I’m using an ESP32 and the File System LittleFS to make a file. Sometimes, like in the title, I need to replace a single line in the file but i don’t want to copy the entire file. Is it possible? How can I do it?
To make problem easier, all lines can be of the same length. Also the new line.

I have tried with this code:

#include<LittleFS.h>

String stringToSearchInLine="Line 2";
String newSubString="123";


void replacePDU(const String &searchString, const String &PDU_Name) {
  File file = LittleFS.open("/ReplaceLineTest.txt", FILE_WRITE);
  if (!file) {
    Serial.println("File open error!!");
    return;
  }
  
  while (file.available()) {
    // Read current position
    int position = file.position();
    
    // read a line
    String line = file.readStringUntil('n');
    
    // search something in the lines to select the one to replace
    if (line.indexOf(searchString) != -1) {     
  
      int pduIndex = line.indexOf("---");
      if (pduIndex != -1) {
        
        line.replace("---", PDU_Name); //new_Name has length = 3;
        
        // return to the position of the line to be replaced
        file.seek(position);
        file.print(line);
        file.print("n");
        break;
      }else{
        Serial.println("PDU Name is already assigned");
      }
    }
  }
}


void setup(){
  Serial.begin(115200);

  if (!LittleFS.begin()) {
    Serial.println("Error Initializing the file system");
  }else{
    Serial.println("File System ready");
  }

  File file = LittleFS.open("/ReplaceLineTest.txt", FILE_WRITE);

  if (!file) {
    Serial.println("Open File to write error.");
    return;
  }else{
    file.println("Line 1 ---");
    file.println("Line 2 ---");
    file.println("Line 3 ---");
    file.println("Line 4 ---");
  
    file.close();
  }

  //Read and Stamp original file
  file = LittleFS.open("/ReplaceLineTest.txt");
  Serial.println("  Read from file:");
  while(file.available()){
    Serial.write(file.read());
  }
  file.close();


  replacePDU(stringToSearchInLine, newSubString);


  //Read and Stamp modified file
  file = LittleFS.open("/ReplaceLineTest.txt");
  if(!file){
    Serial.println("Problem occurred during opening file");
  }else{
    Serial.println("  Read from file:");
    while(file.available()){
      Serial.write(file.read());
    }
    file.close();
  }
}


void loop(){
  
}

The result was always a blank file.