Code:
#include <stdio.h>
#include <string.h>
char *substring (char *string, char *sub) {
int stl=strlen(string), sbl=strlen(sub), i, n;
char chunk[sbl+1], *ptr;
for (i=0;i<stl;i++) {
if (sbl+i > stl) return NULL;
for (n=0;n<sbl;n++) chunk[n]=string[i+n];
chunk[n]=0;
if (strcmp(sub,chunk) == 0) {return (char*)string+i;}
}
return NULL;
}
int main() {
char string[64], sub[64], *ptr;
printf("Enter a string: ");
fgets(string,63,stdin);
printf("Enter a substring: ");
fgets(sub,63,stdin);
sub[strlen(sub)-1]=0; // remove newline
ptr=substring(string,sub);
if (ptr != NULL) printf("%s\n",ptr);
}