Joining environment variables in Jenkins pipeline / groovy

Question

I'm trying to set a couple of environment variables in a Jenkinsfile, but my lack of Java/Groovy-ness seems to be failing me...

pipeline {
    agent any
    environment {
        TMPDIR = /mnt/storage/build
        TOX_DIR = $TMPDIR/$BUILD_TAG
    }
...

Generates the following error on the console...

WorkflowScript: 7: Environment variable values can only be joined together with +s. @ line 7, column 26.
       TOX_DIR = $TMPDIR/$BUILD_TAG

Other variations such as ...

TOX_DIR = "$TMPDIR" + "/" + "$BUILD_TAG"

or

TOX_DIR = "$TMPDIR/$BUILD_TAG"

or

TOX_DIR = "${TMPDIR}/${BUILD_TAG}"

only make matters worse.

What am I missng? Thanks....

Answer 1

Using Jenkins v2.89.2 - Instead of using single quotes, double quotes worked for me.

environment{
    MESSAGE = "release-staging-${BUILD_TIMESTAMP}"
}