# FileSystemManager.truncate(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

Truncate file contents

# parameter

# Object object

attribute	type	Default values	Required	Introductions
filePath	string		yes	File path to truncate (Local path)
length	number	0	no	Truncate position, default 0. if length Less than the length of the file (bytes), only the front length Four bytes will remain in the file and the rest will be deletedif length Is greater than the file length, it will be expanded, and the extension will be filled with empty bytes0'）
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.fail callback

# parameter

# Object res

attribute	type	Introductions
errMsg	string	Error message

res.errMsg Legal value

value	Introductions	Minimum version
fail No such file or directory, open ${filePath}	Specified filePath Directory does not exist
fail illegal operation on a directory, open "${filePath}"	Specified filePath It's an existing directory.
fail permission denied, open ${dirPath}	Specified filePath Path does not have write permissions
fail the maximum size of the file storage limit is exceeded	Insufficient storage space
fail sdcard not mounted	android sdcard Mount failure

# sample code

const fs = wx.getFileSystemManager()
fs.truncate({
  filePath: `${wx.env.USER_DATA_PATH}/hello.txt`, 
  length: 10, // Truncating from the 10th byte
  success(res) {
    console.log(res)
  }
})