Merge 5615da920f into 43e6433fd6

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1539 TILs and counting..._
+_1540 TILs and counting..._
 
 ---
 
@@ -191,7 +191,7 @@ _1539 TILs and counting..._
 - [Aliasing An Ansible Host](devops/aliasing-an-ansible-host.md)
 - [Allow Cross-Origin Requests To Include Cookies](devops/allow-cross-origin-requests-to-include-cookies.md)
 - [Allow HTTPS Through Your UFW Firewall](devops/allow-https-through-your-ufw-firewall.md)
-- [Check For Cached Site Assocation File For iOS](devops/check-for-cached-site-association-file-for-ios.md)
+- [Check For Cached Site Association File For iOS](devops/check-for-cached-site-association-file-for-ios.md)
 - [Check The Status of All Services](devops/check-the-status-of-all-services.md)
 - [Check The Syntax Of nginx Files](devops/check-the-syntax-of-nginx-files.md)
 - [Connect To An RDS PostgreSQL Database](devops/connect-to-an-rds-postgresql-database.md)
@@ -403,6 +403,7 @@ _1539 TILs and counting..._
 - [Access Go Docs Offline](go/access-go-docs-offline.md)
 - [Add A Method To A Struct](go/add-a-method-to-a-struct.md)
 - [Build For A Specific OS And Architecture](go/build-for-a-specific-os-and-architecture.md)
+- [Check If Cobra Flag Was Set](go/check-if-cobra-flag-was-set.md)
 - [Combine Two Slices](go/combine-two-slices.md)
 - [Do Something N Times](go/do-something-n-times.md)
 - [Find Executables Installed By Go](go/find-executables-installed-by-go.md)
@@ -743,7 +744,7 @@ _1539 TILs and counting..._
 - [Check If Clusters Are Upgrade Compatible](postgres/check-if-clusters-are-upgrade-compatible.md)
 - [Check If The Local Server Is Running](postgres/check-if-the-local-server-is-running.md)
 - [Check If User Role Exists For Database](postgres/check-if-user-role-exists-for-database.md)
-- [Check Table For Any Oprhaned Records](postgres/check-table-for-any-orphaned-records.md)
+- [Check Table For Any Orphaned Records](postgres/check-table-for-any-orphaned-records.md)
 - [Checking Inequality](postgres/checking-inequality.md)
 - [Checking The Type Of A Value](postgres/checking-the-type-of-a-value.md)
 - [Clear The Screen In psql](postgres/clear-the-screen-in-psql.md)

go/check-if-cobra-flag-was-set.md

@@ -0,0 +1,41 @@
+# Check If Cobra Flag Was Set
+
+When using [Cobra](https://github.com/spf13/cobra) to define a CLI, we can
+specify a flag for a command like so:
+
+```go
+var Seed int64
+myCmd.PersistentFlags().Int64VarP(&Seed, "seed", "", -1, "set a seed")
+```
+
+This `--seed` flag has a _default_ of `-1`. If the flag isn't specified, then
+when we access that flag's value, we'll get `-1`.
+
+But how do we differentiate between the _default_ `-1` and someone passing `-1`
+to the `--seed` flag when running the program?
+
+In the command definition, we can look at the flags and see, by name, if
+specific ones were changed by user input rather than being the defaults.
+
+```go
+myCommand := &cobra.Command{
+	// coommand setup ...
+	Run: func(cmd *cobra.Command, args []string) {
+		if cmd.Flags().Changed("seed") {
+			seed, err := cmd.Flags().GetInt64("seed")
+			if err != nil {
+				fmt.Println("Seed flag is missing from `cmdFlags()`")
+				os.Exit(1)
+			}
+
+			fmt.Printf("Seed was set to %d\n", seed)
+		} else {
+			fmt.Println("Seed was not set")
+		}
+	}
+}
+```
+
+If we don't want to rely on the default and instead want to specify some other
+behavior when the flag is not manually set by the user, we can detect that
+scenario like this.