Question

RegEx: help fine-tune url string matching

Asked by: MichaelEvangelista

I have a CF function - gleaned, I think, from a previous ExEx response - which takes a large amount of plain text or html, and finds all of the url strings that are not already linked, beginning with "www" or "http", and creates actual hyperlinks when output to the page.

It works pretty well, but there are a few issues I am hoping to fine-tune.

1) Most important - if there is not a space after the last character of the url (i.e. ".com" is followed by a period, or, if html, by a closing </p> tag with no space), those characters get included in the match and I end up with a bad link.

2) I need this to also match "https://" links, which means altering the way it does the 'replace ' part of the function, since the http:// is currently hard coded.

Note - the 'request.smartlinknew' is my own code, using David Powers' SmartLink JS to open these links in a new window.

Thanks in advance for your help!

<cffunction name="LinkURLs" output="true" returntype="string">
 
<cfargument name="text" type="string" required="yes">
<!--- Define local variables --->
<cfset var pos=1>
<cfset var subex="">
<cfset var done=false>
<cfset results = arguments.text>
 
<cfloop condition="not done">
 
<!--- Perform search --->
<cfset subex=reFind("(http://|http://www|www)(.*?)([[:space:]]|$)", arguments.text, pos, true)>
<!--- Anything matched? --->
<cfif subex.len[1] is 0>
<cfset done=true>
<cfelse>
<cfsavecontent variable="theLink"><a href="http://#replace(mid(text,subex.pos[1],subex.len[1]),'http://','')#" #request.SmartLinkNew#>#mid(text,subex.pos[1],subex.len[1])#</a></cfsavecontent>
<cfset results = replace(results,mid(text,subex.pos[1],subex.len[1]),theLink)>
<!--- Reposition start point --->
<cfset pos=subex.pos[1]+subex.len[1]>
</cfif>
</cfloop>
 
<!--- and return results --->
<cfreturn results>
</cffunction>

                                  
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Asked On
2009-03-02 at 09:12:41ID24190629
Tags

ColdFusion

,

RegEx

,

URL

Topics

ColdFusion Application Server

,

Miscellaneous Programming

,

Scripting Languages

Participating Experts
1
Points
500
Comments
4

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Answers

 

by: steezaPosted on 2009-03-04 at 05:32:13ID: 23794510

1: Try (http://|https://|www)(.*?)(?=[^a-zA-z0-9]*([[:space:]]|($))) for your reFind expression.

2: As for your URL rendering bit, I would go for something like:
If the link starts with https or http then put it in as is, otherwise append the http://


 

by: steezaPosted on 2009-03-04 at 05:39:16ID: 23794569

In addition: http://www.bennadel.com/blog/487-Using-Verbose-Regular-Expressions-To-Explain-Url-Auto-Linking-In-ColdFusion.htm provides an interesting example around url matching regexes.

 

by: MichaelEvangelistaPosted on 2009-04-11 at 12:28:16ID: 24123159


@steeza
>> 1: Try (http://|https://|www)(.*?)(?=[^a-zA-z0-9]*([[:space:]]|($))) for your reFind expression.

This is slightly better, a period following the link is now excluded. But if the link is immediately followed by an html tag, i.e.  

www.something.com<br />

The link looks like this

 href="http://www.something.com<br">

with the first part of the html tag   " <br  " included inside the href attribute, and the rest,   " /> " , visible on the page.


 

by: MichaelEvangelistaPosted on 2009-04-11 at 12:50:28ID: 24123239

aha!

This
>> http://www.bennadel.com/blog/487-Using-Verbose-Regular-Expressions-To-Explain-Url-Auto-Linking-In-ColdFusion.htm

was actually very helpful! Ben to the rescue again!
I gleaned the proper regex from his code, and added my own option to check for https as the first 5 chars, otherwise assume http

My completed link matching function is below, hopefully others can use it as well.
Full points, thanks again!

<cffunction name="LinkURLs" output="true" returntype="string">
 
<cfargument name="text" type="string" required="yes">
<!--- Define local variables --->
<cfset var pos=1>
<cfset var subex="">
<cfset var done=false>
<cfset results = arguments.text>
 
<cfloop condition="not done">
 
<!--- Perform search --->
<!---ORIGINAL:
<cfset subex=reFind("(http://|http://www|www)(.*?)([[:space:]]|$)", arguments.text, pos, true)>  --->
<!---EX-EX:
<cfset subex=reFind("(http://|https://|www)(.*?)(?=[^a-zA-z0-9]*([[:space:]]|($)))", arguments.text, pos, true)>  --->
<!--- BEN NADEL: --->
<cfset subex=reFind("(((https?:|ftp:|gopher:)\/\/)|(www\.|ftp\.))[-[:alnum:]\?%,\.\/&##!;@:=\+~_]+[A-Za-z0-9\/]", arguments.text, pos, true)> 
<!--- Anything matched? --->
 
	<cfif subex.len[1] is 0>
<cfset done=true>
<cfelse>
 
	<cfif left(mid(text,subex.pos[1],subex.len[1]), 5) is 'https'><cfset prefix = "https://"><cfelse><cfset prefix = "http://"></cfif>
	<cfset linktext = replace(mid(text,subex.pos[1],subex.len[1]),'#prefix#','')>
<cfsavecontent variable="theLink"><a href="#prefix##linktext#" #request.SmartLinkNew#>#mid(text,subex.pos[1],subex.len[1])#</a></cfsavecontent>
<cfset results = replace(results,mid(text,subex.pos[1],subex.len[1]),theLink)>
<!--- Reposition start point --->
<cfset pos=subex.pos[1]+subex.len[1]>
</cfif>
</cfloop>
 
<!--- and return results --->
<cfreturn results>
</cffunction>

                                              
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