C programming arrays?

[matt d]

Hi guys,

I'm writing a function that will replace the last occurrence of a character in a string. Although, it seems to replace all the characters in the string. This is what i have so far:

char s[] = hello123

old = l

new = b

void replace_last(char s[], int old, int new) {
size_t i;
size_t index = 0;

while(s[index] == old){
index++;
}

for(i=0; s[i] != '{rss:Content}'; i++){
if(s[i+index] == old){
s[i+index] = new;
}
}
}

So i'm trying to get the output of 'helbo123' but instead I get 'hebbo123'.

Anyone care to elaborate on this? Any help would be appreciated.
hmm sorry, i should have added that i'm trying to do it without any standard library functions. Thanks
(other than stdio.h)
actually, I just figured out a way without using strlen from That Guy's example. Thanks