Loading libraries in Jenkinsfile - Step-by-Step Execution

Process Flow - Loading libraries in Jenkinsfile

Start Jenkinsfile Execution

↓

Load Shared Library

↓

Library Methods Available

↓

Call Library Functions

↓

Continue Pipeline Steps

↓

End

The Jenkinsfile starts, loads a shared library, makes its functions available, calls them, then continues the pipeline.

Execution Sample

Jenkins

@Library('my-shared-lib') _

pipeline {
  agent any
  stages {
    stage('Use Lib') {
      steps {
        script {
          myFunction()
        }
      }
    }
  }
}

This Jenkinsfile loads a shared library named 'my-shared-lib' and calls a function 'myFunction' from it during the pipeline.

Process Table

Step	Action	Evaluation	Result
1	Start Jenkinsfile	N/A	Jenkinsfile execution begins
2	Load library 'my-shared-lib'	@Library('my-shared-lib') _	Library loaded, functions available
3	Enter pipeline stage 'Use Lib'	stage('Use Lib')	Stage starts
4	Call function 'myFunction()' from library	myFunction()	Function executes successfully
5	Complete stage 'Use Lib'	stage complete	Stage ends
6	Pipeline ends	pipeline complete	Pipeline execution finishes

💡 Pipeline completes after all stages and library functions run

Status Tracker

Variable	Start	After Step 2	After Step 4	Final
libraryLoaded	false	true	true	true
myFunctionCalled	false	false	true	true

Key Moments - 2 Insights

Why do we need to load the library before calling its functions?

Because the library functions are not available until Jenkins loads the library (see execution_table step 2). Calling functions before loading causes errors.

What happens if the library name is wrong?

Jenkins will fail at the library loading step (step 2) and stop the pipeline, because it cannot find the library.

Visual Quiz - 3 Questions

Look at the execution table, at which step is the library loaded?

A Step 1

B Step 4

C Step 2

D Step 6

💡 Hint

Check the 'Action' column for 'Load library' in execution_table row 2

According to variable_tracker, when does 'myFunctionCalled' become true?

A After Step 4

B After Step 2

C At Start

D Never

💡 Hint

Look at 'myFunctionCalled' row in variable_tracker after Step 4

If the library was not loaded, what would happen when calling 'myFunction()'?

A Function runs normally

B Pipeline fails with error

C Pipeline skips the function

D Function runs but returns null

💡 Hint

Refer to key_moments about calling functions before loading library

Concept Snapshot

Loading libraries in Jenkinsfile:
- Use library 'name' to load shared libraries
- Load before calling any library functions
- Loaded functions become available in pipeline
- Calling functions before loading causes errors
- Libraries help reuse code across pipelines

Full Transcript

This visual execution shows how Jenkinsfile loads a shared library named 'my-shared-lib'. The pipeline starts, then Jenkins loads the library making its functions available. Next, the pipeline enters a stage where it calls a function 'myFunction' from the library. After the function runs, the stage and pipeline complete. Variables track that the library is loaded before the function call. Key moments explain why loading first is important and what happens if the library name is wrong. The quiz tests understanding of when loading happens and effects of missing library load.