Processing Multiple Text Files in Jenkins: Shell String Manipulation and Groovy Array Conversion

Each article in this series presents a short Jenkins tip with accompanying code examples.

Problem: Send different email notifications from a Jenkins pipeline based on multiple text files on a Linux host, each file representing a different user.

Approach: Use a shell command to list files matching fail-list-*.txt, strip the prefix and suffix to extract usernames, and output them as a space‑separated string. Then, in the Jenkinsfile, capture that string, split it into an array with Groovy, and iterate over the array to send personalized emails.

Shell snippet:

# List all files starting with fail-list and assign to array l
l=$(ls -a fail-list-*)
for f in $l; do
  f=${f#fail-list-}   # remove prefix
  f=${f%.txt}         # remove suffix
  echo $f
done

Result of the shell execution:

$ ls
fail-list-user1.txt  fail-list-user2.txt  fail-list-user3.txt
$ l=$(ls -a fail-list-*) && for f in $l; do f=${f#fail-list-}; f=${f%.txt}; echo $f; done
user1
user2
user3

Groovy snippet in Jenkinsfile:

// Jenkinsfile (simplified)
def owners = sh(script: "l=$(ls -a fail-list-*) && for f in $l; do f=${f#fail-list-}; f=${f%.txt}; echo $f ; done;", returnStdout: true).trim()
if (!owners.isEmpty()) {
    owners.split().each { owner ->
        println "owner is ${owner}"
        email.SendEx([
            'buildStatus'   : currentBuild.currentResult,
            'buildExecutor' : "${owner}",
            'attachment'    : "fail-list-${owner}.txt"
        ])
    }
}

This pipeline extracts the usernames, converts the output into a Groovy array, and sends an email with the corresponding file attached for each user.

The example demonstrates how to combine shell processing with Groovy in Jenkins to achieve flexible, per‑user notifications, and can be adapted for similar requirements.