May 2009
Intermediate to advanced
510 pages
15h
English
Content preview from Regular Expressions Cookbook
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Chapter 7. URLs, Paths, and Internet Addresses
Along with numbers, which were the subject of the previous chapter, another major subject that concerns a wide range of programs is the various paths and locators for finding data:
URLs, URNs, and related strings
Domain names
IP addresses
Microsoft Windows file and folder names
The URL format in particular has proven so flexible and useful that it has been adopted for a wide range of resources that have nothing to do with the World Wide Web. The toolbox of parsing regular expressions in this chapter will thus prove valuable in a surprising variety of situations.
7.1. Validating URLs
Problem
You want to check whether a given piece of text is a URL that is valid for your purposes.
Solution
Allow almost any URL:
^(https?|ftp|file)://.+$
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python |
\A(https?|ftp|file)://.+\Z
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby |
Require a domain name, and don’t allow a username or password:
\A # Anchor (https?|ftp):// # Scheme [a-z0-9-]+(\.[a-z0-9-]+)+ # Domain ([/?].*)? # Path and/or parameters \Z # Anchor
| Regex options: Free-spacing, case insensitive |
| Regex flavors: .NET, Java, PCRE, Perl, Python, Ruby |
^(https?|ftp)://[a-z0-9-]+(\.[a-z0-9-]+)+↵ ([/?].+)?$
| Regex options: Case insensitive |
| Regex flavors: .NET, Java, JavaScript, PCRE, Perl, Python, Ruby |
Require a domain name, and don’t allow a username or password. Allow the scheme (http or ftp) to be omitted ...
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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.