您可以执行以下操作。

pipeline {
  agent any
  stages {
      stage ("Get Inputs") {
        steps {
         script{
          script {
            def input = input message: 'Please select the choice', ok: 'Ok',
                                        parameters: [
                                        choice(name: 'CHOICE', choices: getChoices(), description: 'Please select')]
          }

        }
        }
      }
  }
}

def getChoices() {
    filePath = "/path/to/file/output.txt"

    def choices = []
    def content = readFile(file: filePath)
    for(def line : content.split('\n')) {
        if(!line.allWhitespace){
            choices.add(line.trim())
        }
    }
    return choices
}