Classic ASP Extract Substring between 2 points

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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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.

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?

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

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