String Character Functions

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':

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.

Hardware Required

  • Arduino Board


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.

Arduino bb

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


See Also

Last revision 2015/08/11 by SM