Question

I have a function (in C) that is passed a URL. This function only works if the URL parameter is in the form of www.example.com, not when it is http://www.example.com.

I would like to modify this function so that, when passed a URL in the form of http://www.example.com, it strips the leading http:// (if present), so that it will operate correctly.

How would I do this in C?

Here’s the function in question (let me know if there is a better way to do this):

char* get_ip (char* url)
{
    struct hostent* h;
    if ((h = gethostbyname(url)) == NULL)
        return NULL;

    return inet_ntoa(*((struct in_addr*)h->h_addr));
}

Answer 1

There’s always the simple approach:

char *url;
// ...
const char *http = "http://";
if (!strncmp(url, http, strlen(http)))
    url += strlen(http);

Or, if you want to get rid of protocol specifiers of that form in general (e.g., https):

char *url;
char *p = strstr(url, "://");
if (p)
    url = p + 3; // skip past :// part of URL