# FileSystemManager.read(Object object)

Start from base library version 2.16.1. Please remaining backward compatible.

with Promise style call: Not supported

Mini Program plugin: Support, need to Mini Program base library version no less than 2.19.2

Read Files

# parameter

# Object object

attribute	type	Default values	Required	Introductions
fd	string		yes	File descriptor. fd adopt FileSystemManager.open or FileSystemManager.openSync Interface acquisition
arrayBuffer	ArrayBuffer		yes	The buffer to which the data is written must be ArrayBuffer Example
offset	number	0	no	Write offset in buffer, default 0
length	number	0	no	Number of bytes to read from the file, default 0
position	number		no	The starting position of a file read, such as no upload or upload Null, it is read from the position of the current file pointer. if position Is a positive integer, the file pointer position remains the same and is converted from the position Read the file.
success	function		no	Interface calls the successful callback function
fail	function		no	Interface calls failed callback functions
complete	function		no	Callback function at the end of an interface call (both successful and unsuccessful calls are executed)

# object.success callback

# parameter

# Object res

attribute	type	Introductions
bytesRead	number	Number of bytes actually read
arrayBuffer	ArrayBuffer	Object that is written to the buffer, that is, the arrayBuffer

# object.fail callback

# parameter

# Object res

attribute	type	Introductions
errMsg	string	Error message

res.errMsg Legal value

value	Introductions	Minimum version
bad file descriptor	Invalid file descriptor
fail permission denied	Specified fd Path not read
fail the value of "offset" is out of range	Incoming offset illegal
fail the value of "length" is out of range	Incoming length illegal
fail sdcard not mounted	android sdcard Mount failure
bad file descriptor	Invalid file descriptor

# sample code

const fs = wx.getFileSystemManager()
const ab = new ArrayBuffer(1024)
// Open the file
fs.open({
  filePath: `${wx.env.USER_DATA_PATH}/hello.txt`, 
  flag: 'a+',
  success(res) {
    // Read file to ArrayBuffer in
    fs.read({
      fd: res.fd,
      arrayBuffer: AB,
      length: 10,
      success(res) {
        console.log(res)
      }
    })
  }
})