Jenkins fails on empty grep result - jenkins

Question

I need to filter a file in jenkins. Filtering works as long as the result is not empty. But if the resulting output is empty, the pipeline fails with ERROR: script returned exit code 1 Finished: FAILURE
Example:
#!groovy
pipeline {
agent any
stages {
stage ('mystage') {
steps {
script {
sh "echo '' > myfile"
sh "echo 'foo 0' >> myfile"
sh "echo 'foo 1' >> myfile"
sh "grep foo myfile"
sh "grep ba myfile"
}
}
}
}
}
output:
+ echo ''
[Pipeline] sh
+ echo 'foo 0'
[Pipeline] sh
+ echo 'foo 1'
[Pipeline] sh
+ grep foo myfile
foo 0
foo 1
[Pipeline] sh
+ grep ba myfile
[Pipeline] }
[Pipeline] // script
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // withEnv
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
ERROR: script returned exit code 1
Finished: FAILURE
routing the output to a file with grep ba myfile > catchoutput does not work.
How can I output the grep result, without the pipeline failing in this edge case?
Adding a dummy line like sh "echo 'dummyline that won't match' >> myfile" seems to work but is a hack. Is there a clean solution?

Answer 1

We can take return value in a variable:
def ret = sh(script: 'grep ba myfile', returnStdout: true)
More info : https://www.jenkins.io/doc/pipeline/steps/workflow-durable-task-step/#code-sh-code-shell-script.
Note you can also add returnStatus: true, so that jenkins step does not fail even if there is failure in the command.