【Logos】
Logos is a component of the Theos development suite that allows method hooking code to be written easily and clearly, using a set of special preprocessor directives.
Logos是Theos的三大组件之一，通过一系列的预处理命令，使得method hooking代码可以写得简单干净。
The syntax provided by Logos greatly simplifies the development of MobileSubstrate extensions ("tweaks") which can hook other methods throughout the OS. In this context, "method hooking" refers to a technique used to replace or modify methods of classes found in other applications on the phone.
Logos is distributed with Theos, and you can use Logos‘ syntax in any Theos-built project without any extra setup. For more information about Theos, visitits page.
1、You can use logify.pl to create a Logos source file from a header file that will log all of the functions of that header file. You can find logify.pl at $THEOS/bin/logify.pl and you would use it as so:
2、%init
用于初始化group，未提供group名时，使用‘_ungrouped‘。
3、%group
必须以%end结尾。一个%group可以包含多个%hook。必须用%init初始化的group才会生效。
4、%ctor
如果不显示指定，Theos会自动生成一个%ctor，并在里面调用%init(_ungrouped)。
5、%new
用于为一个现有classs添加新函数。
6、%c
等于于objc_getClass()。
参考：http://iphonedevwiki.net/index.php/Logos
原文：http://www.cnblogs.com/tekkaman/p/3721648.html