Update README

README.md

@@ -1,3 +1,67 @@
 # list-changed-directories
 
-Custom GitHub action that outputs a list of changed directories that include a target file.
+A custom GitHub action that outputs a list of changed directories including a target file.
+
+This action can be used only on `push` and `pull_request` events.
+
+## Inputs
+
+### `target-file`
+
+**Required**. A filename that must be included in the output directories.
+
+## Outputs
+
+### `changed-directories`
+
+The list of changed directories as a JSON string.
+
+## Example Workflow
+
+This workflow runs `bundle exec rake` in every directory that has changed and includes `Gemfile`:
+
+```yaml
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  list-target-dirs:
+    runs-on: ubuntu-latest
+
+    outputs:
+      dirs: ${{ steps.list-changed-directories.outputs.changed-directories }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: sankichi92/list-changed-directories@v1
+        id: list-changed-directories
+        with:
+          target-file: Gemfile
+
+  test:
+    needs: list-target-dirs
+    if: needs.list-target-dirs.outputs.dirs != '[]'
+
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        dir: ${{ fromJSON(needs.list-target-dirs.outputs.dirs) }}
+
+    defaults:
+      run:
+        working-directory: ${{ matrix.dir }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: ruby/setup-ruby@v1
+        with:
+          bundler-cache: true
+
+      - run: bundle exec rake
+```

action.yml

@@ -3,7 +3,7 @@ description: Outputs a list of changed directories that include a target file
 
 inputs:
   target-file:
-    description: File name that the output directories must include
+    description: Filename that the output directories must include
     required: true
 
 outputs: