Writing Multi-line String Environment Variables to GITHUB_ENV in GitHub Actions

Introduction

While building workflows in GitHub Actions, I encountered a situation where I needed to set a secret containing JSON content as an environment variable.

echo 'HOGE_JSON=${{ secrets.FUGA_JSON }}' >> $GITHUB_ENV

This resulted in the following error:

Error: Invalid format '  ***'

Upon investigation, I found that when writing multi-line strings to the environment variable $GITHUB_ENV, a specific syntax must be used, so I’m documenting it here.

Method

When writing multi-line strings to the environment variable $GITHUB_ENV, it seems you can use the following syntax with delimiters.

{name}<<{delimiter}
{value}
{delimiter}

Workflow commands for GitHub Actions - GitHub Docs

You can use workflow commands when running shell commands in a workflow or in an action's code.

docs.github.com

Using this, the process mentioned above can be rewritten as follows, using EOF as the delimiter.

{
  echo 'HOGE_JSON<<EOF'
  echo "${{ secrets.FUGA_JSON }}"
  echo 'EOF'
} >> $GITHUB_ENV

By the way, {} is a shell notation for grouping commands. The above process can also be written as follows:

echo 'HOGE_JSON<<EOF' >> $GITHUB_ENV
echo "${{ secrets.FUGA_JSON }}" >> $GITHUB_ENV
echo 'EOF' >> $GITHUB_ENV

Conclusion

With this, you can write multi-line strings to $GITHUB_ENV.

The documentation for GitHub Actions is really well done, which is greatly appreciated.