os_log configuration iOS

I found an older post that got no reply:

https://forums.developer.apple.com/message/178405#178405

It's interesting that Apple has profiles for controlloing the log levels. These are used to turn up logging for programs like messages to revel more info for use in radars:

https://developer.apple.com/bug-reporting/profiles-and-logs/

Any chance I can get word if this is offically supported for 3rd parties? I suppose I'll file a coulpe of feature request radars. 🙂

You can configure os_log with different log levels like:

os_log("%{public}@", log: OSLog(subsystem: "com.example", category: "app"), type: .default, "default log level")
os_log("%{public}@", log: OSLog(subsystem: "com.example", category: "app"), type: .debug, "debug log level")

I have written a logging library JSLogger to simplify the logging using

os_log

Thanks for the response Kadaj,

But I'm looking for an answer about how to configure the behavior of the logs vs the actual labeling of the logs.

For example, I would be nice to be able to disable debugging for specific categories.

Here's the real answer:

You need to use add an OSLogPreferences dictionary to your app's "Info.plist" file.

For details, open Terminal and type man 5 os_log. The general structure will be something like this:

    <key>OSLogPreferences</key>
    <dict>
        <key>put.your.subsystem.name.here</key>
        <dict>
            <key>put.your.category.name.here</key>
            <dict>
                <key>Level</key>
                <dict>
                    <key>Enable</key>
                    <string>Debug</string>
                    <key>Persist</key>
                    <string>Debug</string>
                </dict>
                <key>Enable-Private-Data</key>
                <true/>
            </dict>
        </dict>
    </dict>

In Xcode, this looks like this:

You enter a subsystem and category when you instantiate your Logger in Swift, something like this:

import OSLog

let myLogger = Logger(subsystem: "com.example.mycompany.mysubsystem", category: "kittens")
logger.log("Hello there!")

The dictionary under OSLogPreferences can have multiple subsystems, and each subsystem can list one or more categories. You can also use the special category key, DEFAULT-OPTIONS, to define common settings for all categories in a subsystem. So, if you used the single subsystem, com.example.mycompany.mysubsystem, you could do something like this:

    <key>OSLogPreferences</key>
    <dict>
        <key>com.example.mycompany.mysubsystem</key>
        <dict>
            <key>DEFAULT-OPTIONS</key>
            <dict>
                <key>Level</key>
                <dict>
                    <key>Enable</key>
                    <string>Debug</string>
                    <key>Persist</key>
                    <string>Debug</string>
                </dict>
                <key>Enable-Private-Data</key>
                <true/>
            </dict>
        </dict>
    </dict>

In both of my examples, the Enable-Private-Data key isn't required, but I include it so that everything doesn't say when you try to look at your logs. Thanks to @eskimo for pointing me to this man page.

Here's the real answer

Indeed. And for more system log hints and tips, see Your Friend the System Log.

Share and Enjoy
—
Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"