FileSystemManager.write

Introduction

Writes to a file.

Usage Restrictions

Supported in basic library version 3.0.0 or higher.

Parameters

Object object

Attribute	Type	Default	Required	Description
fd	string		Yes	File descriptor obtained through the FileSystemManager.open interface.
data	string		Yes	Content to be written, with a type of String (ArrayBuffer is not supported at the moment).
encoding	string	utf8	No	Only effective when the data type is String, specifies the character encoding of the file to be written, defaulting to utf8. Valid values: 1. ascii 2. base64 3. binary 4. hex 5. ucs2 (read in little endian) 6. ucs-2 (read in little endian) 7. utf16le (read in little endian) 8. utf-16le (read in little endian) 9. utf-8 10. utf8 11. latin1
position	number	0	No	Specifies the offset from the beginning of the file where the data is to be written. When position is not passed or a non-Number value is passed, the data will be written at the current pointer position.
success	function		No	Callback function called when the interface is successfully called.
fail	function		No	Callback function called when the interface call fails.
complete	function		No	Callback function called when the interface call ends (executed regardless of success or failure).

object.success

Callback Function

Parameters

Object res

Attribute	Type	Description
bytesWritten	number	Number of bytes actually written to the file (note that the number of bytes written may not be the same as the number of characters in the written string).
success	string	true - set successfully

object.fail

Callback Function

Parameters

Object res

Attribute	Type	Description
errMsg	string	Error message
success	string	false - failed to set

errMsg Explanation

Error Message	Description
parameter error: F10001	Invalid parameter
bad file descriptor: F10003	Invalid file descriptor
fail permission denied: F10005	The specified fd path does not have read permission
the named is ${encoding} charset is not supported!	The current character encoding is not supported

Sample Code

// pages/index/index.js
Page({
  write() {
    const fs = dlt.getFileSystemManager();
    // Open the file
    fs.open({
      filePath: `${dlt.env.USER_DATA_PATH}/hello.txt`,
      flag: 'a+',
      success(res) {
        // Write to the file
        fs.write({
          fd: res.fd,
          data: 'some text',
          success(res) {
            console.log(res.bytesWritten);
          },
        });
      },
    });
  },
});