August 2012
Intermediate to advanced
609 pages
19h 16m
English
Content preview from Regular Expressions Cookbook, 2nd Edition
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8.8. Extracting the Scheme from a URL
Problem
You want to extract the URL scheme from a string that
holds a URL. For example, you want to extract http from http://www.regexcookbook.com.
Solution
Extract the scheme from a URL known to be valid
^([a-z][a-z0-9+\-.]*):
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Extract the scheme while validating the URL
\A ([a-z][a-z0-9+\-.]*): (# Authority & path // ([a-z0-9\-._~%!$&'()*+,;=]+@)? # User ([a-z0-9\-._~%]+ # Named host |\[[a-f0-9:.]+\] # IPv6 host |\[v[a-f0-9][a-z0-9\-._~%!$&'()*+,;=:]+\]) # IPvFuture host (:[0-9]+)? # Port (/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/? # Path |# Path without authority (/?[a-z0-9\-._~%!$&'()*+,;=:@]+(/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?)? ) # Query (\?[a-z0-9\-._~%!$&'()*+,;=:@/?]*)? # Fragment (\#[a-z0-9\-._~%!$&'()*+,;=:@/?]*)? \Z
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby |
^([a-z][a-z0-9+\-.]*):(//([a-z0-9\-._~%!$&'()*+,;=]+@)?([a-z0-9\-._~%]+|↵ \[[a-f0-9:.]+\]|\[v[a-f0-9][a-z0-9\-._~%!$&'()*+,;=:]+\])(:[0-9]+)?↵ (/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?|(/?[a-z0-9\-._~%!$&'()*+,;=:@]+↵ (/[a-z0-9\-._~%!$&'()*+,;=:@]+)*/?)?)(\?[a-z0-9\-._~%!$&'()*+,;=:@/?]*)?↵ (#[a-z0-9\-._~%!$&'()*+,;=:@/?]*)?$
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python |
Discussion
Extracting the scheme from a URL is easy if you already know that your subject text is a valid URL. A URL’s scheme always occurs at the very start of the ...
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.