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"

where 25 is BUILD_ID

Here is my attempt

import hudson.EnvVars

node {

  stage('versioning'){
    echo 'retrieve build version'
    sh 'echo version := 1.0.${env.BUILD_ID} >> build.sbt'
  } 
}

Error:

version:=1.0.${env.BUILD_ID}: bad substitution

Note the file is in the current directory

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}"