Using sed in Jenkins Groovy pipeline

I spent some time trying to figure out how to fix unexpected slash char error in my pipeline.

My aim was to change some value in a config file after checking out a Git repository. I have a Jenkins pipeline and I used sed to perform the substitution.

The pipeline wouldn't even compile because of Groovy's way of handling slashes. I was constantly getting "unexpected slash char" error.

Eventually, I made it work this way:

stage('Some stage') {
    steps {
        sh script: $/
            sed -i 's/^\(SOME_VAR=*\).*$/\1SOME_VAL/' ./config/default.conf
        /$
    }
}

Having the following default.conf:

SOME_VAR=Literally any string value

The pipeline's step will turn it into:

SOME_VAR=SOME_VAL

Good job, I think :-)