05-groovy-shared-library.txt

Documantation: https://jenkins.io/doc/book/pipeline/shared-libraries/
Example: https://github.com/monodot/pipeline-library-demo

1. create a directory called vars under specific GIT repo.
This will hold your custom steps. 
Each of them will be a different .groovy file underneath your vars directory, e.g.:

vars/
    deployApplication.groovy
    parseFile.groovy
    sayHello.groovy
    readSystemCredentials.groovy
    doCodeReview.groovy

Each of your custom steps is a different .groovy file inside your vars/ directory. 
In Jenkins terminology, these are called Global Variables, which is why they are located inside vars/


2. Add a custom step
Create a file for your custom step, and fill in the code. For example, a simple greeting function would look like this:

#!/usr/bin/env groovy

def call(String name = 'human') {
  echo "Hello, ${name}."
}


3. Set up the library in Jenkins

In Jenkins, go to Manage Jenkins → Configure System. Under Global Pipeline Libraries
add a library with the following settings:

Name: pipeline-library-demo
Default version: Specify a Git reference (branch or commit SHA), e.g. master
Retrieval method: Modern SCM
Select the Git type
Project repository: https://github.com/monodot/pipeline-library-demo.git

4. Use the library in a pipeline
To use the shared library in a pipeline, you just add @Library('your-library-name') to the top of your pipeline definition, or Jenkinsfile. Then call your step by name, e.g. sayHello

@Library('pipeline-library-demo')_

stage('Demo') {
    echo 'Hello world'
    sayHello 'Dave'
}

NOTE: The underscore (_) is not a typo! You need this underscore if the line immediately after the @Library annotation is not an import statement.