How do i compare a string if it has been entered two time using serial.read input?

[emanuelnegese]

If the same string is read by serial.read then display that it has been already entered.

[UKHeliBob]

Please post a complete sketch showing what you are trying to do

Do yo, for instance, need to compare 2 Strings (capital S) or 2 strings (lowercase s) ?

[LarryD]

See:

strcmp

[groundFungus]

Read the forum guidelines to see how to properly post code.

Use the IDE autoformat tool (ctrl-t or Tools, Auto format) before posting code in code tags.

[emanuelnegese]

int count = 0;
char c;
String id;

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

void loop() {
while (Serial.available() > 0)
{
c = Serial.read();
count++;
id += c;
if (count == 12)
{
String v = "AB123456789B";

  Serial.print(id);

  if (id == v)
  {
    Serial.print(id);
    Serial.println("First Valid Tag");

    char cc = Serial.read();

    if ( v == cc) {
      Serial.println("Enter other id");
    }
  }
  else if (id == "DB123456789C") {
    Serial.println("Second valid tag");
  }
  else
  {
    Serial.println("no tag");
  }
}

}
count = 0;
id = "";
delay(500);
}

[UKHeliBob]

Please follow the advice given in the link below when posting code. Use code tags (the </> icon above the compose window) to make it easier to read and copy for examination

How to get the best out of this forum

Hello, Welcome to the Arduino Forum. This guide explains how to get the best out of this forum. Please read and follow the instructions below. Being new here you might think this is having rules for the sake of rules, but that is not the case. If you don’t follow the guidelines all that happens is there is a long exchange of posts while we try to get you to tell us what we need in order to help you, which is frustrating for you and frustrating for us. The people who try to help with your pro…

[ToddL1962]

This will never be equal:

        char cc = Serial.read();

        if ( v == cc) {
          Serial.println("Enter other id");
        }

V is type String and cc is a single char.

[johnwasser]

It looks like you want two 12-character ID's entered in order.

String id;

const char *IDList[] = {"AB123456789B", "DB123456789C"};
int IDCount = 0;

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

void loop()
{
  while (Serial.available() > 0)
  {
    char c = Serial.read();
    id += c;
    if (id.length() == 12)
    {
      // We have a complete tag ID.
      // Check it against the current ID
      if (id == IDList[IDCount])
      {
        Serial.print("Valid match for ");
        Serial.println(IDList[IDCount]);
        IDCount++;
        id = "";

        if (IDCount == 2)
        {
          // All ID's matched.  What do you want to do?
          Serial.println("All tags matched.");
          IDCount = 0;
        }
      }
      else
      {
        // Does not match
        Serial.print(id);
        Serial.print(" is not a match for ");
        Serial.println(IDList[IDCount]);
        id = "";
      }
    }
  }
}