fs.read(fd, buffer, offset, length, position, callback)

fd 指定的文件中读取数据。

回调被赋予三个参数,(err, bytesRead, buffer)

如果此方法作为其 util.promisify() 版本被调用,则其将为具有 bytesReadbuffer 属性的 Object 返回 Promise

Read data from the file specified by fd.

buffer is the buffer that the data (read from the fd) will be written to.

offset is the offset in the buffer to start writing at.

length is an integer specifying the number of bytes to read.

position is an argument specifying where to begin reading from in the file. If position is null, data will be read from the current file position, and the file position will be updated. If position is an integer, the file position will remain unchanged.

The callback is given the three arguments, (err, bytesRead, buffer).

If this method is invoked as its util.promisify()ed version, it returns a Promise for an Object with bytesRead and buffer properties.