在iOS/os 系统中程序编译以后我们都可以找到对应路径下的可执行（executable）文件，然而我们在查找系统动态类似于 UIKit MapKit AVKit CFNetwork 等一些系统库的可执行文件时候到其默认输出路径/System/Library/Frameworks/UIKit.framework中无法找到对应的executable文件，这是由于苹果官方为了提高性能，不再将动态库单独存放，而是将绝大多数系统动态库都打包存放在一个缓存文件中(dyld shared cache)，默认缓存路径为/System/Library/Cache/com.app.dyld,在这个文件夹下，我们可以在下图看到两种架构的动态库缓存文件
这个动态共享库中就包含着我们常用的调用系统库，类似UIKit等常用系统库，我们需要做的就是将这个库中的动态库一个个抽取出来，抽取后，我们会得到以下系统库文件
这样我们就可以单独拿到一个系统动态 (dynamically linked shared library)库的,这样我们就可以去分析单一的库了。
cd dsc_extractor // cd到dsc_extractor文件夹下
./dsc_extractor xx oo // xx 是指待抽取的共享缓存库文件名 oo 是指待输出的文件夹
或者你输入 ./dsc_extractor 会打印出你需要拼接的参数
usage: dsc_extractor <path-to-cache-file> <path-to-device-dir>
上述文件如果需要在不指定路径下执行，可以 cp dsc_extractor /usr/bin or /usr/local/bin
如果上述方法不好使，可以编辑 .bash_profile 指定路径export $PATH。
git clone https://github.com/markdashi/dsc_extractor.git
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