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

string 写入 fd 指定的文件。

position 指从文件开头数据应被写入的偏移量。 如果 typeof position !== 'number',则数据将写入当前位置。 参见 pwrite(2)

encoding 是预期的字符串编码。

回调将接收参数 (err, written, string),其中 written 指定传入的字符串需要被写入的字节数。 写入的字节数不一定与写入的字符串字符数相同。 参见 Buffer.byteLength

在同一个文件上多次使用 fs.write() 而不等待回调是不安全的。 对于这种情况,建议使用 fs.createWriteStream()

在 Linux 上,以追加模式打开文件时,位置写入不起作用。 内核会忽略位置参数,并始终将数据追加到文件末尾。

在 Windows 上,如果文件描述符连接到控制台(例如 fd == 1stdout),则默认情况下无论使用何种编码,都无法正确呈现包含非 ASCII 字符的字符串。 通过使用 chcp 65001 命令更改激活的代码页,可以将控制台配置为可正确呈现 UTF-8。 有关更多详细信息,请参阅 chcp 文档。

Write string to the file specified by fd. If string is not a string, then the value will be coerced to one.

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.