regex_search matching unspecified text

Question

I've been using Boost::regex and Boost::regex_search and found that when I run the regex

\\<(\\w+\\-?\\w+)\\>

These all get matched like normal

BitcoinicaHacker> Who wants free bitcoins courtesy of bitcoinica?
<grepix> who doesn't!
<BitcoinicaHacker> post your btc addr
<nanotube> i think bitcoinica wants free bitcoins courtesy of bitcoinica

But lines like this also get matched

--> peacekeep3r (~peacekeep@chello084114169104.2.15.vie.surfer.at) has joined #bitcoin
<-- Raccoon has quit (Changing host)
--> Raccoon (bismuth@unaffiliated/raccoon) has joined #bitcoin

This is rather confusing since I specifically asked it to find a left angle bracket then text that might have a dash and then a right angle bracket.

Update 2:

Thanks to Ωmega for helping me find the best solution: <(\\w+(?:\\-\\w+)*)>

Update:

Either

<(\\w+\\-?\\w+)> or <([^-<>]+[^<>]*)> works for my purposes.

I forgot to remove the escape slashes.

Could this be related to not using the starting and ending anchors? (^ and $) — BlackVegetable, Jun 28 '12 at 16:52
I just tried with that and it no longer matches anything. I tried also just the ^ at the beginning, but that didn't work either. AFAIK those have to do with beginning of the input string and ending so if I put those on it would be the same as using regex_match and I would have to supply everything else that might be in the line also. — trippedoutfish, Jun 28 '12 at 17:05

Ωmega · Accepted Answer · 2012-06-28T17:33:18.487

0

Try to use regex <([^-<>]+[^<>]*)> which reads:

Match content between < and > that starts with character other than -, <, or >, followed by any combination (also empty) of characters other than < or >.

Update:

You may also consider to use regex <((?!\\-\\-)[^<>]+)> which reads:

Match content between < and > that does not start with -- and does not contain any < or >.

edited Jun 28 '12 at 17:33

answered Jun 28 '12 at 17:08

Ωmega

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Thanks. This works! Mind explaining a bit as to why this works correctly and how it is better? – trippedoutfish Jun 28 '12 at 17:13
It makes sure the 2nd character is not `-`, which is part of `-->` and `<--`. The name on IRC can contain `-`, but I'm not sure if it can start with `-` - such user might escape the match. – nhahtdh Jun 28 '12 at 17:15
@nhahtdh - you mean something like `<-this is a tag>`? I don't think that it is allowed to start with `-`, but it is up to OP to say... But I have updated my answer with an alterntive solution. – Ωmega Jun 28 '12 at 17:19
I just checked http://www.mirc.com/rfc2812.html , and the first character cannot be `-`. The name also cannot contain `<` or `>`. – nhahtdh Jun 28 '12 at 17:23
So I just realized that I escaped my angle brackets, and without those it works perfectly as well. '<(\\w+\\-?\\w+)> ' I can't get the code formatting in my comment to work >_> – trippedoutfish Jun 28 '12 at 17:26
@trippedoutfish - your regex would not work with one character tags, such as ``, or multiple dash tags, such as ``, unless you change the inside pattern to `(\\w+(?:\\-\\w+)*)` – Ωmega Jun 28 '12 at 17:30
@Ωmega - That does seem like the most elegant answer. Thanks for all the help. – trippedoutfish Jun 28 '12 at 17:36

regex_search matching unspecified text

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