Script blocks for Groovy in Jenkins - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a Groovy script block in Jenkins pipeline.

Jenkins

pipeline {
  agent any
  stages {
    stage('Example') {
      steps {
        [1] {
          echo 'Hello from Groovy script!'
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Ash

Bgroovy

Cbat

Dscript

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'sh' or 'bat' blocks which run shell or batch commands, not Groovy code.

Trying to use 'groovy' as a block name which is not valid.

The script block allows running Groovy code inside a Jenkins pipeline.

2fill in blank

medium

Complete the code to assign a variable inside a Groovy script block.

Jenkins

pipeline {
  agent any
  stages {
    stage('Set Variable') {
      steps {
        script {
          def message = [1]
          echo message
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A"Hello, Jenkins!"

BHello, Jenkins!

C'Hello Jenkins'

DHello Jenkins

Attempts:

3 left

💡 Hint

Common Mistakes

Not using quotes causes syntax errors.

Using single quotes is valid but here double quotes are preferred.

Strings in Groovy must be quoted. Double quotes allow interpolation if needed.

3fill in blank

hard

Fix the error in the Groovy script block to correctly loop over a list.

Jenkins

pipeline {
  agent any
  stages {
    stage('Loop') {
      steps {
        script {
          def items = ['a', 'b', 'c']
          for (item [1] items) {
            echo item
          }
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

Ain

Bof

C=

Dto

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'of' or '=' causes syntax errors.

Using 'to' is incorrect for looping over collections.

Groovy uses in to loop over collections in for loops.

4fill in blank

hard

Fill both blanks to create a Groovy map with keys and values inside a script block.

Jenkins

pipeline {
  agent any
  stages {
    stage('Map') {
      steps {
        script {
          def data = [[1]: 'apple', [2]: 'banana']
          echo data['fruit1']
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

A'fruit1'

B'fruit2'

Cfruit1

Dfruit2

Attempts:

3 left

💡 Hint

Common Mistakes

Using unquoted keys causes errors or treats keys as variables.

Mixing quoted and unquoted keys inconsistently.

Map keys as strings must be quoted. Here keys are 'fruit1' and 'fruit2'.

5fill in blank

hard

Fill all three blanks to filter a list inside a Groovy script block using a closure.

Jenkins

pipeline {
  agent any
  stages {
    stage('Filter') {
      steps {
        script {
          def numbers = [1, 2, 3, 4, 5]
          def evens = numbers.findAll { [1] -> [2] [3] 2 == 0 }
          echo evens.toString()
        }
      }
    }
  }
}

Drag options to blanks, or click blank then click option'

An

C%

D==

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for parameter and variable causes errors.

Using '==' instead of '%' for modulo causes wrong filtering.

The closure uses n -> n % 2 == 0 to find even numbers.

Practice

1. What is the main purpose of using script blocks in Jenkins pipelines?

easy

A. To define environment variables

B. To specify the agent where the pipeline runs

C. To run Groovy code for custom logic inside the pipeline

D. To declare pipeline stages

Solution

1. Step 1: Understand Jenkins pipeline structure

   Jenkins pipelines use declarative syntax but allow Groovy code inside script blocks for flexibility.

2. Step 2: Identify the role of script blocks

   script blocks let you write Groovy code for loops, conditions, and other logic not directly supported in declarative syntax.

3. Final Answer:

   To run Groovy code for custom logic inside the pipeline -> Option C

4. Quick Check:

   Script blocks = Groovy code inside pipeline [OK]

Hint: Script blocks run Groovy code inside steps [OK]

Common Mistakes:

• Confusing script blocks with environment or agent declarations
• Thinking script blocks define stages
• Assuming script blocks are optional for all logic

2. Which of the following is the correct way to start a script block inside a declarative Jenkins pipeline?

easy

A. script { echo 'Hello' }

B. script: { echo 'Hello' }

C. script() { echo 'Hello' }

D. script => { echo 'Hello' }

Solution

1. Step 1: Recall correct syntax for script blocks

   In declarative pipelines, script is a block keyword followed by curly braces containing Groovy code.

