How to transfer a variable between jobs in a CI/CD…

Variables are usually transferred between jobs in a CI/CD process using artifacts or environment variables. Let's consider typical methods:

Artifacts: The previous job saves the variable value in a file, which is declared as an artifact. The next job downloads this artifact and reads the value from the file. Suitable for large data volumes or files.

# .gitlab-ci.yml (example for Gitlab CI)
job_producer:
  stage: build
  script:
    - echo "MY_VARIABLE_VALUE" > variable.txt
  artifacts:
    paths:
      - variable.txt

job_consumer:
  stage: deploy
  dependencies:
    - job_producer
  script:
    - MY_VARIABLE=$(cat variable.txt)
    - echo "Variable value is: $MY_VARIABLE"

Environment variables: Some CI/CD systems allow setting environment variables for subsequent jobs directly from the current job's script.

Gitlab CI: Use artifacts:reports:dotenv.

# .gitlab-ci.yml (example with dotenv)
job_producer:
  stage: build
  script:
    - echo "MY_VARIABLE=MY_VARIABLE_VALUE" > variables.env
  artifacts:
    reports:
      dotenv: variables.env

job_consumer:
  stage: deploy
  needs:
    - job: job_producer
      artifacts: true # Ensure artifacts are uploaded
  script:
    - echo "Variable value is: $MY_VARIABLE" # Variable is available directly

Jenkins Pipeline: Use stash and unstash functions for files or env for environment variables.

// Jenkinsfile (example with env)
pipeline {
    agent any
    stages {
        stage('Producer') {
            steps {
                script {
                    env.MY_VARIABLE = "MY_VARIABLE_VALUE"
                }
                echo "Set MY_VARIABLE in producer: ${env.MY_VARIABLE}"
            }
        }
        stage('Consumer') {
            steps {
                echo "Value in consumer: ${env.MY_VARIABLE}" // Variable is available
            }
        }
    }
}

or with stash/unstash:

// Jenkinsfile (example with stash/unstash)
pipeline {
    agent any
    stages {
        stage('Producer') {
            steps {
                sh 'echo "MY_VARIABLE_VALUE" > variable.txt'
                stash name: 'variable_file', includes: 'variable.txt'
            }
        }
        stage('Consumer') {
            steps {
                unstash 'variable_file'
                script {
                   def myVariable = readFile 'variable.txt'
                   echo "Value in consumer: ${myVariable}"
                }
            }
        }
    }
}

CI/CD-specific APIs: Some platforms provide APIs for saving and retrieving variables. This is a less common method for standard cases.
Shared volume: When jobs run on the same host or cluster, a shared volume can be used for temporary data storage.

The choice of method depends on the CI/CD platform used, as well as the type and volume of data being transferred. Artifacts and environment variables via platform-specific mechanisms (dotenv, set +e) are the most common and reliable approaches.

How to transfer a variable between jobs in a CI/CD process?