STRNSTR(9) Kernel Developer's Manual STRNSTR(9)

strnstrlocate a substring in a string

#include <lib/libkern/libkern.h>

char *
strnstr(const char *big, const char *little, size_t len);

The () 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.

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);


December 21, 2023 OpenBSD 7.5