C++ libcurl console progress bar

Question

I would like a progress bar to appear in the console window while a file is being downloaded. My code is this: http://stackoverflow.com/questions/1636333/download-file-using-libcurl-in-c-c/1636827#1636827.

How to have a progress bar in libcurl?

Answer 1

From the curl documentation

CURLOPT_PROGRESSFUNCTION

Function pointer that should match the curl_progress_callback prototype found in . This function gets called by libcurl instead of its internal equivalent with a frequent interval during operation (roughly once per second) no matter if data is being transfered or not. Unknown/unused argument values passed to the callback will be set to zero (like if you only download data, the upload size will remain 0). Returning a non-zero value from this callback will cause libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK.

So:

You provide a function that looks like this

int progress_func(void* ptr, double TotalToDownload, double NowDownloaded, double TotalToUpload, double NowUploaded)
{
    // It's here you will write the code for the progress message or bar
}

And some extra options after the existing options

curl_easy_setopt(curl, CURLOPT_WRITEDATA, fp);  // already there
// Internal CURL progressmeter must be disabled if we provide our own callback
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, FALSE);
// Install the callback function
curl_easy_setopt(curl, CURLOPT_PROGRESSFUNCTION, progress_func);

That's all that needs to be done

Answer 2

Your meter.

int progress_func(void* ptr, double TotalToDownload, double NowDownloaded, 
                    double TotalToUpload, double NowUploaded)
{
    // how wide you want the progress meter to be
    int totaldotz=40;
    double fractiondownloaded = NowDownloaded / TotalToDownload;
    // part of the progressmeter that's already "full"
    int dotz = round(fractiondownloaded * totaldotz);

    // create the "meter"
    int ii=0;
    printf("%3.0f%% [",fractiondownloaded*100);
    // part  that's full already
    for ( ; ii < dotz;ii++) {
        printf("=");
    }
    // remaining part (spaces)
    for ( ; ii < totaldotz;ii++) {
        printf(" ");
    }
    // and back to line begin - do not forget the fflush to avoid output buffering problems!
    printf("]\r");
    fflush(stdout);
}