in iOS, but in OS X (which is essentially the same OS) you would use sysctl(). This is how the OS X Unix utility uptime does it. Source code is available - search for "boottime".

#include <sys/types.h>
#include <sys/sysctl.h>  

// ....  

#define MIB_SIZE 2  

int mib[MIB_SIZE];
size_t size;
struct timeval  boottime;

mib[0] = CTL_KERN;
mib[1] = KERN_BOOTTIME;
size = sizeof(boottime);
if (sysctl(mib, MIB_SIZE, &boottime, &size, NULL, 0) != -1)
{
    // successful call
    NSDate* bootDate = [NSDate dateWithTimeIntervalSince1970:boottime.tv_sec];
}

The restricted nature of programming in the iOS sandboxed environment might make it not work, I don't know, I haven't tried it.

回答2:

I took JeremyP's answer, gave the result the full microsecond precision, clarified the names of local variables, improved the order, and put it into a method:

#include <sys/types.h>
#include <sys/sysctl.h>  

// ....  

+ (nullable NSDate *)bootDate
{
    // nameIntArray and nameIntArrayLen
    int nameIntArrayLen = 2;
    int nameIntArray[nameIntArrayLen];
    nameIntArray[0] = CTL_KERN;
    nameIntArray[1] = KERN_BOOTTIME;

    // boot_timeval
    struct timeval boot_timeval;
    size_t boot_timeval_size = sizeof(boot_timeval);
    if (sysctl(nameIntArray, nameIntArrayLen, &boot_timeval, &boot_timeval_size, NULL, 0) == -1)
    {
        return nil;
    }

    // bootSince1970TimeInterval
    NSTimeInterval bootSince1970TimeInterval = (NSTimeInterval)boot_timeval.tv_sec + ((NSTimeInterval)boot_timeval.tv_usec / 1000000);

    // return
    return [NSDate dateWithTimeIntervalSince1970:bootSince1970TimeInterval];
}