Get system installation date programmatically - macos

Question

I am trying to get the system installation date by running a console app.
The only way I know how to do this is by parsing the /var/log/install.log file for the latest string containing OSInstaller & Install Complete items.
Is there a handy system API I am missing?

Answer 1

As a suggestion for exploration only:
You could try looking at the files /System/Library/Receipts.
You will probably see a com.apple.pkg.BaseSystemResources.plist file, its modification date may tell you when the OS was installed.
There are also com.apple.pkg.update.os.*.plist files for updates, again look at the modification dates and maybe parse the wildcard (*) bit if you can determined a naming convention.
HTH, Happy Hunting!

Answer 2

So in case, someone finds this useful.
Swift 3.0
SOLUTION 1
Initially I parsed /var/log/install.log file to get date string:
// To get OS installation date we'll need to check system log file and find entry which contains installation date
var systemDates : String? = nil
do {
let fullSystemLog = try NSString(contentsOf: URL(fileURLWithPath: "/var/log/install.log"), encoding: String.Encoding.utf8.rawValue)
let entries = fullSystemLog.components(separatedBy: "\n")
//Filter to get only entries about OS installation
let filtered = entries.filter{ entry in
return entry.contains("OSInstaller") && entry.contains("Install Complete") //Markers telling that OS was installed
}
var latestMention = ""
if filtered.count > 0 {
//If 1 or more entries found we'll pick last one
latestMention = filtered.last!
}
else if entries.count > 0 {
//If there are 0 mentions of OS installation - we'll use first entry in logs
latestMention = entries.first!
}
//parse picked entry for date
do {
let regex = try NSRegularExpression(pattern: ".+:[0-9]{2}", options: [])
let nsString = latestMention as NSString
let results = regex.matches(in: latestMention,
options: [], range: NSMakeRange(0, nsString.length))
let actualDateSubstrings = results.map { nsString.substring(with: $0.range)}
if let dateStringFromMention = actualDateSubstrings.first {
systemDates = dateStringFromMention
}
else {
systemDates = "<Error: no date results>"
}
} catch let error as NSError {
systemDates = "<Error: invalid regex: \(error.localizedDescription)>"
}
}
catch {
systemDates = "<Error: system log file not found>"
}
print("\tSYSTEM INSTALLED: \(systemDates)")
SOLUTION 2
The second solution appears much simpler. Look into the InstallDate field of /System/Library/Receipts/com.apple.pkg.BaseSystemResources.plist:
let systemDates = NSDictionary(contentsOfFile: "/System/Library/Receipts/com.apple.pkg.BaseSystemResources.plist")
print("\tSYSTEM INSTALLED: \(systemDates?["InstallDate"])")