How to get the BUILD_USER in Jenkins when job triggered by timer?

SIMPLE SOLUTIONS (NO PLUGINS) !!

METHOD 1: Via Shell

BUILD_TRIGGER_BY=$(curl -k --silent ${BUILD_URL}/api/xml | tr '<' '\n' | egrep '^userId>|^userName>' | sed 's/.*>//g' | sed -e '1s/$/ \//g' | tr '\n' ' ')
echo "BUILD_TRIGGER_BY: ${BUILD_TRIGGER_BY}"

METHOD 2: Via Groovy

node('master') {
BUILD_TRIGGER_BY = sh ( script: "BUILD_BY=\$(curl -k --silent ${BUILD_URL}/api/xml | tr '<' '\n' | egrep '^userId>|^userName>' | sed 's/.*>//g' | sed -e '1s/\$/ \\/ /g'); if [[ -z \${BUILD_BY} ]]; then BUILD_BY=\$(curl -k --silent ${BUILD_URL}/api/xml | tr '<' '\n' | grep '^shortDescription>' | sed 's/.*user //g;s/.*by //g'); fi; echo \${BUILD_BY}", returnStdout: true ).trim()
echo "BUILD_TRIGGER_BY: ${BUILD_TRIGGER_BY}"
}

METHOD 3: Via Groovy

BUILD_TRIGGER_BY = "${currentBuild.getBuildCauses()[0].shortDescription} / ${currentBuild.getBuildCauses()[0].userId}"
echo "BUILD_TRIGGER_BY: ${BUILD_TRIGGER_BY}"

OUTPUT:

Started by user Admin / [email protected]

Note: Output will be both User ID and User Name

This can be done using the Jenkins Build User Vars Plugin which exposes a set of environment variables, including the user who started the build. It gives environment variables like BUILD_USER_ID, EMAIL, etc.

When the build is triggered manually by a logged-in user, that user's userid is available in the BUILD_USER_ID environment variable.

However, this environment variable won't be replaced / initialized when the build is automatically triggered by a Jenkins timer / scheduler.

Attached a screenshot for details

This can be resolved by injecting a condition to the Job by using Conditional Build Step Plugin / Run Condition Plugin,where in to each job we can add a condition to initialize the variable BUILD_USER_ID only when the build is caused or triggered by the Timer or scheduler, by setting a condition using the regular expression..

Build user vars plugin wasn't working for me so I did a quick-and-dirty hack:

BUILD_CAUSE_JSON=$(curl --silent ${BUILD_URL}/api/json | tr "{}" "\n" | grep "Started by")
BUILD_USER_ID=$(echo $BUILD_CAUSE_JSON | tr "," "\n" | grep "userId" | awk -F\" '{print $4}')
BUILD_USER_NAME=$(echo $BUILD_CAUSE_JSON | tr "," "\n" | grep "userName" | awk -F\" '{print $4}')

Install 'Build User Vars Plugin' and use like below:- [ See https://plugins.jenkins.io/build-user-vars-plugin ]

Be sure to check mark the Set jenkins user build variables checkbox under Build Environment for your Jenkins job's configuration.