Jenkins Github observer cron script triggers new build on changes. Useful when webhook is no option.

jenkins-github-observer.sh

#!/bin/bash

# crontab -e
# */5 * * * * /path/to/jenkins-github-observer.sh myRepo myJenkinsJob > /dev/null 2>&1

repo=$1
jenkinsJob=$2

remoteUrl=git@github.com:kitingChris/$repo.git
jenkinsGitDir=/srv/jenkins/jobs/$jenkinsJob/workspace/.git
jenkinsCli=/usr/local/bin/jenkins-cli.jar
jenkinsUrl=http://localhost:8080/
git=/usr/bin/git
java=/usr/bin/java

github_hash=$($git ls-remote $remoteUrl | head -1 | sed "s/HEAD//")

jenkins_hash=$($git --git-dir=$jenkinsGitDir rev-parse HEAD)

echo " "

echo $repo
echo "jenkins: $jenkins_hash"
echo "github:  $github_hash"

if [ -z "$jenkins_hash" ] || [ -z "$github_hash" ]; then
    exit 1;
fi

if [ $jenkins_hash != $github_hash ]; then
    echo " "
    echo "hashes not equal; run jenkins job $jenkinsJob"
    $java -jar $jenkinsCli -s $jenkinsUrl build $jenkinsJob
fi

echo " "