在iOS开发中，通常我们Xcode工程的一个最终的Product是app格式，而如果你在Finder中点击“显示包内容”看看app里都有什 么，你会看到里面的好多东西，有nib、plist、mobileprovision和各种图片资源等，而其中最重要的一个文件就是被标为“Unix可执 行文件”(用file查看是Mach-O executable arm)类型的文件。我们的代码逻辑都在这里面。

比如这个可执行文件名为ex，我们通过使用:

otool -L ex

就能看到这个应用运行所需要的系统库，显示结果的格式通常如下：

/usr/lib/libicucore.A.dylib (compatibility version 1.0.0, current version 51.1.0) /usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current version 100.0.0) /usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 221.0.0) /System/Library/Frameworks/AdSupport.framework/AdSupport (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/Accelerate.framework/Accelerate (compatibility version 1.0.0, current version 4.0.0) /System/Library/Frameworks/OpenGLES.framework/OpenGLES (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/Accounts.framework/Accounts (compatibility version 1.0.0, current version 113.0.0) /System/Library/Frameworks/Social.framework/Social (compatibility version 1.0.0, current version 87.0.0) /System/Library/Frameworks/MapKit.framework/MapKit (compatibility version 1.0.0, current version 14.0.0) /System/Library/Frameworks/ImageIO.framework/ImageIO (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/AssetsLibrary.framework/AssetsLibrary (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/Security.framework/Security (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/MobileCoreServices.framework/MobileCoreServices (compatibility version 1.0.0, current version 51.0.0) /System/Library/Frameworks/CoreVideo.framework/CoreVideo (compatibility version 1.2.0, current version 1.8.0) /System/Library/Frameworks/MessageUI.framework/MessageUI (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/CoreLocation.framework/CoreLocation (compatibility version 1.0.0, current version 1613.5.2) /System/Library/Frameworks/SystemConfiguration.framework/SystemConfiguration (compatibility version 1.0.0, current version 615.0.0) /System/Library/Frameworks/CoreData.framework/CoreData (compatibility version 1.0.0, current version 479.2.0) /System/Library/Frameworks/CoreTelephony.framework/CoreTelephony (compatibility version 1.0.0, current version 1645.0.0) /System/Library/Frameworks/CoreText.framework/CoreText (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/MediaPlayer.framework/MediaPlayer (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/CoreMedia.framework/CoreMedia (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/AudioToolbox.framework/AudioToolbox (compatibility version 1.0.0, current version 492.0.0) /System/Library/Frameworks/CFNetwork.framework/CFNetwork (compatibility version 1.0.0, current version 672.0.8) /System/Library/Frameworks/QuartzCore.framework/QuartzCore (compatibility version 1.2.0, current version 1.8.0) /System/Library/Frameworks/AddressBookUI.framework/AddressBookUI (compatibility version 1.0.0, current version 33.0.0) /System/Library/Frameworks/AddressBook.framework/AddressBook (compatibility version 1.0.0, current version 30.0.0) /System/Library/Frameworks/AVFoundation.framework/AVFoundation (compatibility version 1.0.0, current version 2.0.0) /System/Library/Frameworks/UIKit.framework/UIKit (compatibility version 1.0.0, current version 2903.23.0) /System/Library/Frameworks/Foundation.framework/Foundation (compatibility version 300.0.0, current version 1047.22.0) /System/Library/Frameworks/CoreGraphics.framework/CoreGraphics (compatibility version 64.0.0, current version 600.0.0) /usr/lib/libsqlite3.dylib (compatibility version 9.0.0, current version 158.0.0) /usr/lib/libz.1.dylib (compatibility version 1.0.0, current version 1.2.5) /usr/lib/libobjc.A.dylib (compatibility version 1.0.0, current version 228.0.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1198.0.0) /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation (compatibility version 150.0.0, current version 847.21.0)