How can I get the last match in regular extracor expression in jmeter?

Question

I would like to extract the last occurence of regular expression in Jmeter. I used Regular Extractor expression to do this, but I can't got the last occurence.

I tried this :

• Regular expression: "var1":([^"]+),"var2"
• Template : $1$
• Match No : -1
• Default value : expression_matchNr

Then in my script I used ${expression} variable

I've tested expression_matchNr but it give me the number of match.

What should I put in "Match No:" ?

Thanks in advance

Answer 1

If you have the following output:

expression=foo
expression_1=foo    
expression_2=bar
expression_3=**what you looking for**
expression_matchNr=3

You can use JMeter's __V function to get value of expression_3 variable

As per function's description:

For example, if one has variables A1,A2 and N=1:

• ${A1} - works OK
• ${A${N}} - does not work (nested variable reference)
• ${__V(A${N})} - works OK. A${N} becomes A1, and the __V function returns the value of A1

So in your case the function, returning last match no matter how many matches are will look like:

${__V(expression_${expression_matchNr})}

See How to Use JMeter Functions post series on what else can be done with functions.

Answer 2

Unfortunately the JMeter core does not support the -1,-2... for ultimate/penultimate etc. notation. You can however find the ultimate occurrence using a negative look-ahead

I stumbled on this problem and for me I solved it using something like this:

[\s\S]*("var1":([^\"]+),"var2")(?!$1$)

and Template: $2$

explanation: match anything until (..1..)-happens where it is not possible to match (..1..) after. Return (..2..)

Also the first occurrence of the item:

 ("var1":([^\"]+),"var2")(?!$1$)[\s\S]*

As for efficiency, this saves the entire query [\s\S]* in a variable, so it is a bit heavy and I haven't tested if it pulls too much memory If it does, consider using javaScript or JQuery which does support last object methods