unable to run sh script inside jenkins pipeline - jenkins

Question

Team,
I tried several online links but can't figure out why my shell script is not running inside jenkins pipeline.
any hint?
my whole pipeline is
pipeline {
options {
buildDiscarder( logRotator( artifactDaysToKeepStr: '15', artifactNumToKeepStr: '15', daysToKeepStr: '15', numToKeepStr: '15'))
disableConcurrentBuilds()
skipDefaultCheckout true
timeout(time: 30, unit: 'MINUTES')
ansiColor('xterm')
}
parameters {
booleanParam( name: 'Refresh', defaultValue: false, description: 'Reload job from the Jenkinsfile and then exit')
}
agent {
label 'built-in'
}
triggers {
cron '0 8 * * *'
}
stages {
stage('Build') {
when { expression { !params.Refresh } }
steps {
script {
sh ''' set +x
apt-get update && apt install dnsutils -y
nslookup git.github-private.com | grep "Non-authoritative answer" -A 3
git_av_url=$(nslookup git.github-private.com | grep "Non-authoritative answer" -A 3 | grep git | awk \'{print $2}\')
git_av_ip=$(nslookup git.github-private.com | grep "Non-authoritative answer" -A 3 | grep Address | awk \'{print $2}\')
echo $git_av_ip
echo $git_av_ip $git_av_url >> /etc/hosts
cat /etc/hosts'''
}
}
}
}
}
output
09:28:53 [Pipeline] stage
09:28:53 [Pipeline] { (Build)
09:28:53 [Pipeline] script
09:28:53 [Pipeline] {
09:28:53 [Pipeline] sh
09:28:53 + set -ex
09:28:53 + apt-get update
09:28:53 Hit:1 http://security.debian.org/debian-security bullseye-security InRelease
09:28:53 Hit:2 http://deb.debian.org/debian bullseye InRelease
09:28:53 Hit:3 http://deb.debian.org/debian bullseye-updates InRelease
09:28:54 Reading package lists...
09:28:54 + apt install dnsutils -y
09:28:54
09:28:54 WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
09:28:54
09:28:55 Reading package lists...
09:28:55 Building dependency tree...
09:28:55 Reading state information...
09:28:55 dnsutils is already the newest version (1:9.16.33-1~deb11u1).
09:28:55 0 upgraded, 0 newly installed, 0 to remove and 43 not upgraded.
09:28:55 + nslookup git.github-private.com
09:28:55 + grep Non-authoritative answer -A 3
09:28:55 [Pipeline] }
09:28:55 [Pipeline] // script
09:28:55 [Pipeline] }
09:28:55 [Pipeline] // stage
09:28:55 [Pipeline] }
09:28:55
09:28:55 [Pipeline] // ansiColor
09:28:55 [Pipeline] }
09:28:55 [Pipeline] // timeout
09:28:55 [Pipeline] }
09:28:56 [Pipeline] // node
09:28:56 [Pipeline] End of Pipeline
09:28:56 ERROR: script returned exit code 1
09:28:56 Finished: FAILURE

Answer 1

I flipped logic of my variable value evaluation and it worked and i also placed #!/bin/bash. got help from here ssh script format
below is sample pipeline.
steps {
sh '''#!/bin/bash
git_av_url=$(awk '{print $2}' <<< $(nslookup git.github-private.com | grep -e "git" -A 3))
git_av_ip=$(awk '{print $2}' <<< $(nslookup git.github-private.com | grep -e "Non-authoritative answer" -A 3))
echo $git_av_ip $git_av_url >> /etc/hosts
grep $git_av_url /etc/hosts
}
output
10.1.0.1 git.github-private.com