strspn : strspn « string.h « C Tutorial

Item	Value
Header file	string.h
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;
  }

24.19.strspn
	24.19.1.	strspn