Downloading a file via HTTP?

I'm looking for a simple example of how to download a file (HTML/image/whatever) from a site and provide a referrer.

I wrote this grabimage.c program last year that will download an image into a directory called /root/test if you give it the url of the image on the command-line. It also displays the header of the packet containing the image. (You may also need to look at the header file, mine.h, which is a bunch of generic functions only a few of which are used in grabimage.c)

Unfortunately, I didn't add much in the way of comments, but it may give you some idea of the complexities involved. It works this way:

• create a PF_INET socket and connect() to the remote server
• send a GET request for the image
• while receiving the response, watch for the "Content-Length:" line; this gives you the exact size of the image, and everything after that is the image itself.
• write the image to a local file

One complication I can recall is that your send/receive (or write/read) calls are not guaranteed to write or read as much as you want. This can be a screw up, particularly with the send, so you need to verify and complete the process:

Code:

int Transmit (int sock, char *line) {
        int done, todo=strlen(line);
        while (todo>0) {
                if ((done=send(sock,line,todo,0))==-1) return done;
                todo-=done;
                line+=done;
        }
        return 0;
}

This way, if send() only sent half of "line" on the first call, we loop around, advancing the "line" pointer appropriately, until the entire string has gone.

Just use Win32 api.
1 line of code.

Originally Posted by Alex31

Just use Win32 api.
1 line of code.

1 line? How's that work?

Code:

#include <windows.h>

int main(void) {
   DownloadFileToThisDirectoryNow("http://site.com/file.exe", "C:\\file");
   return 0;
}

I think he lied... I can't even do it in 1 line of code and I made up a Winapi function