NSFileHandle类主要对文件内容进行读取和写入操作
NSFileManager类主要对文件的操作（删除、修改、移动、复制等等）
常用处理方法
+ (id)fileHandleForReadingAtPath:(NSString *)path 打开一个文件准备读取
+ (id)fileHandleForWritingAtPath:(NSString *)path 打开一个文件准备写入
+ (id)fileHandleForUpdatingAtPath:(NSString *)path 打开一个文件准备更新
- (NSData *)availableData; 从设备或通道返回可用的数据
- (NSData *)readDataToEndOfFile; 从当前的节点读取到文件的末尾
- (NSData *)readDataOfLength:(NSUInteger)length; 从当前节点开始读取指定的长度数据
- (void)writeData:(NSData *)data; 写入数据
- (unsigned long long)offsetInFile; 获取当前文件的偏移量
- (void)seekToFileOffset:(unsigned long long)offset; 跳到指定文件的偏移量
- (unsigned long long)seekToEndOfFile; 跳到文件末尾
- (void)truncateFileAtOffset:(unsigned long long)offset; 将文件的长度设为offset字节
- (void)closeFile; 关闭文件
/* 向文件添加数据*/
向文件追加数据
//获取沙盒Documents路径
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDictionary = [paths objectAtIndex:0];
//创建文件
NSFileManager *fileManager = [NSFileManager defaultManager];
NSString *testDictionary = [documentDictionary stringByAppendingPathComponent:@"test"];
[fileManager createDirectoryAtPath:testDictionary withIntermediateDirectories:YES attributes:nil error:nil];
NSString *sourcePath = [testDictionary stringByAppendingPathComponent:@"testfile.text"];
//先写一个空字符进去
NSString *tempStr = @“”;
[tempStr writeToFile:sourcePath atomically:YES encoding:NSUTF8StringEncoding error:nil];
//打开这个testfile文件准备更新
NSFileHandle *fielHandle = [NSFileHandle fileHandleForUpdatingAtPath:sourcePath];
[fileHandle seekToEndOfFile]; //将节点跳到文件的末尾
NSString *str = @"追加的数据" ;
NSData* stringData = [str dataUsingEncoding:NSUTF8StringEncoding];
[fileHandle writeData:stringData]; 追加写入数据
//读取数据
NSData *reader = [NSData dataWithContentsOfFile:_testHeartFilePath];
NSString *tempStr = [[NSString alloc] initWithData:reader2 encoding:NSUTF8StringEncoding];
[fileHandle closeFile];