regex to check url format [closed] - ruby

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I want to check if my url format is correct, it has some AWS acces keys etc:
/https://bucket.s3.amazonaws.com/path/file.txt?AWSAccessKeyId=[.+]&Expires=[.+]&Signature=[.+]/.match(url)
^ something like this. Could you please help?

Answer 1

URI RFC specifies this regular expression for parsing URLs and URIs:
^(([^:/?#]+):)?(//([^/?#]*))?([^?#]*)(\?([^#]*))?(#(.*))?
You can also use the URI module from Ruby standard library:
require 'uri'
if url =~ /^#{URI::regexp(%w(http https))}$/
puts "it's an url alright"
else
puts "that's no url, that's a spaceship"
end
To check for the existence of "some AWS access keys etc" you can do:
require 'uri'
uri = URI.parse(url)
params = URI.decode_www_form(uri.query).to_h
if params.has_key?('AWSAccessKeyId')
unless params['AWSAccessKeyId'] =~ /\A[a-f0-9]{32}\z/
abort 'AWSAccessKeyId not valid'
end
else
abort 'AWSAccessKeyId required'
end
Of course you can just use regular expressions to parse them directly but it gets ugly because the order of the parameters may be different:
>> url = "https://bucket.s3.amazonaws.com/path/file.txt?AWSAccessKeyId=abcd12345&Expires=12345678&Signature=abcd"
>> matchdata = url.match(
/
\A
(?<scheme>http(?:s)?):\/\/
(?<host>[^\/]+)
(?<path>\/.+)\?
(?=.*(?:[\?\&]|\b)AWSAccessKeyId\=(?<aws_access_key_id>[a-f0-9]{1,32}))
(?=.*(?:[\?\&]|\b)Expires=(?<expires>[0-9]+))
/x
)
=> #<MatchData "https://bucket.s3.amazonaws.com/path/file.txt?"
scheme:"https"
host:"bucket.s3.amazonaws.com"
path:"/path/file.txt"
aws_access_key_id:"abcd12345"
expires:"12345678">
>> matchdata[:aws_access_key_id]
# => "abcd12345"
This uses
The positive lookahead of regex : (?=..) to ignore parameter
order
Ruby's regex named captures (?<param_name>.*) to identify
the params from match data
Non capturing groupings (?abcd|efgh)
The matcher (?[\&\?]|\b) to handle Expires=..., ?Expires=... or &Expires=...
And finally the /x free spacing modifier to
allow nicer formatting

Answer 2

We need a url to work with:
url = "/https://bucket.s3.amazonaws.com/path/file.txt?AWSAccessKeyId=somestuff&Expires=somemorestuff&Signature=evenmorestuff"
We also need to escape a bunch of stuff and do some non-greedy matching(.+?):
/https:\/\/bucket.s3.amazonaws.com\/path\/file\.txt\?AWSAccessKeyId=.+?&Expires=.+?&Signature=.+/.match(url)
=> #<MatchData "https://bucket.s3.amazonaws.com/path/file.txt?AWSAccessKeyId=somestuff&Expires=somemorestuff&Signature=evenmorestuff">