Unified logging is a critical aspect of modern software development and system administration, providing a centralized way to collect, store, and analyze log data. In the Apple ecosystem, Unified Logging is a powerful framework that allows developers and system administrators to capture detailed logs from macOS and iOS devices. This system is essential for debugging, performance monitoring, and security auditing. This article will introduce you to Apple's Unified Logging System, its importance, and how to effectively use it in your development and administrative tasks.

Examples:

Example 1: Basic Logging in Swift

To get started with Unified Logging in a macOS or iOS application, you can use the os framework in Swift. Here’s a simple example of how to log messages:

import os.log



let logger = OSLog(subsystem: "com.example.myapp", category: "networking")



os_log("Network request started", log: logger, type: .info)

os_log("Network request failed with error: %@", log: logger, type: .error, "Timeout")

This code snippet demonstrates how to create a logger with a specific subsystem and category, and how to log informational and error messages.

Example 2: Viewing Logs via Terminal

You can view logs generated by the Unified Logging System using the log command in the Terminal. Here’s how to retrieve logs for a specific subsystem:

log show --predicate 'subsystem == "com.example.myapp"' --info

This command filters logs to show only those related to the specified subsystem and includes informational messages.

Example 3: Real-Time Log Streaming

For real-time log monitoring, you can use the log stream command. This is useful for live debugging sessions:

log stream --predicate 'subsystem == "com.example.myapp"'

This command streams logs in real-time for the specified subsystem.

Example 4: Custom Log Levels

You can define custom log levels to better organize your log messages. Here’s how to set up custom log levels in Swift:

import os.log



extension OSLogType {

    static let debug = OSLogType(rawValue: OSLogType.debug.rawValue)

    static let fault = OSLogType(rawValue: OSLogType.fault.rawValue)

}



let logger = OSLog(subsystem: "com.example.myapp", category: "custom")



os_log("Debugging message", log: logger, type: .debug)

os_log("Fault occurred", log: logger, type: .fault)

This example shows how to extend OSLogType to include custom log levels and how to use them in your logging.