Serial.readStringUntil

Serial.readStringUntil() is a function in Arduino programming language that reads characters from the serial port and stores them in a string until a specified character is encountered. The function takes a single argument, which is the delimiter character that indicates the end of the string.

For example, the following code reads a string from the serial port until a newline character is encountered:

String inputString = "";

void setup() {
  Serial.begin(9600);
}

void loop() {
  if (Serial.available()) {
    char c = Serial.read();
    if (c == '\n') {
      Serial.print("Input string: ");
      Serial.println(inputString);
      inputString = "";
    } else {
      inputString += c;
    }
  }
}

This code declares a string variable called `inputString` and initializes it to an empty string. In the `loop()` function, the code checks if there are any characters available on the serial port using the `Serial.available()` function. If there are, it reads the character using the `Serial.read()` function and checks if it is a newline character (`\n`). If it is, it prints the input string to the serial monitor and resets the string to an empty value. If it is not a newline character, it appends the character to the `inputString` variable using the `+=` operator.