# Download a file piece by piece

**URL:** <https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807>\
**Category:** Ruby\
**Created:** [November 30, 2006, 6:08pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807 "2006-11-30T18:08:27Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![pjpatten](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e47c2d/32.png) [@pjpatten](https://www.ruby-forum.com/u/pjpatten)\
**Post date:** [November 30, 2006, 6:08pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807/1 "2006-11-30T18:08:27Z")

</div>

Hello people :-),

i have a question about downloading files. I want to download a file and  
print out how many bytes are downloaded. That’s important to me, because  
i want to have a progress bar later.

The problem is that it looks like my code downloads the whole file and  
after that it executes the while loop - this behavior is useless for me.

does anyone know how to fix it or knows a better solution?

Thanks,  
Patrick

A working example:

require ‘open-uri’

FILE\_BUFFER\_SIZE = 65536  
filename = “dailysourcecode-39523-11-30-2006.mp3”  
url =  
“[http://m-uk.podshow.com/media/21/episodes/39523/dailysourcecode-39523-11-30-2006.mp3](http://m-uk.podshow.com/media/21/episodes/39523/dailysourcecode-39523-11-30-2006.mp3)”

open(url, “r”) do |input|  
open(filename, “w”) do |output|  
bytes\_downloaded = 0  
while (buffer = input.read(FILE\_BUFFER\_SIZE))  
output.write(buffer)  
bytes\_downloaded += FILE\_BUFFER\_SIZE  
puts bytes\_downloaded  
end  
end  
end

---

<div class="post-metadata">

**Author:** ![pjpatten](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e47c2d/32.png) [@pjpatten](https://www.ruby-forum.com/u/pjpatten)\
**Post date:** [November 30, 2006, 7:02pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807/2 "2006-11-30T19:02:41Z")

</div>

On 11/30/06, Patrick P. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote:

> i have a question about downloading files. I want to download a file and  
> print out how many bytes are downloaded. That’s important to me, because  
> i want to have a progress bar later.

> The problem is that it looks like my code downloads the whole file and  
> after that it executes the while loop - this behavior is useless for me.

It would be nice if there was an easier way to handle the data as it  
comes in; but if you just need to do a progress bar, Kernel.open takes  
two optional parameters just for this purpose:

:content\_length\_proc - gets called initially w/ the document size, if it  
could be obtained in the content-length header

:progress\_proc - gets called with the size of the data read so far.

It’s in the rdoc for open-uri under OpenURI::OpenRead#open.

---

<div class="post-metadata">

**Author:** ![pjpatten](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e47c2d/32.png) [@pjpatten](https://www.ruby-forum.com/u/pjpatten)\
**Post date:** [November 30, 2006, 7:08pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807/3 "2006-11-30T19:08:42Z")

</div>

Patrick P. wrote:

> Hello people :-),
> 
> i have a question about downloading files. I want to download a file and  
> print out how many bytes are downloaded. That’s important to me, because  
> i want to have a progress bar later.
> 
> The problem is that it looks like my code downloads the whole file and  
> after that it executes the while loop -

No, actually, it is that the results are not printed out when you expect  
them to be. The code is running as you wrote it, but the result printing  
is  
being delayed. See below for the reason.

> this behavior is useless for me.
> 
> does anyone know how to fix it or knows a better solution?

This is a very common beginner problem. The issue is that the main  
thread of  
your application is too busy downloading the file to print anything out.  
After the file is completely downloaded, your code exits, which gives  
the  
environment freedom to do other things like print some data on the  
display.

To get a running account of your activity, you need to learn how to use  
threads, and even then, because of how Ruby handles threads, showing a  
progress bar is not a slam dunk.

---

<div class="post-metadata">

**Author:** ![pjpatten](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e47c2d/32.png) [@pjpatten](https://www.ruby-forum.com/u/pjpatten)\
**Post date:** [November 30, 2006, 8:49pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807/4 "2006-11-30T20:49:09Z")

</div>

Louis J Scoras schrieb:

> 

Thanks! I’m happy. It works really great 🙂

Have a nice day,  
Patrick

---

<div class="post-metadata">

**Author:** ![pjpatten](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/e47c2d/32.png) [@pjpatten](https://www.ruby-forum.com/u/pjpatten)\
**Post date:** [November 30, 2006, 7:40pm UTC](https://www.ruby-forum.com/t/download-a-file-piece-by-piece/77807/5 "2006-11-30T19:40:53Z")

</div>

We understand that you are very smart and have been programming for 30  
years, but if you don’t have anything constructive to add, like a  
reference  
to learning how to use threads, could you please quit cluttering my  
inbox  
with your rants? Does anyone else have visions of an old man waving his  
cane around screaming at the kids to get off his lawn?  
By the way, I like the ruby stuff on your web page, even if the vast  
majority is way over my head.