Linux

 while (cgiFormFileRead(file, b, sizeof(b), &got_count) == cgiFormSuccess)
        {
        fptr = fopen("progress_bar.txt", "w");
        fwrite(b,sizeof(char),got_count,output);
        i++;
                if(i == inc && j<=100)
                {
                fprintf(fptr, "%d" ,j);
                fseek(fptr, 0, SEEK_SET);
                i = 0;
                //fflush(fptr);
                fclose(fptr);
                j++;
                }
        }

function send_request()
{
request.onreadystatechange = request_handler;   
request.open("GET","progress_bar.txt",true);    //true means that Ajax will get data asynchronously
request.send(null);
}
function request_handler() //function to check if data is available for read
{
if (request.readyState == 4 && request.status == 200)
        {
        document.getElementById("progress").innerHTML= request.responseText + '%';
        document.getElementById("progress").style.width = request.responseText + '%';
        document.getElementById("progress").style.backgroundColor = "green";
         }
}