String startsWith and endsWith Functions

The String functions startsWith() and endsWith() allow you to check what character or substring a given String starts or ends with. They're basically special cases of substring.

Step 1: What You Need?

1 x Arduino Board ( Arduino UNO R3 used in this tutorial.)
1 x USB Type-B Cable 


Optional 

Arduino Uno R3 Acrylic Transparent Casing

Arduino Compatible UNO Ultimate Starter Kit / Learning Kit

Don't have components? Don't worry. Just click the component's name. 

Step 2: Build Your Circuit.

There is no circuit for this example, though your board must be connected to your computer via USB and the serial monitor window of the Arduino Software (IDE) should be open.

Step 3: Upload The Code.

1. Select the Arduino board type: Select Tools >> Board >> Select your correct Arduino board used.

2. Find the port number by accessing device manager on Windows. See the section Port (COM&LPT) and look for an open port named "Arduino Uno (COMxx)". If you are using a different board, you will find a name accordingly. What matters is the xx in COMxx part. In my case, it's COM3. So my port number is 3.

Select the right port: Tools >> Port >> Select the port number.

3. You can find this code in the example of Arduino IDE.

Select File >> Examples >> 08. Strings >> StringStartsWithEndsWith

Click press the "upload" button (see the button with right arrow mark).

startsWith() and endsWith() can be used to look for a particular message header, or for a single character at the end of a String. They can also be used with an offset to look for a substring starting at a particular position. For example: 

stringOne = "HTTP/1.1 200 OK";
  if (stringOne.startsWith("200 OK", 9)) {
    Serial.println("Got an OK from the server"); 
  } 

This is functionally the same as this:

stringOne = "HTTP/1.1 200 OK";
  if (stringOne.substring(9) == "200 OK") {
    Serial.println("Got an OK from the server"); 
  } 

Caution: If you look for a position that's outside the range of the string,you'll get unpredictable results. For example, in the example above stringOne.startsWith("200 OK", 16) wouldn't check against the String itself, but whatever is in memory just beyond it. For best results, make sure the index values you use for startsWith and endsWith are between 0 and the String's length().

Download:

Arduino IDE

Sources:https://www.arduino.cc/en/Tutorial/StringStartsWithEndsWith

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Author & Editor

My Robot Education Sdn. Bhd. (Robotedu.my) was founded in 2015 as the first robotics education centre in Malaysia to provide Arduino-based robotics courses for youths. Our vision is to be able to provide robotics education to every youth in Malaysia.