strnstr.3bsd - Man Page

library “libbsd”

#include <string.h> (See libbsd(7) for include usage.)
char *
strnstr(const char *big, const char *little, size_t len);

The strnstr() function locates the first occurrence of the null-terminated string little in the string big, where not more than len characters are searched. Characters that appear after a ‘\0’ character are not searched. Since the strnstr() function is a FreeBSD specific API, it should only be used when portability is not a concern.

If little is an empty string, big is returned; if little occurs nowhere in big, NULL is returned; otherwise a pointer to the first character of the first occurrence of little is returned.

The following sets the pointer ptr to NULL, because only the first 4 characters of largestring are searched:

const char *largestring = "Foo Bar Baz";
const char *smallstring = "Bar";
char *ptr;

ptr = strnstr(largestring, smallstring, 4);

strstr(3), strcasestr(3), memchr(3), memmem(3), strchr(3), strcspn(3), strpbrk(3), strrchr(3), strsep(3), strspn(3), strtok(3), wcsstr(3)

The strnstr() function originated in FreeBSD.