fs.write(fd, string[, position[, encoding]], callback)

将 string 写入 fd 指定的文件。 如果 string 不是字符串，或者不是具有自有的 toString 函数属性的对象，则会抛出异常。

• fd <integer>
• string <string> | <Object>
• position <integer> | <null> Default: null
• encoding <string> Default: 'utf8'
• callback <Function>
  • err <Error>
  • written <integer>
  • string <string>

Write string to the file specified by fd. If string is not a string, or an object with an own toString function property, then an exception is thrown.

position refers to the offset from the beginning of the file where this data should be written. If typeof position !== 'number' the data will be written at the current position. See pwrite(2).

encoding is the expected string encoding.

The callback will receive the arguments (err, written, string) where written specifies how many bytes the passed string required to be written. Bytes written is not necessarily the same as string characters written. See Buffer.byteLength.

It is unsafe to use fs.write() multiple times on the same file without waiting for the callback. For this scenario, fs.createWriteStream() is recommended.

On Linux, positional writes don't work when the file is opened in append mode. The kernel ignores the position argument and always appends the data to the end of the file.

On Windows, if the file descriptor is connected to the console (e.g. fd == 1 or stdout) a string containing non-ASCII characters will not be rendered properly by default, regardless of the encoding used. It is possible to configure the console to render UTF-8 properly by changing the active codepage with the chcp 65001 command. See the chcp docs for more details.