C/string.h/strspn

strspn: returns the index of the first character in *str1 that does not match any of the characters in *str2

<source lang="cpp">

//Declaration: size_t strspn(const char *str1, const char *str2); //Return: returns the index of the first character in *str1 that does not match any of the characters in *str2.

 #include <string.h>
 #include <stdio.h>
 int main(void)
 {
   int len;
   len = strspn("this is a test", "hi");
   printf("%d", len);
   return 0;
 }
        

/* 0*/

      </source>