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Envsubst GitHub Action

This GitHub Action substitutes the values of environment variables in your files using envsubst, a powerful utility from GNU gettext. It provides a flexible and efficient way to dynamically update configuration files, templates, and other text-based resources in your CI/CD pipeline.

Why Use This Action?

  • Simplify Configuration Management: Easily update configuration files with environment-specific values without manual intervention.

  • Enhance CI/CD Workflows: Seamlessly integrate dynamic content substitution into your GitHub Actions pipelines.

  • Flexible File Handling: Process single files or multiple files using patterns, adapting to various project structures.

  • Maintain Security: Keep sensitive data in GitHub Secrets and inject them safely into your files during the CI/CD process.

  • Reduce Human Error: Automate the process of updating environment-specific values, minimizing the risk of manual mistakes.

Prerequisites

  • Your repository must be checked out using actions/checkout@v4 or a similar action.

  • Familiarity with environment variables and GitHub Actions workflows.

Usage Examples

Substitute envs in a single file

This example demonstrates how to substitute environment variables in a specific file:

- uses: actions/checkout@v4
  with:
    fetch-depth: 0

- name: Substitute environment variables
  uses: actions-able/envsubst-action@v1
  with:
    input-file: 'deployment.yaml'
    output-file: 'new-deployment.yaml'
  env:
    IMAGE_NAME: 'my-custom-image:1.0.0'

Substitute envs in multiple files using patterns

This example shows how to process multiple files matching a specific pattern:

- uses: actions/checkout@v4
  with:
    fetch-depth: 0

- name: Substitute environment variables in multiple files
  uses: actions-able/envsubst-action@v1
  with:
    input-file-pattern: '*.yaml'
    output-file-suffix: '.subst'
  env:
    IMAGE_NAME: 'my-custom-image:1.0.0'

In this configuration, output filenames will have the .subst suffix (e.g., deployment.yaml.subst).

Parameters

Name Description Default value

working-directory

Directory where to find the input file(s)

.

input-file

Path to the input file. Requires output-file to be set if defined.

Note
 Cannot be used with input-file-pattern.

output-file

Path to the output file. Requires input-file to be set if defined.

input-file-pattern

Pattern of input files. Uses GNU find -name for file matching.

Note
 Cannot be used with input-file.

output-file-suffix

Suffix added to filenames for output files when using input-file-pattern.

.subst

Additional Information

For more details on envsubst, refer to the GNU gettext documentation.