JMeter - Running preprocessor when called from command line? - bash

Question

I'm very new to JMeter.
My team has existing JMeter Test Plans that we generally run through the GUI. I am experimenting with running it from the command line.
In our test plans, we have a bunch of variables declared at the TestPlan level. These variables contain information for setting up different environments (eg test, prod, dev). Directly under the TestPlan is a JSR223 PreProcessor that basically takes the variable that shows what environment you're trying to run in and sets up the hostname, port, etc to the values for that environment.
When I run the test using the GUI, it works perfectly under the selected environment. However, when I run it with the command line using the following command:
jmeter -n -t testName.jmx -l Results.csv
it tries to run under the defaulted environment and doesn't change it to the environment I want. I tried adding a -Jenv=dev, but that didn't seem to make any difference.
Do preprocessors not run when called from the command line? Could there be something else that I'm missing? Given my inexperience here, I'm not even really sure how I can tell what the problem is.
Thanks so much!

Answer 1

It is very difficult to conclude what is the exact problem in your jmeter script. Looking into the problem statement I can sense that you need to find correct way of passing a variable from command line and processing it in a script.
Example of passing a variable from command line and handling it in jmeter is shown below:
Declare a variable with value as a property in jmeter. You can use anything here, I have used User Defined variable. Variable env is declared as ${__P(env)}
Using JSR to process that variable. Here just printing the value passed from parameter into jmeter log. Now the value can be reused using ${env} variable [note it is a variable and not a property, because we declared that way in User Defined variable].
String valuePassed = vars.get("env");
log.info("Parameter passed from command line: " + valuePassed);
Run from the Command Line using following command:
jmeter -n -t <>.jmx -Jenv=Prod -j sample.log
Result shown in log file

Answer 2

PreProcessors are executed only in conjunction with Samplers
If you don't have any Sampler in your Thread Group - none of PreProcessors will be executed.
Also be aware that PreProcessors obey JMeter Scoping Rules to wit:
if you have a PreProcessor added as a child of the Sampler - the PreProcessor will be executed before the given Sampler
if you have 2 Samplers and a PreProcessor at the same level - the PreProcessor will be executed before each Sampler