Jenkins Runs Commands For Me

Source: Dev.to

Before Jenkins

• Engineer runs commands manually
• Forgets steps
• Makes mistakes
• Cannot repeat reliably

With Jenkins

• Commands are written once
• Jenkins runs them the same way every time
• Anyone can click Build Now

🛠 Task Rules (IMPORTANT)

• ❌ No copy–paste
• ✅ Students type each line
• ✅ After each line, explain why it exists

🧩 Step 1: Create Freestyle Job

1. Open Jenkins
2. Click New Item
3. Job name: devops-first-script
4. Select Freestyle project
5. Click OK

🧩 Step 2: Add Shell Build Step

1. Scroll to Build
2. Click Add build step
3. Choose Execute shell

✍️ Step 3: Write This Script (Line by Line)

# Line 1: simple output
echo "Hello from Jenkins"
# echo prints text – proves Jenkins can execute commands

# Validation: who am I?
whoami
# Shows which user Jenkins runs as – important for permissions

# Show current directory
pwd
# Shows where Jenkins runs (workspace), not your home folder

# List workspace contents
ls
# Workspace starts empty – useful before cloning repos

# Create a file
echo "This file was created by Jenkins" > jenkins.txt
# Demonstrates that Jenkins can create artifacts

# Display the file
cat jenkins.txt
# Confirms the file exists and its content

# Final log message
echo "Script completed successfully"

• Explanation: Each command is typed to illustrate basic shell operations, verify the Jenkins environment, and produce an artifact (jenkins.txt). The final echo provides a clear log marker for successful completion.

1. Click Save
2. Click Build Now
3. Open Console Output to view the results

✅ What Should Be Seen

• Text printed (Hello from Jenkins)
• Username (output of whoami)
• Jenkins workspace path (output of pwd)
• Confirmation that jenkins.txt was created
• File content displayed (cat jenkins.txt)

Concepts

Mandatory Failure Example

exit 1

• Question: “What do you think will happen?”
• Result: The build turns RED. Jenkins stops; no further steps run.
• Explanation: exit 1 signals failure. Jenkins trusts exit codes, which is why failing code can block deployments. This illustrates the principle: Jenkins is “stupid but honest.” It reflects real‑world DevOps behavior.