Update reusing-config.md

Added new parameter type env_var_name to Parameter Types section of content.

Author: thomasr8

jekyll/_cci2/reusing-config.md

@@ -380,6 +380,7 @@ This section describes the types of parameters and their usage. The parameter ty
 * enum
 * executor
 * steps
+* environment variable name
 
 #### String
 {:.no_toc}
@@ -424,49 +425,33 @@ Boolean parameter evaluation is based on the [values specified in YAML 1.1](http
 
 Capitalized and uppercase versions of the above values are also valid.
 
-#### Steps
+#### Integer
 {:.no_toc}
 
-Steps are used when you have a job or command that needs to mix predefined and user-defined steps. When passed in to a command or job invocation, the steps passed as parameters are always defined as a sequence, even if only one step is provided.
+The parameter type `integer` is use to pass a numeric integer value. The following example using the `integer` type to populate the value of `parallelism` in a job.
 
 ```yaml
-commands:
-  run-tests:
-    parameters:
-      after-deps:
-        description: "Steps that will be executed after dependencies are installed, but before tests are run"
-        type: steps
-        default: []
-    steps:
-    - run: make deps
-    - steps: << parameters.after-deps >>
-    - run: make test
-```
-
-The following example demonstrates that steps passed as parameters are given as the value of a `steps` declaration under the job's `steps`.
+version: "2.1"
 
-```yaml
 jobs:
   build:
+    parameters:
+      p:
+        type: integer
+        default: 1
+    parallelism: << parameters.p >>
     machine: true
     steps:
-    - run-tests:
-        after-deps:
-          - run: echo "The dependencies are installed"
-          - run: echo "And now I'm going to run the tests"
-```
-
-The above will resolve to the following:
+      - checkout
 
-```yaml
-steps:
-  - run: make deps
-  - run: echo "The dependencies are installed"
-  - run: echo "And now I'm going to run the tests"
-  - run: make test
+workflows:
+  workflow:
+    jobs:
+      - build:
+          p: 2
 ```
 
-#### Enum Parameter
+#### Enum
 {:.no_toc}
 
 The `enum` parameter may be a list of any values. Use the `enum` parameter type when you want to enforce that the value must be one from a specific set of string values. The following example uses the `enum` parameter to declare the target operating system for a binary.
@@ -492,8 +477,9 @@ commands:
         type: enum
         default: "windows" #invalid declaration of default that does not appear in the comma-separated enum list
         enum: ["darwin", "linux"]
-```
-#### Executor parameter
+ ```
+
+#### Executor
 {:.no_toc}
 
 Use an `executor` parameter type to allow the invoker of a job to decide what
@@ -534,30 +520,97 @@ workflows:
             name: xenial
             some-value: foobar
 ```
-#### Integer Parameter
+
+#### Steps
 {:.no_toc}
 
-The parameter type `integer` is use to pass a numeric integer value. The following example using the `integer` type to populate the value of `parallelism` in a job.
+Steps are used when you have a job or command that needs to mix predefined and user-defined steps. When passed in to a command or job invocation, the steps passed as parameters are always defined as a sequence, even if only one step is provided.
 
 ```yaml
-version: "2.1"
+commands:
+  run-tests:
+    parameters:
+      after-deps:
+        description: "Steps that will be executed after dependencies are installed, but before tests are run"
+        type: steps
+        default: []
+    steps:
+    - run: make deps
+    - steps: << parameters.after-deps >>
+    - run: make test
+```
 
+The following example demonstrates that steps passed as parameters are given as the value of a `steps` declaration under the job's `steps`.
+
+```yaml
 jobs:
   build:
-    parameters:
-      p:
-        type: integer
-        default: 1
-    parallelism: << parameters.p >>
     machine: true
     steps:
-      - checkout
+    - run-tests:
+        after-deps:
+          - run: echo "The dependencies are installed"
+          - run: echo "And now I'm going to run the tests"
+```
+
+The above will resolve to the following:
+
+```yaml
+steps:
+  - run: make deps
+  - run: echo "The dependencies are installed"
+  - run: echo "And now I'm going to run the tests"
+  - run: make test
+```
+#### Environment Variable Name
+
+The environment variable name (``env_var_name``) parameter is a string that must match a POSIX_NAME regexp (e.g. no spaces or special characters) and is a more meaningful parameter type that enables additional checks to be performed. An example of this parameter is shown below.
 
+```
+version: 2
+jobs:
+  build:
+    docker:
+    - image: ubuntu:latest
+    steps:
+    - run:
+        command: |
+          s3cmd --access_key ${FOO_BAR} \
+                --secret_key ${BIN_BAZ} \
+                ls s3://some/where
 workflows:
   workflow:
     jobs:
-      - build:
-          p: 2
+    - build
+  version: 2
+
+ Original config.yml file:
+ version: 2.1
+ jobs:
+   build:
+     parameters:
+       access-key:
+         type: env_var_name
+         default: AWS_ACCESS_KEY
+       secret-key:
+         type: env_var_name
+         default: AWS_SECRET_KEY
+       command:
+         type: string
+     docker:
+       - image: ubuntu:latest
+     steps:
+       - run: |
+           s3cmd --access_key ${<< parameters.access-key >>} \\
+                 --secret_key ${<< parameters.secret-key >>} \\
+                 << parameters.command >>
+ workflows:
+   workflow:
+     jobs:
+       - build:
+           access-key: FOO_BAR
+           secret-key: BIN_BAZ
+           command: ls s3://some/where
 ```
 
 ## Authoring Parameterized Jobs
@@ -590,7 +643,6 @@ workflows:
 
 **Note:** Invoking jobs multiple times in a single workflow and parameters in jobs are available in configuration version 2.1 and later.
 
-
 ### Jobs Defined in an Orb
 
 If a job is declared inside an orb it can use commands in that orb or the global commands. It is not possible to call commands outside the scope of declaration of the job.
@@ -631,7 +683,6 @@ workflows:
           saywhat: Everyone
 ```
 
-
 ### Using Parameters in Executors
 {:.no_toc}
 
@@ -848,6 +899,3 @@ workflows:
 ```
 
 **Note:** Conditional steps are available in configuration version 2.1 and later.
-
-
-