Help with strings

that said, an extension need not be 3 letters. (You can use strrchr to find the last "." in a string -- check it for NULL if there is no dot). On the whole, you should be very careful when using C style strings. If at all possible, use C++ style strings. And never trust any user input!

I assume you are using C, not C++, because in C++, you'd be using std::string instead of an array of characters.

#include <stdio.h>#include <string.h>int bmp2lua(char *filename){    char *extension = filename + strlen(filename) - 4;    if (extension < filename || strcmp(extension, ".bmp")) return -1;    strcpy(extension, ".lua");    return 0;}int main(void){    char FileName[100] = "Filename.bmp";    bmp2lua(FileName);    printf("%s\n", FileName);    return 0;}