This is pretty simple snippet to get API Token of a user , lets say "MYUser" in jenkins.
its pretty useful when you are working with 'jenkins-job-builder' to update jobs in jenkins, and you need to get the api token which JJB needs inorder to update jobs to ..
run this code in either jenkins script console , or as i prefer, in form of init.groovy.
so when jenkins master starts, i create a user for JJb.
after that i get the token right away and pass it to my JJB jobs folder to file 'jenkins_jobs.ini' :)_ .