strcspn : strcspn « string.h « C Tutorial

Item	Value
Header file	string.h
Declaration	size_t strcspn(const char str1, const char str2);
Return	returns the index of the first character in str1 that matches any of the characters in str2.

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

  int main(void)
  {
    int len;
    len = strcspn("this is a test", "ab");
    printf("%d", len);

    return 0;
  }

24.11.strcspn
	24.11.1.	strcspn