How to split a string by another string in Arduino?

The main problem is that strtok does not find a string inside another string. strtok looks for a character in a string. When you give multiple characters to strtok it looks for any of these. Consequently, writing strtok(array, "..."); is exactly the same as writing strtok(array, ".");. That is why you get a split after "3."

There are multiple ways of doing what you want. Below I'll show you an example using strstr. Unlike strtokthe strstr function do find a substring inside a string - just what you are looking for. But.. strstr is not a tokenizer so some extra code is required to print the substrings.

Something like this should do:

int main()
{
  char array[] = "AAAA... A1... 3. B1...";

  char* ps = array;
  char* pf = strstr(ps, "..."); // Find first substring
  while(pf)
  {
    int len = pf - ps;          // Number of chars to print
    printf("%.*s\n", len, ps);
    ps = pf + 3;
    pf = strstr(ps, "...");     // Find next substring
  }
  return 0;
}

You can implement your own split as strtok except the role of the second argument :

#include <stdio.h>
#include <string.h>

char * split(char *str, const char * delim)
{
  static char * s;
  char * p, * r;

  if (str != NULL)
    s = str;

  p = strstr(s, delim);

  if (p == NULL) {
    if (*s == 0)
      return NULL;

    r = s;
    s += strlen(s);
    return r;
  }

  r = s;
  *p = 0;
  s = p + strlen(delim);

  return r;
}

int main()
{
  char s[] = "AAAA... A1... 3. B1.";
  char * p = s;
  char * t;

  while ((t = split(p, "...")) != NULL) {
    printf("'%s'\n", t);
    p = NULL;
  }

  return 0;
}

Compilation and execution:

/tmp % gcc -g -pedantic -Wextra s.c
/tmp % ./a.out
'AAAA'
' A1'
' 3. B1.'
/tmp % 

I print between '' to show the return spaces, because I am not sure you want them, so delim is not only ... in that case

Because you tagged this as c++, here is a c++ 'version' of your code:

#include <iostream>
using std::cout;
using std::endl; 

#include <vector>
using std::vector;

#include <string>
using std::string;


class T965_t
{
   string         array;
   vector<string> strings;

public:
   T965_t() : array("AAAA... A1... 3. B1.") 
      {
         strings.reserve(10);
      }

   ~T965_t() = default;

   int operator()() { return setup(); } // functor entry

private: // methods

   int setup()
      {
         cout << endl;
         const string pat1 ("... ");
         string s1 = array; // working copy

         size_t indx = s1.find(pat1, 0); // find first ... pattern
         // start search at ---------^
         do
         {
            if (string::npos == indx)  // pattern not found
            {
               strings.push_back (s1); // capture 'remainder' of s1
               break;                  // not found, kick out
            }

            // else 
            // extract --------vvvvvvvvvvvvvvvvv
            strings.push_back (s1.substr(0, indx));  // capture
            // capture to vector

            indx += pat1.size(); // i.e. 4

            s1.erase(0, indx); // erase previous capture 

            indx = s1.find(pat1, 0);          // find next

         } while(true);

         for(uint n = 0; n < strings.size(); n++)
            cout << strings[n] << "\n";

         cout << endl;
         return 0;
      }

}; // class T965_t

int main(int , char**) { return T965_t()(); } // call functor

With output:

AAAA
A1
3. B1.

Note: I leave changing "3. B1." to "3.B1.", and adding commas at end of each line (except the last) as an exercise for the OP if required.

I looked for a split function and I didn't find one that meets my requirement, so I made one and it works for me so far, of course in the future I will make some improvements, but it got me out of trouble.

But there is also the strtok function and better use that. https://www.delftstack.com/es/howto/arduino/arduino-strtok/

I have the split function

Arduino code:

void split(String * vecSplit, int dimArray,String content,char separator){
if(content.length()==0)
    return;
 content = content + separator;
 int countVec = 0;
 int posSep = 0;
 int posInit = 0;
 while(countVec<dimArray){
   posSep = content.indexOf(separator,posSep);
   if(posSep<0){
    return;
   } 
 countVec++;       
 String splitStr = content.substring(posInit,posSep);
 posSep = posSep+1; 
 posInit = posSep;
 vecSplit[countVec] = splitStr;
 countVec++;    

} }

Llamada a funcion:

smsContent = "APN:4g.entel;DOMAIN:domolin.com;DELAY_GPS:60";
String vecSplit[10];

split(vecSplit,10,smsContent,';');
for(int i = 0;i<10;i++){
   Serial.println(vecSplit[i]);    
}

String input: APN:4gentel;DOMAIN:domolin.com;DELAY_GPS:60

Output:

• APN:4g.entel
• DOMAIN:domolin.com
• DELAY_GPS:60
• RESET:true

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