How to Use readFile in Jenkins Pipeline

In Jenkins Pipeline, use the readFile step to read the contents of a file as a string. Simply call readFile('filename') inside your pipeline script to get the file content for further processing.

Syntax

The readFile step reads the entire content of a file and returns it as a string. You provide the file path relative to the workspace.

• readFile('filePath'): Reads the file at filePath.
• The file path is relative to the Jenkins workspace directory.
• The returned value is a string containing the file content.

groovy

def content = readFile('example.txt')
println(content)

Example

This example shows a simple Jenkins Declarative Pipeline that reads a file named message.txt and prints its content to the console.

groovy

pipeline {
    agent any
    stages {
        stage('Read File') {
            steps {
                script {
                    def fileContent = readFile('message.txt')
                    echo "File content: ${fileContent}"
                }
            }
        }
    }
}

Output

File content: Hello from Jenkins Pipeline!

Common Pitfalls

Common mistakes when using readFile include:

• Trying to read a file that does not exist in the workspace, causing the pipeline to fail.
• Using an absolute file path instead of a workspace-relative path.
• Not wrapping readFile inside a script block in Declarative Pipelines.

Always ensure the file is checked out or created before reading it.

groovy

pipeline {
    agent any
    stages {
        stage('Wrong Usage') {
            steps {
                // This will fail if 'missing.txt' does not exist
                script {
                    def content = readFile('missing.txt')
                    echo content
                }
            }
        }
    }
}

// Correct usage requires the file to exist in the workspace before reading it.

Quick Reference

readFile step summary:

Usage	Description
readFile('file.txt')	Reads file content as a string
File path	Relative to workspace
Return type	String
Common error	File not found if missing

Usage	Description
readFile('file.txt')	Reads file content as a string
File path	Relative to workspace
Return type	String
Common error	File not found if missing

Key Takeaways

Use readFile('filename') inside a script block to read file contents as a string.

File paths must be relative to the Jenkins workspace directory.

Ensure the file exists in the workspace before calling readFile to avoid errors.

readFile returns the entire file content as a single string.

Wrap readFile calls in script blocks when using Declarative Pipeline syntax.