A general question

Hi there and hello to all,

I was just wondering if it is possible to access an online file posted on a website thru C codes. I mean if we are using, lets say, Microsoft Visual C++, is there any commands to read a line from a txt file posted on http://www.cprogramming.com/test.txt (for example) ???

I'd appreciate to hear from you or any extra info that you might have.

Tanx.

there are platform specific ways to do it, with windows you would use winsock or one of the wrapper classes, for instance wininet api, look into using that.

Code:

---

#include <windows.h>
#include <wininet.h>

#pragma comment(lib, "winInet.lib")

#define MAX_INTERNETFILE_LENGTH 20480

char* DownloadFile(char* strURL,HWND hwnd)
{
        BYTE data[MAX_INTERNETFILE_LENGTH];

        HINTERNET hInternet=NULL;
        hInternet=InternetOpen("agent name",INTERNET_OPEN_TYPE_DIRECT,NULL,NULL,0);
        HINTERNET hOpenURL=InternetOpenUrl(hInternet,strURL,NULL,0,INTERNET_FLAG_DONT_CACHE,0);

        DWORD dwSize=0;
        DWORD dwOffset=0;
        DWORD dwNumBytesRead=0;
        BOOL returnValue=TRUE;

        char* vData=(char*)malloc(1);
        while(returnValue)
        {
                returnValue=InternetReadFile(hOpenURL,(VOID*)data,MAX_INTERNETFILE_LENGTH,&dwNumBytesRead);
                if(!dwNumBytesRead)
                {
                        if(!returnValue)
                                MessageBox(hwnd,"Error downloading file.","Error",MB_OK);
                        break;
                }
                dwSize+=dwNumBytesRead;
                vData=(char*)realloc((void*)vData,dwSize+1);
                memcpy(vData+dwOffset,(void*)data,dwNumBytesRead);
                dwOffset+=dwNumBytesRead;
        }

        *(vData+dwOffset)='\0';

        InternetCloseHandle(hOpenURL);
        InternetCloseHandle(hInternet);

        return vData;
}

---

Won't return until all data has been downloaded for that file. It returns (as a char*) the data for the file, which you must delete when done with.

Windows-specific, mind you.

Thanks for the code.

Although I couldn't use the function and got so many errors that couldn't fix. :(

Are you using a Windows compiler?

Code:

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char* vData=(char*)malloc(1);

---

You shouldn't cast malloc(). And you should free() the memory when you're done with it.

Quote:

---

I couldn't use the function and got so many errors that couldn't fix.

---

With that function, or the rest of the code?

Yes, I am using a windows compiler. (MS Visual)

When i try to compile this code, i get 23 errors. the only one that I can fix is in this line:

Code:

---

HINTERNET hOpenURL=InternetOpenUrl(hInternet,strURL,NULL,0,I  NTERNET_FLAG_DONT_CACHE,0);

---

As you see there is a space between 'I' and 'NTERNET' so:

Code:

---

HINTERNET hOpenURL=InternetOpenUrl(hInternet,strURL,NULL,0,INTERNET_FLAG_DONT_CACHE,0);

---

which reduces the errors to 19. but about the rest, I have no idea. and unsure when to free the malloc. (right at the end, before 'return' wouldn't cause a problem would it?)

Do you #include <windows.h>?

Yes, I do include <windows.h> . The first line of the code.