os_log into a App's local file

Question

AppDevVa OP

Created Jun ’18

Replies 6

Boosts 0

Views 4.5k

Participants 5

Hi Team,

I went through WWDC 2018 video on 405_measuring_performance_using_logging and would like to replace existing logging mechanism with os_log to gain its benifits with signposts to measure performance.

But there is main blocker as listed below:

1. Current logging mechanism provides easy way to share the App logs by click of button,without need of external systems like Mac/Windows/iTune and its specific to our app resulting in minimum file size in KBs.

How could we achieve this by migrating to os_log, as it logs into a common bulky sysdiagnose file?

1.Could we wrap os_log to log to a file in App's documents folder?

Simple sample code will be helpful, as I could not find more info on wrapping os_log.

2. Could I programatically access sysdiagnose with filters of "my catogery" and export into App's local folder to share as before?

Thanks a ton in Advance!

Answered by DTS Engineer in 315922022

1. Could we wrap os_log to log to a file in App's documents folder?

Wrapping

os_log

is not recommended. Specifically, it’s a bad idea to wrap

os_log

with a function because you undermine a lot of its smarts with regards efficiently storing constant strings. In C-based languages you can get around this by wrapping it with a macro, but that option is not available in Swift.

2. Could I programatically access sysdiagnose with filters of "my catogery" and export into App's local folder to share as before?

There’s no way to do this currently, but it would make a fine enhancement request.

FYI, and I only just learnt this myself, you don’t need to use iTunes to grab a sysdiagnose log. You can export it via Settings > Privacy > Analytics > Analytics Data. That doesn’t help with the file size, but it does smooth over one obstacle.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Boost

Answer 1

DTS Engineer OP

Apple

Jun ’18

Accepted Answer

1. Could we wrap os_log to log to a file in App's documents folder?

Wrapping

os_log

is not recommended. Specifically, it’s a bad idea to wrap

os_log

with a function because you undermine a lot of its smarts with regards efficiently storing constant strings. In C-based languages you can get around this by wrapping it with a macro, but that option is not available in Swift.

2. Could I programatically access sysdiagnose with filters of "my catogery" and export into App's local folder to share as before?

There’s no way to do this currently, but it would make a fine enhancement request.

FYI, and I only just learnt this myself, you don’t need to use iTunes to grab a sysdiagnose log. You can export it via Settings > Privacy > Analytics > Analytics Data. That doesn’t help with the file size, but it does smooth over one obstacle.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

0

Answer 2

AppDevVa OP

Jun ’18

Thank you Eskimo.

Could you please let me know more details on "In C-based languages you can get around this by wrapping it with a macro, but that option is not available in Swift."

Basic need is to use os_log to log to a local file instead of common file. Do we have macro that we could modify to direct it to log into local folder?

export it via Settings > Privacy > Analytics > Analytics Data solves the need to connect to iTunes but the file is so huge that it cannot be sent via mail and our customers are mobile only users with no access to Mac/Windows to download and send.

Thanks again!

0

Answer 3

DTS Engineer OP

Apple

Jun ’18

Swift does not support macros, so you can’t use that technique in Swift code. The alternatively is to write your own function that appends the data to a log file you control. There are serious negatives to do this, however. Specifically,

os_log

was designed to deal with a high volume of logging while minimising the impact of those writes on the flash storage.

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

0

Answer 4

bioche_ OP

Apr ’20

I was tempted to use os_log in future developments but it's still a pain to retrieve logs remotely. We actually have this framework on MacOS but it requires admin permission : https://docs.developer.st.apple.com/documentation/oslog

Fetching logs limited to our app process should be possible both on MacOS (without admin rights) and iOS. Is there any enhancement scheduled on the topic ? There's also https://github.com/apple/swift-log but it seems to be in its development phase and intended to provide a simple API facade.

Thanks in advance !

0

Answer 5

glaurent OP

Jul ’20

This is now possible in iOS 14 : https://developer.apple.com/documentation/oslog/oslogstore

0

Answer 6

kaunteya OP

3d

Swift does not support macros, so you can’t use that technique in Swift code.

Is it possible now since macro was introduced in Swift 5.9

0