Compare If Two Arrays Are Equal

[kwalking]

Hello,

I am trying to create an if statement to compare if two arrays are exactly the same.
Why is my code not working?

char array_1 [4] = "AAAA";
char array_2 [4] = "AAAA";

void setup() {

Serial.begin(9600);
}

void loop() {

if (array_1 == array_2) {
Serial.println("Match");
}

else{
Serial.println("No Match");
}

delay(5000);

}

Thank you for any help.

[jfjlaros]

To compare two arrays, we need to check all the individual element, so in general, we need something like this.

for (size_t i = 0; i < 4; i++) {
  if (array_1[i] != array_2[i]) {
    // No match.
  }
}

In this particular case, you could also consider to use the strcmp function, you have to increase the array sizes by one though, to make room for the terminiation character.

[red_car]

if (strcmp(array_1, array_2) == 0))
  // they are equal.

[UKHeliBob]

As the arrays are C style strings you can use strcmp() to compare them

if (strcmp(array_1, array_2) == 0)
{
  Serial.println("Match");
}

[Danois90]

There is also memcmp which works on any data type and not "just" strings / char arrays..

[noiasca]

@kwalking
first,
please activate the compiler warnings in your IDE. Your sketch gives you two warnings:

C:\Daten\myrepository\Arduino\Forum no SVN\sketch_sep11a\sketch_sep11a.ino:1:20: warning: initializer-string for array of chars is too long [-fpermissive]
 char array_1 [4] = "AAAA";
                    ^~~~~~
C:\Daten\myrepository\Arduino\Forum no SVN\sketch_sep11a\sketch_sep11a.ino:2:20: warning: initializer-string for array of chars is too long [-fpermissive]
 char array_2 [4] = "AAAA";
                    ^~~~~~

"AAAA" will need 5 bytes, so it doesn't fit in your variable.

this should compile without warnings:

char array_1[4] {'A', 'A', 'A', 'A'};
char array_2[4] {'A', 'A', 'A', 'A'};

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

void loop() {
  if (!memcmp(array_1, array_2, 4))
  {
    Serial.println("Match");
  }
  else 
  {
    Serial.println("No Match");
  }
  delay(5000);
}