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Slice string at ":"

I need to slice a string (eg- 4:288:18464:288:4) at ":" into an array({4, 288, 18464, 288, 4}) I used the following code, but its giving only '4' in the serial monitor when "4:288:18464:288:4," is given to arduino.

void displayString(char* s)
{
 char* text = strtok(s,":");
 while(text != NULL){
 text = strtok(NULL,":");}
}
void loop()
{
 if(Serial.available() > 0)
 {
 str = Serial.readStringUntil(',');
 str.toCharArray(text,99);
 }
 displayString(text);
Serial.println(text);
}

Answer*

You don't use `strtok` the way it should:

 char* text = strtok(s,":");
 while(text != NULL){
 text = strtok(NULL,":");
 }

Your code just replaces, in `s`, all occurrences of `:` with `0` (i.e. a byte of value 0, not the ASCII value of `'0'`), thus terminating each substring.

At the end of `displayString(text)` call from `loop()`, `text` still points to the 1st character of the original string (in your post `4:288:18464:288:4`), but that string now terminates at the position of the first `:`, which explains why `Serial.println(text)` prints just `4`.

Now if you want to split the original string into an array of substrings, as asked in your question, you need to modify `displayString` this way:

 // Maximum number of substrings expected
 const int MAX_SUBSTRINGS = 5;
 // Array of pointers to each substring after displayString() has been called
 static char* substrings[MAX_SUBSTRINGS];
 
 void displayString(char* s) {
 // First clear the array of substrings
 for (int i = 0; i < MAX_SUBSTRINGS; i++)
 substrings[i] = 0;
 // Now split the input string
 char* text = strtok(s,":");
 int i = 0;
 while (text != 0 && i < MAX_SUBSTRINGS) {
 // A toekn was found: append it to the array of substrings
 substrings[i++] = text;
 text = strtok(0,":");
 }
 }

After calling `displayString(text)`, you can use its result in `loop()` as follows:

 void loop()
 {
 if (Serial.available() > 0)
 {
 str = Serial.readStringUntil(',');
 str.toCharArray(text,99);
 }
 displayString(text);
 for (int i = 0; i < MAX_SUBSTRINGS; i++) {
 if (substrings[i] != 0)
 Serial.println(substrings[i]);
 }
 }

Note that this will work **ONLY** if the original string contains no more than 5 substrings delimited by `:`. If the max number of substrings cannot be known at compile time, then you'll have to use dynamic allocation, [which is generally not a very good idea on embedded platforms][1].


 [1]: https://arduino.stackexchange.com/questions/682/is-using-malloc-and-free-a-really-bad-idea-on-arduino/687#687

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