# undefined FileSystemManager.ftruncateSync(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
fd	string		yes	File descriptor. fd adopt FileSystemManager.open or FileSystemManager.openSync Interface acquisition
length	number		yes	Truncate position, default 0. if length Is less than the file length in bytes, only the first 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'）

# Return value

# undefined

# error

Error code	Error message	Introductions
	bad file descriptor	Invalid file descriptor
	fail permission denied	Specified fd No 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()
const fd = fs.openSync({
  filePath: `${wx.env.USER_DATA_PATH}/hello.txt`, 
  flag: 'a+'
})
fs.ftruncateSync({
  fd: fd,
  length: 10 // Truncate the file from the 10th byte
})