Arduino String Character Functions Code

The String functions charAt() and setCharAt() are used to get or set the value of a character at a given position in a String.

At their simplest, these functions help you search and replace a given character. For example, the following replaces the colon in a given String with an equals sign:

String reportString = “SensorReading: 456”;
int colonPosition = reportString.indexOf(‘:’);
reportString.setCharAt(colonPosition, ‘=’);

Here’s an example that checks to see if the first letter of the second word is ‘B’:

Arduino String Character Functions

String reportString = “Franklin, Benjamin”;
int spacePosition = reportString.indexOf(‘ ‘);
if (reportString.charAt(spacePosition + 1) == ‘B’) {
Serial.println(“You might have found the Benjamins.”)

Caution: If you try to get the charAt or try to setCharAt() a value that’s longer than the String’s length, you’ll get unexpected results. If you’re not sure, check to see that the position you want to set or get is less than the string’s length using the length() function.


There is no circuit for this example, though your Arduino must be connected to your computer via USB.

image developed using Fritzing. For more circuit examples, see the Fritzing project page


String charAt() and setCharAt()

Examples of how to get and set characters of a String

created 27 July 2010
modified 2 Apr 2012
by Tom Igoe

This example code is in the public domain.

Major Components in Project

Hardware Required:

  • Arduino Board

For more detail: Arduino String Character Functions Code

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