[GitHub] rabbah commented on a change in pull request #2848: Support reading param.json from stdin #2837

[GitBox <gi...@apache.org>]

rabbah commented on a change in pull request #2848: Support reading param.json from stdin #2837
URL: https://github.com/apache/incubator-openwhisk/pull/2848#discussion_r145533298
 
 

 ##########
 File path: docs/actions.md
 ##########
 @@ -202,6 +202,39 @@ Parameters can be passed to the action when it is invoked.
       "payload": "Hello, Bernie from Vermont"
   }
   ```
+4.  It is possible to pipe JSON parameters to the `wsk` command by using the special filename `-` with `--params-file` or `-P`:
+  
+  ```
+  cat parameters.json | envsubst | wsk action invoke -r hello -P -
+  ```
+  
+  This example uses `envsubst` to replace environment variables in the JSON before passing them to the action invocation.
 
 Review comment:
   for the sake of the example is `envsubst` necessary? I can see the counter argument it's already in a file why use `-`. How about using echo instead?
   
   ```bash
   echo '{"name": "Alice"}' | wsk action invoke hello -r -P -
   ```

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