How to append a text to a file in jenkinsfile

Question

How to append a text to a file in Jenkinsfile injecting Jenkins BUILD_ID

I wish to see

version := \"1.0.25\"

Answer 1

The pipeline built in writeFile is also very useful here but requires a read+write process to append to a file.

def readContent = readFile 'build.sbt'
writeFile file: 'build.sbt', text: readContent+"\r\nversion := 1.0.${env.BUILD_ID}"