strstr

   strstr 库函数用于找子串。

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

char *strstr_test(const char *s1, const char *s2);

int
main(int argc, char **argv)
{
    char *s1 = "hello andy haha";
    char *s2 = "andy";

    printf("Result: %s\n", strstr_test(s1, s2));

    return 0;
}

char *
strstr_test(const char *s1, const char *s2)
{
    size_t l1, l2;

    l2 = strlen(s2);
    if (!l2) {
        return (char *)s1;
    }
    l1 = strlen(s1);

    while (l1 >= l2) {
        l1--;
        if (!memcmp(s1, s2, l2)) {
            return (char *)s1;
        }
        s1++;
    }

    return NULL;
}