1. Common NSFileManager file methods
-(NSData *)contentsAtPath:path //Read data from a file
-(BOOL)createFileAtPath: path contents:(NSData *)data attributes:attr //Write data to a file
-(BOOL)removeItemAtPath:path error:err //Remove a file
-(BOOL)moveItemAtPath: from toPath:to error:err //Rename or move a file (to cannot already exist)
-(BOOL)copyItemAtPath:from toPath:to error:err //Copy the file (to cannot already exist)
-(BOOL)contentsEqualAtPath:path andPath:path2 //Compare the contents of two files
-(BOOL)fileExistAtPath:path //Test whether the file exists
-(BOOL)isReadableFileAtPath:path //Test whether the file exists and whether the read operation can be performed
-(BOOL)isWriteableFileAtPath:path //Test whether the file exists and whether the write operation can be performed
-(NSDictionary *)attributesOfItemAtPath:path error:err //Get the attributes of the file
-(BOOL)setAttributesOfItemAtPath:attr error:err //Change the attributes of the file
2. Use a directory
-(NSString *)currentDirectoryPath //Get the current directory
-(BOOL)changeCurrentDirectoryPath:path //Change the current directory
-(BOOL)copyItemAtPath:from toPath:to error:err //Copy directory structure (to cannot already exist)
-(BOOL)createDirectoryAtPath:path withIntermediateDirectories:(BOOL)flag attribute:attr //Create a new directory
-(BOOL)fileExistAtPath:path isDirectory:(BOOL*)flag //Test whether the file is a directory (the result stored in the flag is YES/NO)
-(NSArray *)contentsOfDirectoryAtPath:path error:err //List directory contents
-(NSDirectoryEnumerator *)enumeratorAtPath:path //Enumerate the contents of the directory
-(BOOL)removeItemAtPath:path error:err //Remove empty directory
-(BOOL)moveItemAtPath:from toPath:to error:err //Rename or move a directory (to cannot already exist)
3. Common path tool method
+(NSString *)pathWithComponens:components //Construct a valid path based on the elements in components
-(NSArray *)pathComponents //Destruct the path and get the parts that make up this path
-(NSString *)lastPathComponent //Extract the last component of the path
-(NSString *)pathExtension //Extract its extension from the last component of the path
-(NSString *)stringByAppendingPathComponent:path //Add path to the end of existing path
-(NSString *)stringByAppendingPathExtension:ext //Add the specified extension to the last component of the path
-(NSString *)stringByDeletingLastPathComponent //Delete the last component of the path
-(NSString *)stringByDeletingPathExtension //从文件的最后一部分删除扩展名
-(NSString *)stringByExpandingTileInPath //将路径中代字符扩展成用户主目录（~）或指定用户的主目录（~user）
-(NSString *)stringByresolvingSymlinksInPath //尝试解析路径中的符号链接
-(NSString *)stringByStandardizingPath //通过尝试解析~、..（父目录符号）、.（当前目录符号）和符号链接来标准化路径
4、常用的路径工具函数
NSString* NSUserName(void) //返回当前用户的登录名
NSString* NSFullUserName(void) //返回当前用户的完整用户名
NSString* NSHomeDirectory(void) //返回当前用户主目录的路径
NSString* NSHomeDirectoryForUser(NSString* user) //返回用户user的主目录
NSString* NSTemporaryDirectory(void) //返回可用于创建临时文件的路径目录
5、常用的IOS目录
Documents（NSDocumentDirectory） //用于写入应用相关数据文件的目录，在ios中写入这里的文件能够与iTunes共享并访问，存储在这里的文件会自动备份到云端
Library/Caches（NSCachesDirectory） //用于写入应用支持文件的目录，保存应用程序再次启动需要的信息。iTunes不会对这个目录的内容进行备份
tmp（use NSTemporaryDirectory（）） //这个目录用于存放临时文件，只程序终止时需要移除这些文件，当应用程序不再需要这些临时文件时，应该将其从这个目录中删除
Library/Preferences //这个目录包含应用程序的偏好设置文件，使用 NSUserDefault类进行偏好设置文件的创建、读取和修改