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String substring Function
The String function substring() is closely related to charAt(), startsWith() and endsWith(). It allows you to look for an instance of a particular substring within a given String.
Hardware Required
- Arduino Board
Circuit
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
Code
substring() with only one parameter looks for a given substring from the position given to the end of the string. It expects that the substring extends all the way to the end of the String. For example:
// substring(index) looks for the substring from the index position to the end:
if (stringOne.substring(19) == "html") {
}
// substring(index) looks for the substring from the index position to the end:
if (stringOne.substring(19) == "htm") {
}
l after the htm in the String.
substring() with two parameters looks for a given substring from the first parameter to the second. For example:
// you can also look for a substring in the middle of a string:
if (stringOne.substring(14,18) == "text") {
}
This looks for the word text from positions 14 through 18 of the String.
Caution:
make sure your index values are within the String's length or you'll get unpredictable results. This kind of error can be particularly hard to find with the second instance of substring() if the starting position is less than the String's length, but the ending position isn't.
String substring()
Examples of how to use substring in a String
created 27 July 2010
by Tom Igoe
http://arduino.cc/en/Tutorial/StringSubstring
This example code is in the public domain.
*/
void setup() {
Serial.begin(9600);
Serial.println("\n\nString substring():");
}
void loop() {
// Set up a String:
String stringOne = "Content-Type: text/html";
Serial.println(stringOne);
// substring(index) looks for the substring from the index position to the end:
if (stringOne.substring(19) == "html") {
Serial.println("It's an html file");
}
// you can also look for a substring in the middle of a string:
if (stringOne.substring(14,18) == "text") {
Serial.println("It's a text-based file");
}
// do nothing while true:
while(true);
}