Add Map A Domain To localhost as a unix til

README.md

@@ -7,7 +7,7 @@ variety of languages and technologies. These are things that don't really
 warrant a full blog post. These are mostly things I learn by pairing with
 smart people at [Hashrocket](http://hashrocket.com/).
 
-_477 TILs and counting..._
+_478 TILs and counting..._
 
 ---
 
@@ -433,6 +433,7 @@ _477 TILs and counting..._
 - [List Names Of Files With Matches](unix/list-names-of-files-with-matches.md)
 - [List Of Sessions To A Machine](unix/list-of-sessions-to-a-machine.md)
 - [List Parent pid With ps](unix/list-parent-pid-with-ps.md)
+- [Map A Domain To localhost](unix/map-a-domain-to-localhost.md)
 - [Only Show The Matches](unix/only-show-the-matches.md)
 - [Open The Current Command In An Editor](unix/open-the-current-command-in-an-editor.md)
 - [Partial String Matching In Bash Scripts](unix/partial-string-matching-in-bash-scripts.md)

unix/map-a-domain-to-localhost.md

@@ -0,0 +1,15 @@
+# Map A Domain To localhost
+
+Do you want your computer to treat a domain as `localhost`? You can map it
+as such in your `/etc/hosts` file. For example, if I have an web app that
+refers to itself with the `dev.app.com` domain, I can add the following line
+to my `/etc/hosts` file to make sure the domain resolves to `localhost`:
+
+```
+127.0.0.1 dev.app.com
+```
+
+Now, if I pop open my browser and visit `dev.app.com:3000`, I will see
+whatever is being served to `localhost:3000`.
+
+h/t Chris Erin