Parameterized builds in Jenkins - Step-by-Step Execution

Process Flow - Parameterized builds

Start Build

↓

Prompt for Parameters

↓

User Inputs Values

↓

Build Uses Parameters

↓

Build Executes with Inputs

↓

Build Completes with Results

The build starts by asking for input parameters, then uses those inputs during the build execution, and finally completes with results based on those inputs.

Execution Sample

Jenkins

pipeline {
  agent any
  parameters {
    string(name: 'GREETING', defaultValue: 'Hello', description: 'Greeting message')
  }
  stages {
    stage('Say Hello') {
      steps {
        echo "${params.GREETING}, Jenkins!"
      }
    }
  }
}

This Jenkins pipeline asks for a greeting message and then prints it during the build.

Process Table

Step	Action	Parameter Value	Build Output
1	Build starts and prompts for GREETING	No value yet	Waiting for input
2	User inputs GREETING='Hi there'	Hi there	Ready to run build
3	Build runs stage 'Say Hello'	Hi there	Prints: Hi there, Jenkins!
4	Build completes	Hi there	Build success

💡 Build finishes after using the parameter value in the echo step

Status Tracker

Variable	Start	After Step 2	After Step 3	Final
params.GREETING	undefined	Hi there	Hi there	Hi there

Key Moments - 2 Insights

Why does the build ask for GREETING before running?

Because the parameter is defined in the 'parameters' block, Jenkins pauses to get user input before executing the build steps, as shown in execution_table step 1 and 2.

What happens if no input is given for GREETING?

The build uses the default value 'Hello' defined in the parameter, so the output would be 'Hello, Jenkins!' instead of a user input, as implied by the defaultValue in the code.

Visual Quiz - 3 Questions

Look at the execution table, what is the parameter value at step 3?

A "Hello"

B undefined

C "Hi there"

D null

💡 Hint

Check the 'Parameter Value' column at step 3 in the execution_table

At which step does the build print the greeting message?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the 'Build Output' column to find when the message is printed

If the user inputs no value, what will the build output be?

A "Hello, Jenkins!"

B "Hi there, Jenkins!"

C ", Jenkins!"

D Build fails

💡 Hint

Refer to the defaultValue in the parameters block in the execution_sample code

Concept Snapshot

Jenkins Parameterized Builds:
- Define parameters in 'parameters' block
- Jenkins prompts user before build starts
- Use parameters via 'params.PARAM_NAME'
- Default values used if no input given
- Enables flexible, reusable builds

Full Transcript

Parameterized builds in Jenkins let you ask users for input before running a build. You define parameters in the pipeline code, like a string parameter named GREETING with a default value. When the build starts, Jenkins pauses and asks for the GREETING value. The user types a message, for example 'Hi there'. The build then uses this input in its steps, printing the greeting message. If the user does not provide input, the default value is used. This makes builds flexible and customizable without changing code.