From: Rob Biedenharn <Rob@...>
Date: 2009-01-05T06:58:04+09:00
Subject: Re: Finding filename from a URL


On Jan 4, 2009, at 4:44 PM, Robert Klemme wrote:

> On 04.01.2009 21:46, Rob Biedenharn wrote:
>> On Jan 4, 2009, at 1:04 PM, Robert Klemme wrote:
>>> On 04.01.2009 17:29, Sam Fent wrote:
>>>> This is just a basic parsing question, really. I'm trying to work  
>>>> out
>>>> how I would process a URL such as
>>>> "http://www.example.com/x/y/z/myfile.txt" and get back the filename
>>>> "myfile". Basically the pattern is to get the past part of the  
>>>> string
>>>> after the final /, and then strip off the filetype.
>>> IMHO it is not a good idea to use a File method for URL's because   
>>> File.basename has different criteria
>>>
>>> irb(main):003:0> File.basename 'http://test.com/aaa\\bbb.txt'
>>> => "bbb.txt"
>>>
>>> Although I am not sure whether a backslash is allowed there, this  
>>> is  what I'd do:
>>>
>>> irb(main):001:0> url = 'http://www.example.com/x/y/z/myfile.txt'
>>> => "http://www.example.com/x/y/z/myfile.txt"
>>> irb(main):002:0> name = url[%r{[^/]+\z}]
>>> => "myfile.txt"
>> Rather than jump to a Regexp, just use the right tool for the job.
>> irb> require 'uri'
>> => true
>> irb> u=URI.parse 'http://www.example.com/x/y/z/myfile.txt'
>> => #<URI::HTTP:0x1cac14 URL:http://www.example.com/x/y/z/myfile.txt>
>> irb> u.path
>> => "/x/y/z/myfile.txt"
>> irb> File.basename u.path, '.txt'
>> => "myfile"
>
> I considered URI as well but what makes your code the "right tool  
> for the job"?  Basically you use URI only to extract the path and  
> then use File.basename to get the last bit of the path.  But: while  
> the URI path consists of elements separated by "/", File.basename  
> also considers "\\" as delimiter.  So IMHO it is by no means "the  
> right tool" - at least not more than using a regular expression  
> which extracts exactly the part needed from the string at hand (and  
> is likely faster as well).
>
> The situation would be different if URI provided a method which  
> returns the last path element but as far as I can see this does not  
> exist.
>
> Kind regards
>
> 	robert


I guess it depends on what your url might look like. For example, if  
it contains a query string:

irb> str = 'http://a.b.c/root/sub/dir/file?param=a'
=> "http://a.b.c/root/sub/dir/file?param=a"
irb> File.basename str
=> "file?param=a"

Oops!  File.basename just doesn't fit.

irb> require 'uri'
=> true
irb> url = URI.parse(str)
=> #<URI::HTTP:0x1c8446 URL:http://a.b.c/root/sub/dir/file?param=a>
irb> url.path
=> "/root/sub/dir/file"
irb> File.basename url.path
=> "file"

The OP will have to make the final tool selection, but there may be  
lurkers that have similar problems who find URI a better fit than File.

-Rob

Rob Biedenharn		http://agileconsultingllc.com
Rob@AgileConsultingLLC.com