Pipeline utility functions in Jenkins - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of pipeline utility functions in Jenkins?

Pipeline utility functions help automate common tasks like reading files, writing files, and parsing data within Jenkins pipelines, making scripts simpler and more reusable.

beginner

How do you read a JSON file in a Jenkins pipeline using pipeline utility functions?

Use the readJSON function to read and parse a JSON file into a Groovy object for easy access to its data.

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Which pipeline utility function would you use to write a map or list to a JSON file?

Use writeJSON to convert a Groovy map or list into JSON format and save it to a file.

beginner

What does the readYaml function do in Jenkins pipelines?

readYaml reads a YAML file and converts it into a Groovy object, allowing easy access to YAML data in the pipeline.

beginner

Why are pipeline utility functions important for Jenkins pipeline scripts?

They reduce the need for complex scripting by providing ready-made functions for common tasks, improving readability and maintainability of pipeline code.

Which function reads a JSON file in a Jenkins pipeline?

A readYaml

B writeJSON

C readJSON

D writeYaml

The readJSON function reads and parses JSON files in Jenkins pipelines.

What does the writeJSON function do?

A Reads a JSON file

B Writes data to a JSON file

C Reads a YAML file

D Deletes a JSON file

writeJSON converts data to JSON format and writes it to a file.

Which pipeline utility function helps parse YAML files?

A readYaml

B readJSON

C writeJSON

D writeYaml

readYaml reads YAML files and converts them into Groovy objects.

Why use pipeline utility functions in Jenkins?

A To automate common tasks easily

B To slow down the pipeline

C To write complex shell scripts

D To avoid using Groovy

Pipeline utility functions simplify and automate common tasks in Jenkins pipelines.

Which of these is NOT a pipeline utility function?

A readJSON

B writeJSON

C readYaml

D compileCode

compileCode is not a pipeline utility function; it is unrelated to file parsing or writing.

Explain how pipeline utility functions improve Jenkins pipeline scripts.

Think about how helpers make your work easier and code cleaner.

Describe how to read and write JSON files in Jenkins pipelines using pipeline utility functions.

Focus on the two main functions for JSON handling.

Practice

1. What is the main purpose of Jenkins pipeline utility functions?

easy

A. To manage Jenkins user permissions

B. To create new Jenkins jobs automatically

C. To simplify file and data handling within Jenkins pipelines

D. To monitor Jenkins server performance

Solution

1. Step 1: Understand the role of pipeline utility functions

   These functions help with tasks like reading files, writing files, and handling data formats inside pipelines.

2. Step 2: Compare options with the main purpose

   Only To simplify file and data handling within Jenkins pipelines describes simplifying file and data handling, which matches the purpose of these functions.

3. Final Answer:

   To simplify file and data handling within Jenkins pipelines -> Option C

4. Quick Check:

   Pipeline utility functions = simplify file/data handling [OK]

Hint: Focus on file and data tasks in pipelines [OK]

Common Mistakes:

• Confusing pipeline utilities with job creation
• Thinking they manage user permissions
• Assuming they monitor server performance

2. Which of the following is the correct syntax to read a JSON file using Jenkins pipeline utility functions?

easy

A. def data = readJSON file: 'config.json'

B. def data = readJson('config.json')

C. def data = read_json file: 'config.json'

D. def data = readJSON('config.json')

Solution

1. Step 1: Recall the correct function name and syntax

   The Jenkins pipeline utility function to read JSON is readJSON with a named parameter file.

2. Step 2: Match the syntax with options

   def data = readJSON file: 'config.json' uses readJSON file: 'config.json', which is the correct syntax. Others use incorrect function names or parameter styles.

3. Final Answer:

   def data = readJSON file: 'config.json' -> Option A

4. Quick Check:

   Correct syntax = readJSON file: 'filename' [OK]

Hint: Use exact function name and named parameter 'file' [OK]

Common Mistakes:

• Using wrong function name casing
• Passing filename as positional argument
• Using underscores in function names

3. Given the following Jenkins pipeline snippet:

def content = readFile 'example.txt'
writeFile file: 'copy.txt', text: content

What will be the result after running this pipeline?

medium

A. The file 'copy.txt' will contain the same content as 'example.txt'

B. The file 'example.txt' will be deleted

C. An error occurs because writeFile requires a closure

D. The file 'copy.txt' will be empty

Solution

1. Step 1: Understand readFile usage

   The readFile function reads the entire content of 'example.txt' into the variable content.

2. Step 2: Understand writeFile usage

   The writeFile function writes the text stored in content into a new file named 'copy.txt'.

3. Final Answer:

   The file 'copy.txt' will contain the same content as 'example.txt' -> Option A

4. Quick Check:

   readFile + writeFile = copy content [OK]

Hint: readFile reads, writeFile writes content to file [OK]

Common Mistakes:

• Assuming writeFile deletes files
• Thinking writeFile needs a closure
• Expecting writeFile to append by default

4. You have this Jenkins pipeline code:

unzip zipFile: 'archive.zip', dir: 'output'

The pipeline fails with an error. What is the most likely cause?

medium

A. The 'unzip' function requires the 'zipFile' parameter to be a File object, not a string

B. The 'unzip' function is not available without the Pipeline Utility Steps plugin installed

C. The 'dir' parameter must be an absolute path, not a relative one

D. The 'unzip' function requires a closure to specify files to extract

Solution

1. Step 1: Check plugin requirement for 'unzip'

   The unzip function is part of the Pipeline Utility Steps plugin, which must be installed for it to work.

2. Step 2: Analyze error cause

   If the plugin is missing, the function call will fail regardless of parameters. Other options are incorrect because strings are accepted and relative paths work.

3. Final Answer:

   The 'unzip' function is not available without the Pipeline Utility Steps plugin installed -> Option B

4. Quick Check:

   Missing plugin = unzip fails [OK]

Hint: Check if Pipeline Utility Steps plugin is installed [OK]

Common Mistakes:

• Assuming parameter types are wrong
• Thinking relative paths are invalid
• Expecting unzip to need a closure

5. You want to check if a file named 'config.yaml' exists in your workspace before reading it in a Jenkins pipeline. Which pipeline utility function and approach should you use?

hard

A. Use readJSON file: 'config.yaml' to check and read the file

B. Use readFile('config.yaml') directly and catch exceptions if file missing

C. Use writeFile file: 'config.yaml' to create the file before reading

D. Use fileExists('config.yaml') to check existence, then readFile('config.yaml') to read

Solution

1. Step 1: Identify function to check file existence

   The fileExists function returns true if the file is present, false otherwise.

2. Step 2: Use conditional logic to read file safely

   Check with fileExists first, then read with readFile only if the file exists to avoid errors.

3. Final Answer:

   Use fileExists('config.yaml') to check existence, then readFile('config.yaml') to read -> Option D

4. Quick Check:

   Check fileExists before readFile [OK]

Hint: Always check fileExists before reading files [OK]

Common Mistakes:

• Trying to read file without checking existence
• Using readJSON on a YAML file
• Creating file before reading unnecessarily