Swift start Process and read continously changed output - swift

Question

I have this code to continously read the output of a started process:
let task = Process()
task.arguments = ["-c", command]
task.launchPath = "/bin/zsh"
let pipe = Pipe()
let errorPipe = Pipe()
task.standardOutput = pipe
task.standardError = errorPipe
let outHandle = pipe.fileHandleForReading
let errorHandle = errorPipe.fileHandleForReading
outHandle.waitForDataInBackgroundAndNotify()
errorHandle.waitForDataInBackgroundAndNotify()
var updateObserver: NSObjectProtocol!
updateObserver = NotificationCenter.default.addObserver(forName: NSNotification.Name.NSFileHandleDataAvailable, object: outHandle, queue: nil, using: { notification in
let data = outHandle.availableData
if !data.isEmpty {
if let str = String(data: data, encoding: .utf8) {
print(str) // This is differently here.
}
outHandle.waitForDataInBackgroundAndNotify()
} else {
NotificationCenter.default.removeObserver(updateObserver!)
}
})
var errorObserver: NSObjectProtocol!
errorObserver = NotificationCenter.default.addObserver(forName: NSNotification.Name.NSFileHandleDataAvailable, object: errorHandle, queue: nil, using: { notification in
let data = errorHandle.availableData
if !data.isEmpty {
if let str = String(data: data, encoding: .utf8) {
print(str) // This is differently here.
}
errorHandle.waitForDataInBackgroundAndNotify()
} else {
NotificationCenter.default.removeObserver(errorObserver!)
}
})
var taskObserver : NSObjectProtocol!
taskObserver = NotificationCenter.default.addObserver(forName: Process.didTerminateNotification, object: task, queue: nil, using: { notification in
print("terminated")
NotificationCenter.default.removeObserver(taskObserver!)
})
task.launch()
Now this works for processes that print a new line with every change.
What does not work is to get outputs of processes that edit already printed lines (changin percentage or something like that).
In that case, the pipe is not pushing anything.
How would I handle that case. I thought about doing the output into a file, read that and at the end deleting it. Is that a possible solution?