Programmatically Screenshot | Swift 3, macOS

let displayID = CGMainDisplayID()
let imageRef = CGDisplayCreateImage(displayID)

Yes its possible. This function takes all connected monitors screenshots and writes to specified path as jpg file. Generates file name as unix time stamp.

 func TakeScreensShots(folderName: String){
    
    var displayCount: UInt32 = 0;
    var result = CGGetActiveDisplayList(0, nil, &displayCount)
    if (result != CGError.success) {
        print("error: \(result)")
        return
    }
    let allocated = Int(displayCount)
    let activeDisplays = UnsafeMutablePointer<CGDirectDisplayID>.allocate(capacity: allocated)
    result = CGGetActiveDisplayList(displayCount, activeDisplays, &displayCount)
    
    if (result != CGError.success) {
        print("error: \(result)")
        return
    }
       
    for i in 1...displayCount {
        let unixTimestamp = CreateTimeStamp()
        let fileUrl = URL(fileURLWithPath: folderName + "\(unixTimestamp)" + "_" + "\(i)" + ".jpg", isDirectory: true)
        let screenShot:CGImage = CGDisplayCreateImage(activeDisplays[Int(i-1)])!
        let bitmapRep = NSBitmapImageRep(cgImage: screenShot)
        let jpegData = bitmapRep.representation(using: NSBitmapImageRep.FileType.jpeg, properties: [:])!
        
        
        do {
            try jpegData.write(to: fileUrl, options: .atomic)
        }
        catch {print("error: \(error)")}
    }
}

func CreateTimeStamp() -> Int32
{
    return Int32(Date().timeIntervalSince1970)
}