Jenkins Environments

To see all jenkins pre-defined variables, https://ip-address:8080/env-vars.thml
To print all environment variables
```
sh "printenv | sort"
```

Using env variables

// ${env.BUILD_NUMBER} or ${BUILD_NUMBER} are same
echo "BUILD_NUMBER = ${env.BUILD_NUMBER}"
// If you are sh block you access variable directly like this $BUILD_NUMBER
sh 'echo BUILD_NUMBER = $BUILD_NUMBER'

Setting env variables. All the environment variables are casted to string

Environment in pipeline block (Accessible to all stages)

pipeline {
  agent any
  environment {
      USER_NAME = "vignesh"
      USER_ID = 23 // All the environment variable are casted to string
  }
}

Environments at stage level (only accessible to that stage)

stage ("Using environment variable") {
  environment {
      USER_PATH = "/home/vignesh"
  }
  steps {
      echo "USER_PATH = ${env.USER_PATH}"
  }
}

Using script block inside the stage

stage ("Using environment variable") {
  steps {
      script {
          env.USER_GROUP = "users"
      }
      echo "USER_GROUP = ${env.USER_GROUP}"
  }
}

Using withEnv inside the stage

stage ("Using environment variable") {
  withEnv(["USER_PSD=secret", "USER_ID_ADMIN=false"]) {
      echo "USER_PSD = ${USER_PSD}"
      sh 'USER_ID_ADMIN = $USER_ID_ADMIN'
  }
}

Overriding env variables

we can override the environments in pipeline environment block with the environments defined in stage environment block

pipeline {
    agent any
    environment {
        USER_NAME = "vignesh"
        USER_ID = 23 // All the environment variable are casted to string
    }
    stage ("Using environment variable") {
        environment {
            USER_NAME = "venkatesh"
        }
        steps {
            echo "USER_NAME = ${env.USER_NAME}" //Now the USER_NAME value is venkatesh only in this stage, outside the stage the value will be from pipeline                   environment block
        }
    }
    stage ("Accessing environment variables") {
        steps {
            sh 'echo USER_NAME = $USER_NAME' // Here the value is 'vignesh' from pipeline environment block
        }
    }
}

Overriding the value in script block will not have any effect

pipeline {
    agent any
    environment {
        USER_NAME = "vignesh"
        USER_ID = 23 // All the environment variable are casted to string
    }
    stage ("Overriding in script block") {
        steps {
            script {
                env.USER_NAME = "vijay"  // will not have any effect
            }
            echo "USER_NAME = ${env.USER_NAME}"
        }
    }
}

Overriding the value in withEnv block

pipeline {
    agent any
    environment {
        USER_NAME = "vignesh"
        USER_ID = 23 // All the environment variable are casted to string
    }
    stage ("Overriding with withEnv block") {
        steps {
            withEnv(["USER_NAME=Panda"]) {
                echo "USER_NAME = ${env.USER_NAME}" // will print Panda
            }
            echo "USER_NAME = ${env.USER_NAME}" // will print value "vignesh" from pipeline environment block
        }
    }
}

Using env vaibale as boolean

The env varibale is actually a string, so it wont work or we have to check like this (env.TRIGGER_NEXT == “true”), “true” as string

stage ("Using env vaibale as boolean (not working)") {
    when {
        expression {
            // Here the env.TRIGGER_NEXT is actually "true" (string) so the condition is false
            env.TRIGGER_NEXT == true
        }
    }
    steps {
        echo "OK"
    }
}

Converting string to Boolean value (not the suggested way)

stage ("Converting string to boolean") {
    when {
        expression {
            env.TRIGGER_NEXT.toBoolean() == true
        }
    }
    steps {
        echo "OK"
    }
}

Using environment as condition

stage ("Using environment as condition") {
    environment {
        TRIGGER_NEXT = "true" // true as string in double quotes
    }
    when {
        expression {
            environment name: "TRIGGER_NEXT", value: "true"
        }
    }
    steps {
        echo "OK"
    }
}

Storing scrit output to environment variable

using sh step block simply

stage ("Storing sh step output to environment variable") {
    environment {
        // sh step by default will not return any value
        FILES_COUNT = sh "ls -al /tmp | wc -l" 
    }
    steps {
        echo "The tmp folder has ${FILES_COUNT} files"
    }
}

using sh step block with parameters

stage ("Storing sh step with parameters output to environment variable") {
    environment {
        // we have to trim the output otherwise we will have some whitespace
        FILES_COUNT = sh (script: "ls -al /tmp | wc -l", returnStdout: true).trim()
    }
    steps {
        echo "The tmp folder has ${FILES_COUNT} files"
    }
}