C Tutorial/string.h/strspn
strspn
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;
}