Getting system uptime in iOS/Swift

Question

Is there a way to get system uptime in iOS (using Swift)? What I need is to measure time without having to worry about the user changing the time. In Android there's a elapsedCurrentTimeMillis() that returns the number of milliseconds since boot, but now I need something like that for iOS. There's an accepted answer here Getting iOS system uptime, that doesn't pause when asleep but that's for Objective C and I need it for Swift and I don't know how to convert it.

That doesn't take into account sleep time. I need a way to reliably measure how much time has passed, even if the app is shut down in the meantime and even if the user changes the time. — TimSim, Mar 24 '16 at 16:11

score 16 · Accepted Answer · edited May 23 '17 at 10:30

16

As you ask for a pure-Swift solution, I converted the ObjC code from the answer you mentioned Getting iOS system uptime, that doesn't pause when asleep.

func uptime() -> time_t {
    var boottime = timeval()
    var mib: [Int32] = [CTL_KERN, KERN_BOOTTIME]
    var size = strideof(timeval)

    var now = time_t()
    var uptime: time_t = -1

    time(&now)
    if (sysctl(&mib, 2, &boottime, &size, nil, 0) != -1 && boottime.tv_sec != 0) {
        uptime = now - boottime.tv_sec
    }
    return uptime
}

// print(uptime())

To make it a bit prettier, we can use sysctlbyname instead of sysctl:

// var mib: [Int32] = [CTL_KERN, KERN_BOOTTIME]
sysctlbyname("kern.boottime", &boottime, &size, nil, 0)

edited May 23 '17 at 10:30

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answered Mar 24 '16 at 16:00

Donghua Li

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2
9

2

@JAL I debugged and figured out the different behaviour of sizeof between ObjC and Swift. It works now! – Donghua Li Mar 24 '16 at 16:20
Yup, this works, shows the same value as Objective-C code version! And I can see I'm going to have a hard time programming... – TimSim Mar 24 '16 at 16:30
2

i get a `Use of unresolved identifier 'strideof'` error in swift 5. looks like the syntax changed but i am not sure what to – Anushk May 23 '20 at 08:21
2

@Anushk replace `strideof(timeval)` with `MemoryLayout.stride` – Sam Nov 07 '20 at 23:42

score 6 · Answer 2 · answered Nov 30 '17 at 02:30

6

This is a solution in Swift 4.

 var boottime = timeval()
 var size = MemoryLayout<timeval>.stride
 sysctlbyname("kern.boottime", &boottime, &size, nil, 0)

answered Nov 30 '17 at 02:30

Anthony Kong

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score 6 · Answer 3 · answered Jul 23 '19 at 18:21

Updated for Swift 5 and straight from ADF post here:

func bootTime() -> Date? {  
    var tv = timeval()  
    var tvSize = MemoryLayout<timeval>.size  
    let err = sysctlbyname("kern.boottime", &tv, &tvSize, nil, 0);  
    guard err == 0, tvSize == MemoryLayout<timeval>.size else {  
        return nil  
    }  
    return Date(timeIntervalSince1970: Double(tv.tv_sec) + Double(tv.tv_usec) / 1_000_000.0)  
}

"Be aware that this time will change if the system clock changes, that is, the value is the boot time relative to the current system clock."

What's the point of boot time that depends on the system clock changes? Did they change this behavior or what? — TimSim, Jul 29 '20 at 16:48

score 2 · Answer 4 · edited May 23 '17 at 11:47

2

You can call ObjC code from Swift:

print(SystemUtil().uptime());

Write a ObjC class like the accepted answer you mentioned: Getting iOS system uptime, that doesn't pause when asleep.

SystemUtil.h for interface:

#import <Foundation/Foundation.h>

@interface SystemUtil : NSObject

- (time_t)uptime;

@end

SystemUtil.m for implementation:

#import "SystemUtil.h"
#include <sys/sysctl.h>

@implementation SystemUtil

- (time_t)uptime
{
    struct timeval boottime;
    int mib[2] = {CTL_KERN, KERN_BOOTTIME};
    size_t size = sizeof(boottime);
    time_t now;
    time_t uptime = -1;

    (void)time(&now);

    if (sysctl(mib, 2, &boottime, &size, NULL, 0) != -1 && boottime.tv_sec != 0) {
        uptime = now - boottime.tv_sec;
    }
    return uptime;
}

@end

And don't forget to include a <Project>-Bridge-Header.h with the following content so that you can use the ObjC class from Swift (<Project> is your project name):

#import "SystemUtil.h"

edited May 23 '17 at 11:47

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answered Mar 24 '16 at 15:31

Donghua Li

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9

The OP is asking for a native Swift solution. – JAL Mar 24 '16 at 15:40
This works. I think. It's showing plausible non-zero uptime. For anyone as dumb as me, all you need to do is create the .h and .m files in Xcode (File->New->File...->iOS->Source) and put in them what @donghua-li wrote, and Bridge-Header.h will be automatically created (so just add the #import) – TimSim Mar 24 '16 at 16:24
@TimSim I've worked out a [pure-Swift solution](http://stackoverflow.com/a/36204651/4912403). – Donghua Li Mar 24 '16 at 16:31

Getting system uptime in iOS/Swift

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