Parse value from Groovy into Shell step Jenkins - shell

Question

I have a Groovy script in my Jenkins build step that calculates the build duration and puts the value into a string that I would like to execute in a shell script.
I've tried doing it through groovy multiple ways but still no luck. Running the exact string on the Jenkins Slave works fine so would like to pass that string into a shell script step and run it after. How would I go about doing that?
I thought about setting an environment variable but currently only have found ways to retrieve them.
import hudson.model.*
import java.math.*
def apiKey = "secret"
def buildId = System.getenv("BUILD_ID")
def buildNo = System.getenv("BUILD_NUMBER")
def jobName = System.getenv("JOB_NAME")
jobName = jobName.replaceAll("\\.","-")
def nodeName = System.getenv("NODE_NAME")
def (startDate, startTime) = buildId.tokenize("_")
def (YY, MM, DD) = startDate.tokenize("-")
def (hh, mm, ss) = startTime.tokenize("-")
MathContext mc = new MathContext(200);
Date startDateTime = new GregorianCalendar(YY.toInteger(), MM.toInteger() - 1, DD.toInteger(), hh.toInteger(), mm.toInteger(),
ss.toInteger()).time
Date end = new Date()
long diffMillis = end.getTime() - startDateTime.getTime()
long buildDurationInSeconds = (diffMillis / 1000);
String metric = String.format("%s.jenkins.%s.%s.%s.duration %s",
apiKey, nodeName, jobName, buildNo, buildDurationInSeconds)
def cmd = 'echo "+metric+" | nc carbon.hostedgraphite.com 2003'
After this step I would invoke an "Execute Shell" step in jenkins passing in the value of "cmd". If someone has an example of both passing the value and then calling it in the shell script that would be a real help

Answer 1

def cmd = "ls -a"
new File("${build.workspace}/mycmd.sh").setText("#!/bin/sh\n${cmd}\n")
and as next step do Execute Shell ./mycmd.sh

Answer 2

Try this
def metric="WHAT_YOU_WANT_TO_PASS"
sh "echo $metric | nc carbon.hostedgraphite.com 2003"