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In this tutorial, we will discuss strcmp()comparing two strings using the compare function in Arduino.

Arduino strcmp()Functions

strcmp()Function compares two strings in Arduino. strcmp()The function compares the ASCII values ​​of the characters present in two strings and then returns three types of output values ​​based on the ASCII values ​​of the characters.

The characters on the keyboard have unique ASCII values, for example athe ASCII value of the character is 65. Following is strcmp()the basic syntax of the function.

output = strcmp(string1, string2);

The above syntax will return a negative number if all the characters present in both the strings are identical, 0if the characters in the first string that do not match the characters of the second string have lower ASCII values ​​than the characters in the second string, it will return a positive number if the ASCII values ​​of the non-matching characters of the first string are greater than the characters of the second string.

If the difference between the ASCII values ​​of the first two characters is zero, strcmp()the function will move on to the next character, and so on, and when all characters have been compared, it will also return 0, which will indicate that the two strings are equal.

If the ASCII values ​​of the two characters are not equal to 0, the function will stop and return the difference between the ASCII values ​​of the current unmatched characters.

For example, let's define two identical strings and strcmp()compare them using the function in Arduino.

See the code below.

int output;
void setup() {
  char* string1 = "hello";
  char* string2 = "hello";
  output = strcmp(string1, string2);
  Serial.begin(9600);
  Serial.println(output);
}
void loop() {}

Output:

0

strcmp()The input to the function should be a constant string. In the above code, we use the Arduino serial monitor to display strcmp()the output of the function.

Serial.begin()The function is used to initialize the serial monitor and Serial.println()the function prints the given value on the serial monitor window.

We can also use the output of a function in conditional statements strcmp(), such as ifthe if statement to perform specific tasks, such as if the output is equal to 0, we can print on the serial monitor that two strings are equal.

We can also use other functions of Arduino to compare two strings such as compareTo()and equals()functions. Check out this link for more details on string comparison in Arduino.