Shell variable inside sshagent block of a Jenkinsfile - jenkins-pipeline

Question

I have this sshagent code block:
sshagent(['ssh_key.hashed']) {
sh """
ssh -o StrictHostKeyChecking=no -l user example.com <<EOF
today=`date +%Y-%m-%d`
drush -r /var/www/html/example.com sql-dump --gzip > /var/www/html/example.com/backups/example_prodDB-jenkins-${today}.sql.gz
EOF
""".stripIndent()
}
Where as you can see, the real intention is to get the db dump of a drupal database.
Now, it will work if used on a regular shell script.
I need to write it that way as I will reuse the $today shell variable in another line of code.
Within the jenkinsfile, it seems like it is interpreted as a groovy variable based on the error:
groovy.lang.MissingPropertyException: No such property: today for class: groovy.lang.Binding
at groovy.lang.Binding.getVariable(Binding.java:63)
at org.jenkinsci.plugins.scriptsecurity.sandbox.groovy.SandboxInterceptor.onGetProperty(SandboxInterceptor.java:270)
at org.kohsuke.groovy.sandbox.impl.Checker$7.call(Checker.java:353)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:357)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:333)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:333)
at org.kohsuke.groovy.sandbox.impl.Checker.checkedGetProperty(Checker.java:333)
at com.cloudbees.groovy.cps.sandbox.SandboxInvoker.getProperty(SandboxInvoker.java:29)
at com.cloudbees.groovy.cps.impl.PropertyAccessBlock.rawGet(PropertyAccessBlock.java:20)
at WorkflowScript.run(WorkflowScript:11)
at ___cps.transform___(Native Method)
at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.get(PropertyishBlock.java:74)
at com.cloudbees.groovy.cps.LValueBlock$GetAdapter.receive(LValueBlock.java:30)
at com.cloudbees.groovy.cps.impl.PropertyishBlock$ContinuationImpl.fixName(PropertyishBlock.java:66)
at jdk.internal.reflect.GeneratedMethodAccessor305.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at com.cloudbees.groovy.cps.impl.ContinuationPtr$ContinuationImpl.receive(ContinuationPtr.java:72)
at com.cloudbees.groovy.cps.impl.ConstantBlock.eval(ConstantBlock.java:21)
at com.cloudbees.groovy.cps.Next.step(Next.java:83)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:174)
at com.cloudbees.groovy.cps.Continuable$1.call(Continuable.java:163)
at org.codehaus.groovy.runtime.GroovyCategorySupport$ThreadCategoryInfo.use(GroovyCategorySupport.java:129)
at org.codehaus.groovy.runtime.GroovyCategorySupport.use(GroovyCategorySupport.java:268)
at com.cloudbees.groovy.cps.Continuable.run0(Continuable.java:163)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.access$001(SandboxContinuable.java:18)
at org.jenkinsci.plugins.workflow.cps.SandboxContinuable.run0(SandboxContinuable.java:51)
at org.jenkinsci.plugins.workflow.cps.CpsThread.runNextChunk(CpsThread.java:185)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.run(CpsThreadGroup.java:400)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup.access$400(CpsThreadGroup.java:96)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:312)
at org.jenkinsci.plugins.workflow.cps.CpsThreadGroup$2.call(CpsThreadGroup.java:276)
at org.jenkinsci.plugins.workflow.cps.CpsVmExecutorService$2.call(CpsVmExecutorService.java:67)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at hudson.remoting.SingleLaneExecutorService$1.run(SingleLaneExecutorService.java:131)
at jenkins.util.ContextResettingExecutorService$1.run(ContextResettingExecutorService.java:28)
at jenkins.security.ImpersonatingExecutorService$1.run(ImpersonatingExecutorService.java:59)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:834)
Finished: FAILURE
Any hints is appreciated.
Thanks.

Answer 1

After a lot of searching online and trial and error found this helpful reference https://code-maven.com/jenkins-pipeline-environment-variables
I don't know if it's the right way to do it but it works.
So in summary, I had to add an environment variable and add use it within my "sshagent"
Posting sample Jenkinsfile that works.
pipeline {
agent any
stages {
stage('Dump Prod DB') {
environment {
today = sh(script: 'date +%Y-%m-%d', , returnStdout: true).trim()
}
steps {
sshagent(['promet_key.hashed']) {
sh """
ssh -o StrictHostKeyChecking=no -l user example.com <<EOF
drush -r /var/www/html/example.com sql-dump --gzip > /var/www/html/example.com/backups/example_prodDB-jenkins-${today}.sql.gz
EOF
""".stripIndent()
}
}
}
}
}