fs.appendFile(path, data[, options], callback)

• path <string> | <Buffer> | <URL> | <number> 文件名或文件描述符
• data <string> | <Buffer>
• options <Object> | <string>
  • encoding <string> | <null> 默认值: 'utf8'
  • mode <integer> 默认值: 0o666
  • flag <string> 请参阅对文件系统 flags 的支持。 默认值: 'a'。
• callback <Function>
  • err <Error>

异步地将数据追加到文件，如果该文件尚不存在，则创建该文件。 data 可以是字符串或 Buffer。

fs.appendFile('message.txt', 'data to append', (err) => {
  if (err) throw err;
  console.log('The "data to append" was appended to file!');
});

如果 options 是字符串，则它指定编码：

fs.appendFile('message.txt', 'data to append', 'utf8', callback);

可以将 path 指定为已打开用于追加（使用 fs.open() 或 fs.openSync()）的数字文件描述符。 文件描述符不会自动关闭。

fs.open('message.txt', 'a', (err, fd) => {
  if (err) throw err;
  fs.appendFile(fd, 'data to append', 'utf8', (err) => {
    fs.close(fd, (err) => {
      if (err) throw err;
    });
    if (err) throw err;
  });
});

• path <string> | <Buffer> | <URL> | <number> filename or file descriptor
• data <string> | <Buffer>
• options <Object> | <string>
  • encoding <string> | <null> Default: 'utf8'
  • mode <integer> Default: 0o666
  • flag <string> See support of file system flags. Default: 'a'.
• callback <Function>
  • err <Error>

Asynchronously append data to a file, creating the file if it does not yet exist. data can be a string or a Buffer.

fs.appendFile('message.txt', 'data to append', (err) => {
  if (err) throw err;
  console.log('The "data to append" was appended to file!');
});

If options is a string, then it specifies the encoding:

fs.appendFile('message.txt', 'data to append', 'utf8', callback);

The path may be specified as a numeric file descriptor that has been opened for appending (using fs.open() or fs.openSync()). The file descriptor will not be closed automatically.

fs.open('message.txt', 'a', (err, fd) => {
  if (err) throw err;
  fs.appendFile(fd, 'data to append', 'utf8', (err) => {
    fs.close(fd, (err) => {
      if (err) throw err;
    });
    if (err) throw err;
  });
});