怎么判断ios 版本

获取进程信息和设备信息（包括设备类型，序列号，ios版本等）
[[nsprocessInfo processInfo] globallyUniqueString],
[[nsprocessInfo processInfo] hostname],
[[nsprocessInfo processInfo] operatingSystemname],
[[nsprocessInfo processInfo] operatingSystemVersionString],
[[nsprocessInfo processInfo] physicalMemory],
[[nsprocessInfo processInfo] processname]);
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[UIDevice currentDevice].uniqueIDentifIEr,
[UIDevice currentDevice].name,
[UIDevice currentDevice].systemname,
[UIDevice currentDevice].systemVersion,
[UIDevice currentDevice].model,
[UIDevice currentDevice].localizedModel,
[UIDevice currentDevice].batterylevel
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NSLog([[UIDevice currentDevice] name]); // name of the phone as named by user
NSLog([[UIDevice currentDevice] uniqueIDentifIEr]); // A GUID like string
NSLog([[UIDevice currentDevice] systemname]); // "iPhone OS"
NSLog([[UIDevice currentDevice] systemVersion]); // "2.2.1"
NSLog([[UIDevice currentDevice] model]); // "iPhone" on both devices
NSLog([[UIDevice currentDevice] localizedModel]); // "iPhone" on both devices

转自：http://blog.csdn.net/jinglijun/article/details/7292674