whats wrong with my c++ boost regex function?

Question

include

#include <algorithm> #include<boost/algorithm/string.hpp> #include<boost/regex.hpp> using namespace std; using namespace boost; string _getBasehtttp(string url) { regex exrp( "^(?:http://)?([^\\/]+)(.*)$" ); match_results<string::const_iterator> what; if( regex_search( url, what, exrp ) ) { string base( what[1].first, what[1].second ); return base; } return ""; } int main( ) { cout << _getBasehtttp("httpasd://www.google.co.in"); }

if i input http://www.google.co.in i am getting returned as www.google.com but if i input httpasd://www.google.co.in i am getting httpasd ..there should not be any match na y i am getting the match ???

Alex Martelli · Accepted Answer · 2010-09-03 20:52:47Z

The http:// doesn't match, but then it's optional, so that's no problem; the "one or more characters that aren't slashes" matches httpasd:, and of course the .* then matches everything that follows, from the slashes (included) onwards. This would work the same way with any common regex implementation, nothing c++ specific about it!

@raj, that entirely depends on what you're trying to match, and what you're trying not to match. I'm glad @Greg was able to divine that (I infer from your acceptance), because my thought-reading abilities are limited;-).

Greg Domjan · Accepted Answer · 2010-09-03 21:02:13Z

^(?:http://)?([^\\/]+)(.*)$

the ? at the end of (?:http://)? means that bit is optional
this ([^\\/]+) captures and matches anything that is not a \ or /
this (.*) captures everything else up to the end of the line

Perhaps your after something more like ^(?:https?://)([^\\/]+)(.*)$

might like to consider full URL syntax along the lines of

 file:// /C:/temp/app/example.html file:// C : /temp/app/example.html file:// C : \temp\app\example.html http://[email protected]:8080/test/url.htm?view=smart [method][ server ][ path ][optional] [user][ domain ][port]

Then your heading for a regex more like

([a-zA-Z][a-zA-Z0-9\\+\\-\\.]*://)?(([^@/\\\\]+@)?([a-zA-Z0-9_'!~\\-,;&=\\.\\$\\*\\(\\)\\+]+)(:\\d*)?)?([/\\\\][^?]*)?(\\?.*)?

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