NSHomeDirectory();

NSString *path = NSHomeDirectory();
上面的代码得到的是应用程序目录的路径，在该目录下有三个文件夹：Documents、Library、temp以及一个.app包！
该目录下就是应用程序的沙盒，应用程序只能访问该目录下的文件夹！！！

请参考下面的例子：
1、
NSString *path1 = NSHomeDirectory();

NSLog(@"path1:%@", path1);
path1:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830
2、
NSString *path2 = [NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES) lastObject];

NSLog(@"path2:%@", path2);
path2:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830/Library/Caches
3、
NSString *path3 = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];

NSLog(@"path3:%@", path3);
path3:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830/Documents
4、
NSString *path4 = [NSHomeDirectory() stringByAppendingPathComponent:@"Documents"];

NSLog(@"path4:%@", path4);
path4:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830/Documents
5、
NSString *path5 = [NSHomeDirectory() stringByAppendingPathComponent:@"Library"];

NSLog(@"path5:%@", path5);
path5:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830/Library
6、
NSString *path6 = [NSHomeDirectory() stringByAppendingPathComponent:@"temp"];

NSLog(@"path6:%@", path6);
path6:/Users/yuanjun/Library/Application Support/iPhone Simulator/4.2/Applications/172DB70A-145B-4575-A31E-D501AC6EA830/temp