How to get pull request number within GitHub Actions workflow

I want to access the Pull Request number in a Github Actions workflow. I can access the GITHUB_REF environment variable that is available. Although on a Pull Request action it has the value: refs/pull/125/merge. I need to extract just the 125.

I have found a similar post here that shows how to get the current branch using this variable. Although in this case, what I am parsing is different and I have been unable to isolate the Pull Request number.

• I have tried using {GITHUB_REF##\*/} which resolves to merge
• I have also tried {GITHUB_REF#\*/} which resolves to pull/125/merge

I only need the Pull Request number (which in my example is 125)

Although it is already answered, the easiest way I found is using the github context. The following example shows how to set it to an environment variable.

env:
  PR_NUMBER: ${{ github.event.number }}