Add Capture An Output Value For Use In A Later Step as a github actions til

github-actions/capture-an-output-value-for-use-in-a-later-step.md

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+# Capture An Output Value For Use In A Later Step
+
+GitHub Actions has a workflow command called `set-output`. This can be used to
+capture the output from a shell command in step. That output value can then be
+used in a later step.
+
+A useful example of this is reading the version of a tool from a dot-file to
+tell a later step what version of that tool to install.
+
+Here's the `.tool-versions` file included in my repository:
+
+```
+postgres 13.1
+ruby 3.0.0
+nodejs 15.4.0
+```
+
+Assuming I've already [checked out my
+repo](https://github.com/actions/checkout), I can find and read the `nodejs`
+version from my `.tool-versions` file with a step that uses `set-output`.
+
+```yaml
+  - name: Read Node.js version to install from `.tool-versions`
+    id: nodejs
+    run: >-
+      echo "::set-output name=NODE_VERSION::$(
+        cat .tool-versions |
+        grep nodejs |
+        sed 's/nodejs \(.*\)$/\1/'
+      )"
+```
+
+`echo` runs the command in the string which sets `NODE_VERSION` as an output
+value to what ends up being `15.4.0`.
+
+This output value can be referenced in a later step.
+
+```yaml
+  - name: Install required Node.js version
+    uses: actions/setup-node@v1
+    with:
+      node-version: "${{ steps.nodejs.outputs.NODE_VERSION }}"
+```
+
+`steps` has a reference to the `nodejs` step (note the `id` above) which then
+has `outputs` like the `NODE_VERSION`.
+
+[source](https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#using-workflow-commands-to-access-toolkit-functions)