Using sysctlbyname() from Swift

Question

I’m using the code from this Gist to determine which iOS device (e.g. iPhone5,1) my app is running on:

- (NSString *)platform
{
    size_t size;
    sysctlbyname("hw.machine", NULL, &size, NULL, 0);
    char *machine = malloc(size);
    sysctlbyname("hw.machine", machine, &size, NULL, 0);
    NSString *platform = [NSString stringWithUTF8String:machine];
    free(machine);
    return platform;
}

The Swift documentation indicates that C data types are well-supported, but it doesn’t say anything about C functions. Is there a pure Swift way to retrieve the machine identifier, or will I have to bridge into Objective-C for this?

Answer 1

You can do the same in Swift (error checking omitted for brevity):

func platform() -> String {
    var size : Int = 0 // as Ben Stahl noticed in his answer
    sysctlbyname("hw.machine", nil, &size, nil, 0)
    var machine = [CChar](count: size, repeatedValue: 0)
    sysctlbyname("hw.machine", &machine, &size, nil, 0)
    return String.fromCString(machine)!
}

Update for Swift 3:

func platform() -> String {
    var size = 0
    sysctlbyname("hw.machine", nil, &size, nil, 0)
    var machine = [CChar](repeating: 0,  count: size)
    sysctlbyname("hw.machine", &machine, &size, nil, 0)
    return String(cString: machine)
}

Update for Swift 6:

String(cString:) is now deprecated, attribution goes to https://stackoverflow.com/a/79423711/1187415 .

func platform() -> String? {
    var size = 0
    if sysctlbyname("hw.machine", nil, &size, nil, 0) != 0 {
        return nil
    }
    var machine = [CChar](repeating: 0,  count: size)
    if sysctlbyname("hw.machine", &machine, &size, nil, 0) != 0 {
        return nil
    }
    return String(utf8String: machine)
}