/* Comparing Strings Examples of how to compare strings using the comparison operators created 27 July 2010 modified 2 Apr 2012 by Tom Igoe http://arduino.cc/en/Tutorial/StringComparisonOperators This example code is in the public domain. */ String stringOne, stringTwo; void setup() { // Open serial communications and wait for port to open: Serial.begin(9600); while (!Serial) { ; // wait for serial port to connect. Needed for Leonardo only } stringOne = String("this"); stringTwo = String("that"); // send an intro: Serial.println("\n\nComparing Strings:"); Serial.println(); } void loop() { // two strings equal: if (stringOne == "this") { Serial.println("StringOne == \"this\""); } // two strings not equal: if (stringOne != stringTwo) { Serial.println(stringOne + " =! " + stringTwo); } // two strings not equal (case sensitivity matters): stringOne = "This"; stringTwo = "this"; if (stringOne != stringTwo) { Serial.println(stringOne + " =! " + stringTwo); } // you can also use equals() to see if two strings are the same: if (stringOne.equals(stringTwo)) { Serial.println(stringOne + " equals " + stringTwo); } else { Serial.println(stringOne + " does not equal " + stringTwo); } // or perhaps you want to ignore case: if (stringOne.equalsIgnoreCase(stringTwo)) { Serial.println(stringOne + " equals (ignoring case) " + stringTwo); } else { Serial.println(stringOne + " does not equal (ignoring case) " + stringTwo); } // a numeric string compared to the number it represents: stringOne = "1"; int numberOne = 1; if (stringOne.toInt() == numberOne) { Serial.println(stringOne + " = " + numberOne); } // two numeric strings compared: stringOne = "2"; stringTwo = "1"; if (stringOne >= stringTwo) { Serial.println(stringOne + " >= " + stringTwo); } // comparison operators can be used to compare strings for alphabetic sorting too: stringOne = String("Brown"); if (stringOne < "Charles") { Serial.println(stringOne + " < Charles"); } if (stringOne > "Adams") { Serial.println(stringOne + " > Adams"); } if (stringOne <= "Browne") { Serial.println(stringOne + " <= Browne"); } if (stringOne >= "Brow") { Serial.println(stringOne + " >= Brow"); } // the compareTo() operator also allows you to compare strings // it evaluates on the first character that's different. // if the first character of the string you're comparing to // comes first in alphanumeric order, then compareTo() is greater than 0: stringOne = "Cucumber"; stringTwo = "Cucuracha"; if (stringOne.compareTo(stringTwo) < 0 ) { Serial.println(stringOne + " comes before " + stringTwo); } else { Serial.println(stringOne + " comes after " + stringTwo); } delay(10000); // because the next part is a loop: // compareTo() is handy when you've got strings with numbers in them too: while (true) { stringOne = "Sensor: "; stringTwo = "Sensor: "; stringOne += analogRead(A0); stringTwo += analogRead(A5); if (stringOne.compareTo(stringTwo) < 0 ) { Serial.println(stringOne + " comes before " + stringTwo); } else { Serial.println(stringOne + " comes after " + stringTwo); } } }