C语言 strcspn()函数

size_t strcspn(const char *str1, const char *str2)

#include <stdio.h>
#include <string.h>
int main () {
   const char str[20] = "aabbccddeeff"; 
   const char searchString[10] = "dxz";
   int loc;

   /* This function returns the number of characters present in the main string 
    * from beginning till the first matched character is found 
    */
   loc = strcspn(str, searchString);
   printf("The first matched char in string str1 is at: %d", (loc+1));
   return 0;
}

The first matched char in string str1 is at: 7