fs.writev(fd, buffers[, position], callback)

    使用 writev()ArrayBufferView 数组写入 fd 指定的文件。

    Write an array of ArrayBufferViews to the file specified by fd using writev().

    position is 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.

    The callback will be given three arguments: err, bytesWritten, and buffers. bytesWritten is how many bytes were written from buffers.

    If this method is util.promisify()ed, it returns a promise for an Object with bytesWritten and buffers properties.

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

    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.