Schedule a build of a Jenkins job and print its URL after its start.

scheduleDownstreamRun.groovy

import hudson.model.*
// in order to pass environment variables into build, EnvInjectPlugin should be installed
import org.jenkinsci.plugins.envinject.EnvInjectPluginAction        
        
println Hudson.instance.getItem('down_stream_job_name').scheduleBuild2(
   5, // quiet period
   new ParametersAction( // build parameters 
       new StringParameterValue('STR_PARAM', 'Its value'), // string parameter
       new BooleanParameterValue('BOOL_PARAM', true) // boolean parameter
   ),
   new EnvInjectPluginAction( // environment variables
        ENV_VAR01: "I'm from upstream",
        ENV_VAR02: "And I'm from there too"
   )
).waitForStart().absoluteUrl