Replicate the standard string library function strstr().

#include <stdio.h>

int fnsubstr(char *, char *);

int main(void)
{
char str1[40], str2[40];
int val;

printf("\nEnter a string : ");
gets(str1);
printf("\nEnter a search string : ");
gets(str2);

val = fnsubstr(str1, str2);

if(val == 0)
printf("\n[%s] occurs in [%s]", str2, str1);
else
printf("\n[%s] does not occur in [%s]", str2, str1);

return 0;
}

int fnsubstr(char *src, char *str)
{
int x, y;
for(x = 0 ; src[x] != '\0' ; x++)
{
for(y = 0 ;
str[y] != '\0' && src[x + y] != '\0' && str[y] == src[x + y] ;
y++);

if(str[y] == '\0')
return 0;
}
return 1;
}