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Classic ASP Extract Substring between 2 points

Posted on 2011-03-17
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Last Modified: 2012-05-11
Hi,

This is my text string in ASP:
http://www.google.es/#hl=es&xhr=t&q=glass+curtains&cp=4&pf=p&sclient=psy&site=&source=hp&aq=0&aqi=&aql=&oq=glass+&pbx=1&fp=7a027991ed21ee0a

The string can change but defining start is "&q=" and end is the next "&"

I need to put the part between that into a substring - in this case it would be "glass+curtains"

Thanks,

Ben
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Question by:intangiblemedia
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10 Comments
 
LVL 52

Assisted Solution

by:Carl Tawn
Carl Tawn earned 800 total points
ID: 35155166
Try this:
<%
   url = "http://www.google.es/#hl=es&xhr=t&q=glass+curtains&cp=4&pf=p&sclient=psy&site=&source=hp&aq=0&aqi=&aql=&oq=glass+&pbx=1&fp=7a027991ed21ee0a"
   
   startPos = InStr(url, "q=") + 2
   endPos = InStr(startPos+1, url, "&")

   Response.Write "Start: " & startPos & "<br />"
   Response.Write "End: " & endPos & "<br />"

   If endPos < 0 Then
      endPos = Len(url)
   End If

   query = Mid(url, startPos, endPos - startPos)
   Response.Write query
%>

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0
 

Author Comment

by:intangiblemedia
ID: 35155343
Thanks, that is nearly working now!!

Just one issue:
Microsoft VBScript runtime error '800a0005'

Invalid procedure call or argument: 'Mid'

/includes/seo.inc, line 16

this happened when I changed the code see line 2 from a static string to actually request HTTP Server Variables... I think I need to put "" around it, but I cant work it out.... Please help many thanks
<%
   url = Request.ServerVariables("HTTP_REFERER")
   
   startPos = InStr(url, "q=") + 2
   endPos = InStr(startPos+1, url, "&")

   Response.Write "Start: " & startPos & "<br />"
   Response.Write "End: " & endPos & "<br />"

   If endPos < 0 Then
      endPos = Len(url)
   End If

   query = Mid(url, startPos, endPos - startPos)
   Response.Write query
%>

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0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 35155367
You shouldn't do. Add:
Response.Write url

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Immediately after the line:
url = Request.ServerVariables("HTTP_REFERER")

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To verify what value it is actually pulling back.
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Author Comment

by:intangiblemedia
ID: 35155449
Its kind of hard because i dont have the test asp page indexed in the search engine if that makes sense...

All I know, I have done various tests:
url = "http://www.google.es/#hl=es&xhr=t&q=cortinas+de+cristal&cp=0&pf=p&sclient=psy&site=&source=hp&aq=0&aqi=&aql=&oq=cortinas+d&pbx=1&fp=7a027991ed21ee0a"

url = "http://www.google.es/#sclient=psy&hl=es&q=glass+curtains&aq=f&aqi=&aql=&oq=&pbx=1&fp=7a027991ed21ee0a"

all work fine if its a static string enclosed with commas... but as soon as I do it live
      

url = Request.ServerVariables("HTTP_REFERER")

it doesnt work...

What do you suggest?
0
 
LVL 52

Expert Comment

by:Carl Tawn
ID: 35155478
I would guess that HTTP_REFERER isn't pulling back the value that you are expecting it to. Or possibly that the "q" parameter is the last one in the query string. Try changing the code to the following and seeing what happens:

As a sanity check try using:
<%
   url = Request.ServerVariables("HTTP_REFERER")
   
   startPos = InStr(url, "q=") + 2
   If startPos > 0 Then

       endPos = InStr(startPos+1, url, "&")

       Response.Write "Start: " & startPos & "<br />"
       Response.Write "End: " & endPos & "<br />"

       If endPos = 0 Then
          endPos = Len(url)
       End If

       query = Mid(url, startPos, endPos - startPos)
       Response.Write query
    Else
        Response.Write "query parameter not found"
    End If
%>

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0
 
LVL 18

Expert Comment

by:mgfranz
ID: 35158375
Why not use a RegExp?  It's cleaner and simpler.
<%
url = Request.ServerVariables("HTTP_REFERER")
   
Dim myRegExp
Set myRegExp = New RegExp
myRegExp.IgnoreCase = True
myRegExp.Global = True
myRegExp.Pattern = "&q=(.*?)&"
Set myMatches = myRegExp.Execute(url)

If myMatches.Count >= 1 Then ' Successful match
	For Each myMatch In myMatches
		For I = 1 To myMatch.SubMatches.Count
			resultStr = myMatch.SubMatches(I-1) ' Return the group result
			Response.Write "Match found and contains " & resultStr 
		Next
	Next	
Else
	Response.Write "No Match Found" ' Match attempt failed
End If
%>

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0
 
LVL 6

Expert Comment

by:worthyking1
ID: 35209454
Here you go. This will work every time.
<%
RefURL = Request.ServerVariables("HTTP_REFERER")
sPos = InStr(RefURL, "q=") + 2
ePos = InStr(sPos+1, RefURL, "&")
If ePos = 0 Then ePos = Len(RefURL)   
query = Mid(RefURL, sPos, ePos - sPos)
Response.Write query
%>

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0
 
LVL 6

Accepted Solution

by:
worthyking1 earned 1200 total points
ID: 35209486
Actually, let's alter that to account for a page visit that does NOT come from Google (otherwise it would generate an error if it could not find the "q=" starting point).
<%
RefURL = Request.ServerVariables("HTTP_REFERER")
sPos = InStr(RefURL, "q=") + 2
If sPos > 2 then
	ePos = InStr(sPos+1, RefURL, "&")
	If ePos = 0 Then ePos = Len(RefURL)   
	query = Mid(RefURL, sPos, ePos - sPos)
End if
Response.Write query
%>

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0
 
LVL 18

Expert Comment

by:mgfranz
ID: 35209623
Use the Regex I suggested, it's more forgiving.  If there is no "q=" in the refer string it will exit gracefully.
0
 

Author Closing Comment

by:intangiblemedia
ID: 35216463
Thank you all - Splitting points as I nearly had a complete solution but worthyking1 gave me what I needed in the end.
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