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substring()This tutorial will discuss splitting a string using the function in Arduino .

substring()Splitting a string in Arduino using the function

Arduino provides an inbuilt function substring()to split a given string. We can split the string using the start and end index values.

substring()The function takes two parameters. The first parameter is the starting index value from where we want to start the splitting process and the second parameter is the ending index value at which the splitting process will stop.

grammar:

Sub_string = MyString.substring(from, to);

The variable Sub_stringwill contain substring()the output of the function, while MyStringthe variable will contain the original string we want to split. fromThe variable contains the starting index, and tothe variable contains the ending index.

Let's define a string and substring()split it using the function and then print it on the Arduino's serial monitor.

example:

String My_S = "hello world";

void setup() { Serial.begin(9600); }
void loop() {
  String sub_S = My_S.substring(0, 5);
  Serial.println(sub_S);
  delay(1000);
}

Output:

hello

In the above code, Serial.println()the function prints the result on the serial monitor of Arduino. The string split will start at 0, including the 0 index character, and end at index 5, excluding the character at index 5.

We can also indexOf()find the character index using Arduino's index function. The index function accepts two parameters.

The first parameter is mandatory and indicates the character or string whose index we want to find. The second parameter is optional and it indicates the starting index from which to find the character index.

By default, indexOf()the function searches the string from the beginning to find the index of a given character, but we can also indexOf()pass an index as a starting point using the second argument of the function.

grammar:

int index = MyString.indexOf(val, from);

indexThe variable will store valthe variable index which contains the character or string in the above code. fromThe variable defines the starting index which is used as the starting point to find the given character index.

substring()We use the function when we don't know the index of the character to pass into indexOf().

For example, if we want to split a given string using the space character as the ending index, we can use indexOf()the function to find the index of the space character and then substring()use it in the function to split the string.

If the index is not found in the given string, indexOf()the function will return -1.

example:

String My_S = "hello world";

void setup() { Serial.begin(9600); }
void loop() {
  int index = My_S.indexOf(' ');
  String sub_S = My_S.substring(0, index);
  Serial.println(index);
  Serial.println(sub_S);
  delay(1000);
}

Output:

5
hello

In the above code, the variable indexcontains the index of the space character present in the given string. As you can see, we display the index and the result of the string split on the serial monitor window.

We can also split the string based on the number of lines.

For example, if a string contains multiple lines of text, we want to split and treat each line as a separate string.

We can use indexOf('\n')the function to find the index of the new line and split the given string accordingly.

indexOf()The function starts searching for the index from the beginning of the given string. However, we can also use lastIndexOf()the function, which starts searching for the index from the end of the string.

As a second parameter, we can also lastIndexOf()pass the starting index in the function. For example, let's split a string containing three lines, get the last line, and display it on the serial monitor window.

example:

String My_S = "hello world\nGreetings\nPeople";

void setup() {
  Serial.begin(9600);
  Serial.println(My_S);
}
void loop() {
  int index = My_S.lastIndexOf('\n');
  int length = My_S.length();
  String sub_S = My_S.substring(index, length);
  Serial.println(sub_S);
  delay(100000);
}

Output:

hello world
Greetings
People

People

We have used the split function in the above code lastIndexOf()because we only want to get the last line of text present in the given string. The first three lines are the given string in the output and the fourth line is the result of the string split.

We use length()the function to get the length of the given string, which will be used as substring()the ending index value in . We use delay()the function to add some delay in the code execution as the loop will repeat the process.

If we only want to do the splitting, we can setup()write the code in a function, which will only run once.

We can split a string based on any character. We just need to indexOf()find its index using the split_string function.

We can substring()split a string using the split function. Suppose we want to get all the lines in a given string separately. We have to get one line, save the remaining string in a variable, and then do the same thing again using a loop until all the lines are extracted.