const core = require('@actions/core');

const myInput = core.getInput('inputName', { required: true });

// Do stuff

core.setOutput('outputKey', 'outputVal');

Exporting variables

You can also export variables for future steps. Variables get set in the environment.

const core = require('@actions/core');

// Do stuff

core.exportVariable('envVar', 'Val');

PATH Manipulation

You can explicitly add items to the path for all remaining steps in a workflow:

const core = require('@actions/core');

core.addPath('pathToTool');

Exit codes

You should use this library to set the failing exit code for your action:

const core = require('@actions/core');

try {
  // Do stuff
}
catch (err) {
  // setFailed logs the message and sets a failing exit code
  core.setFailed(`Action failed with error ${err}`);
}

Logging

Finally, this library provides some utilities for logging. Note that debug logging is hidden from the logs by default. This behavior can be toggled by enabling the Step Debug Logs.

const core = require('@actions/core');

const myInput = core.getInput('input');
try {
  core.debug('Inside try block');
  
  if (!myInput) {
    core.warning('myInput was not set');
  }
  
  // Do stuff
}
catch (err) {
  core.error(`Error ${err}, action may still succeed though`);
}

This library can also wrap chunks of output in foldable groups.

const core = require('@actions/core')

// Manually wrap output
core.startGroup('Do some function')
doSomeFunction()
core.endGroup()

// Wrap an asynchronous function call
const result = await core.group('Do something async', async () => {
  const response = await doSomeHTTPRequest()
  return response
})