2. Step 2: Compare options

   Only script { ... } is valid Groovy block syntax. Others use invalid punctuation or keywords.

3. Final Answer:

   script { echo 'Hello' } -> Option A

4. Quick Check:

   script block syntax = script { ... } [OK]

Hint: Use script { } with braces, no colons or arrows [OK]

Common Mistakes:

• Using colons or arrows instead of braces
• Adding parentheses after script keyword
• Misplacing quotes or braces

3. What will be the output of this Jenkins pipeline snippet?

pipeline {
  agent any
  stages {
    stage('Example') {
      steps {
        script {
          def sum = 0
          for (i in 1..3) {
            sum += i
          }
          echo "Sum is ${sum}"
        }
      }
    }
  }
}

medium

A. Sum is 6

B. Sum is 3

C. Sum is 0

D. Syntax error

Solution

1. Step 1: Analyze the for loop inside script block

   The loop runs from 1 to 3 inclusive, adding each number to sum: 1 + 2 + 3 = 6.

2. Step 2: Understand echo output

   The echo prints the string with sum value interpolated, so output is "Sum is 6".

3. Final Answer:

   Sum is 6 -> Option A

4. Quick Check:

   1+2+3=6 output = Sum is 6 [OK]

Hint: Sum 1 to 3 = 6; echo prints it [OK]

Common Mistakes:

• Thinking loop ends at 2
• Confusing sum initialization
• Assuming syntax error due to script block

4. Identify the error in this Jenkins pipeline snippet using a script block:

pipeline {
  agent any
  stages {
    stage('Test') {
      steps {
        script {
          for i in 1..3 {
            echo "Number: ${i}"
          }
        }
      }
    }
  }
}

medium

A. Script block must be outside steps

B. Incorrect use of echo inside script block

C. Agent declaration is invalid

D. Missing parentheses around for loop variable and range

Solution

1. Step 1: Check for loop syntax in Groovy

   Groovy requires parentheses around the for loop variable and range: for (i in 1..3).

2. Step 2: Identify the error in given code

   The code uses for i in 1..3 without parentheses, causing syntax error.

3. Final Answer:

   Missing parentheses around for loop variable and range -> Option D

4. Quick Check:

   Groovy for loop needs ( ) [OK]

Hint: Always use parentheses in Groovy for loops [OK]

Common Mistakes:

• Omitting parentheses in for loops
• Misplacing script block outside steps
• Confusing echo usage inside script

5. You want to use a script block in Jenkins to create a map of numbers to their squares for numbers 1 to 4, then print each pair. Which code snippet correctly does this inside a script block?

hard

A. def squares = []
for (i in 1..4) {
squares.add(i * i)
}
squares.each { echo "${it} squared" }

B. def squares = [:]
for (i in 1..4) {
squares[i] = i * i
}
squares.each { k, v -> echo "${k} squared is ${v}" }

C. def squares = [:]
for i in 1..4 {
squares[i] = i * i
}
squares.each { k, v -> echo "${k} squared is ${v}" }

D. def squares = [:]
for (i in 1..4) {
squares[i] = i ^ 2
}
squares.each { k, v -> echo "${k} squared is ${v}" }

Solution

1. Step 1: Check map creation and loop syntax

   def squares = [:] for (i in 1..4) { squares[i] = i * i } squares.each { k, v -> echo "${k} squared is ${v}" } correctly creates an empty map with [:] and uses parentheses in the for loop.

2. Step 2: Verify square calculation and iteration

   def squares = [:] for (i in 1..4) { squares[i] = i * i } squares.each { k, v -> echo "${k} squared is ${v}" } uses i * i for squares and iterates map with each { k, v -> ... } to echo key-value pairs.

3. Final Answer:

   def squares = [:] for (i in 1..4) { squares[i] = i * i } squares.each { k, v -> echo "${k} squared is ${v}" } -> Option B

4. Quick Check:

   Map with for (i in 1..4) and i*i is correct [OK]

Hint: Use [:] for map, for (i in range), i*i for squares [OK]

Common Mistakes:

• Using list [] instead of map [:]
• Omitting parentheses in for loop
• Using ^ for power instead of *
• Incorrect map iteration syntax