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From: Robert Klemme <shortcutter@googlemail.com>
Newsgroups: comp.lang.ruby
Subject: Re: *Could use some help here* Ruby script that downloads .png files that   are ordered in sequence and saves them locally.
Date: Fri, 08 Feb 2013 08:23:47 +0100
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On 07.02.2013 23:36, patrick.anthony124@gmail.com wrote:
> Hey everyone. This is the first time I've written something in Ruby to do something for myself, everything else has been some how part of an assignment or a tutorial or a walk-through. I want this script to download a series of .png files and save them locally in the same order. I have posted it below but it just doesn't seem to work. Any help or suggestions would be greatly appreciated.
>
> require "net/http"
> remote_base_url = "https://path.to/the/folder"
>
> start_page = 001
> end_page = 281

The reason is probably that you use integers here.  Note:

irb(main):001:0> x = 001
=> 1
irb(main):002:0> puts x
1
=> nil

Leading zeros are removed.

If you use that (and I would recommend using integers here) you must 
ensure the zeros are added when creating URLs:

> # Images are named p001.png to p281.png.
> (start_page..end_page).each do |it|
>      rpage = open(remote_base_url + "/" + "p" + it.to_s)

# example:
rpage = open(sprintf("%s/p%0d", remote_base_url, it))

>      local_fname = "copy-of-" + it.to_s + ".png"

# other approach
local_fname = "copy-of-%03d.png" % it

>      local_file = open(local_fname, "w")
>      local_file.write(rpage.read)
>      local_file.close
>     # Optional output line:
>     puts "Wrote file " + local_fname
>     sleep 1

Why the sleep?

> end
>
> # Write to the compiled file now:
> compiled_file = open(start_page.to_s + "-" + end_page.to_s + ".png",  "w")
> (start_page..end_page).each do |it|
>      local_fname = "copy-of-" + it.to_s + ".png"
>      local_file = open(local_fname, "r")
>
>      compiled_file.write(local_file.read)
>      local_file.close
> end
>
> compiled_file.close

And a general remark: you should use the block form of #open instead of 
the explicit #close call.  This is much more robust because it ensures 
files are always closed.  See my blog post for more details

http://blog.rubybestpractices.com/posts/rklemme/002_Writing_Block_Methods.html

Kind regards

	robert


-- 
remember.guy do |as, often| as.you_can - without end
http://blog.rubybestpractices.com/