Improved Logging

Pelaez — Sun, 25 Oct 2009 05:58:08 +0000

This is an improved logging technique I developed in the last couple of days. It’s not to debug an specific problem, but to get a general idea of where your bug is, and if there are no bugs, to know the stack of methods called.

It’s quite simple, but it does require some work to implement. If you have a big project, it could take some time to implement.

Instructions:

First, get this class, and add it to your project.

Then, in your prefix file, add the following lines:

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#import "KPLogHelper.h"
#define LOG_IN NSLog(@"XX:%@ %s",[KPLogHelper indent:1], __PRETTY_FUNCTION__);
#define LOG_OUT NSLog(@"XX:%@ %s",[KPLogHelper indent:-1], __PRETTY_FUNCTION__);
#define LOG_NO NSLog(@"XX:%@ %s",[KPLogHelper indent:0], __PRETTY_FUNCTION__);
#define LOG(x) NSLog(@"iPC:%@ %@", [KPLogHelper indent:0], x);

The XX should be two characters to filter your logs, it’s not necesary, but it’s useful. You can find more about that here.

And finally, at the beginning of every method you want to log, add LOG_IN, at the end of the method, and before any returns, add LOG_OUT.

If it’s a really small method and you don’t want to know where it starts and when it ends, but only when it happened, just add LOG_NO.

If you want to log with a custom string while respecting the indent level LOG(NSString *here).

The result in the log will be a message when the method is called with an indent level, and the methods that are called before it ends will have an indentation level greater by one, then the indentation level will be reduced by one when the method ends.

It will look something like:

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>>> Method 1 signature //When the first method begins: LOG_IN
>>>>>> Method 2 signature //When the second method is called by the 1st: LOG_ING
====== Method 3 signature //When the 3rd method is called by 2nd: LOG_NO
<<<<<< Method 2 Signature //When the second method returns: LOG_OUT
<<< Method 2 signature //When the first method returns: LOG_OUT

To stop showing the log, just comment the methods so it looks like this:

1	#define LOG_IN //NSLog(@"XX:%@ %s",[KPLogHelper indent:1], __PRETTY_FUNCTION__);

NOTE: Make sure you disable this logging before releasing you app, as it’s a little heavier than the standard logging (due to the calculations to make the indent) and will slow down your app.

NSLog and Syslog

Pelaez — Sun, 23 Aug 2009 23:50:25 +0000

To help you debugging, there’s the NSLog method, and Syslog, on Cydia, by saurik, enables logging in the iDevice.

To use it, simply put:

NSLog(@"A string here");

Then, when executed, it will write that to a file on the iDevice, on /var/log/syslog.

To see the log, you can open the file on a text editor, or simply use:

$ cat /var/log/syslog

To make it easier to find the logs that matter to you (because keep in mind that it will log whatever the Springboard and other apps want to log), what I do is to add some letters at the beginning of the string.
Imagine we are making an app called “Kernel Panic App”, so when you log something, you would do it like this:

NSLog(@"KPA: Successfully saved the file");

Then, to see only tags by that app, we would do this on the terminal:

$ cat /var/log/syslog | grep KPA

That will output only the lines that have our tag on it. A couple of lines that don’t matter to us (depending on what tag we are using) might slip, but certainly, they will be a lot less.

If you want to save that output into a file, you can do this on the terminal:

$ cat /var/log/syslog | grep KPA >> MyLog1

Also, for a better log, you can put variables in the string. It’s a string format, so it accepts things like:

NSLog(@"Objects: %i, User: %@", anInt, anNSString)

That way, you can produce a better log, by outputting numbers and strings that might be useful to know what is your app doing.

Hope you can find a good use for this!

Please send me an e-mail if I got anything wrong, so I can fix it.

Kernel Panic » syslog

Improved Logging

Instructions:

NSLog and Syslog