Export OSLog To File

LogReportCreator.swift

import Foundation
import OSLog

@available(iOS 15.0, *)
final class LogReportCreator {
    
    enum LogReportCreatorError: Error {
        case noEntries
        case unableToFindCachesDirectory
        case unknownError(error: Error)
    }
    
    func generateLogFile(completion: @escaping ((Result<URL, LogReportCreatorError>) -> Void)) {
        DispatchQueue.global(qos: .userInitiated).async {
            do {
                let store = try OSLogStore(scope: .currentProcessIdentifier)
                let position = store.position(timeIntervalSinceEnd: -60.0*60.0*24)
                let entries = try store.getEntries(with: [], at: position, matching: nil)
                var logString = String()
                for e in entries {
                    logString.append(contentsOf: e.date.ISO8601Format())
                    logString.append(contentsOf: ": ")
                    logString.append(contentsOf: e.composedMessage)
                    logString.append(contentsOf: "\n")
                }
                
                guard logString.isEmpty == false else {
                    completion(.failure(.noEntries))
                    return
                }
                
                guard let path = FileManager.default.urls(for: .cachesDirectory, in: .userDomainMask).first else {
                    completion(.failure(.unableToFindCachesDirectory))
                    return
                }
                
                let filename = path.appendingPathComponent("\(Date().ISO8601Format()).log")

                try logString.write(to: filename, atomically: true, encoding: String.Encoding.utf8)
                
                completion(.success(filename))
            }
            catch {
                completion(.failure(.unknownError(error: error)))
            }
        }
    }
    
}