Add Check Return Status Of Running A Shell Command as a ruby til

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://tinyletter.com/jbranchaud).
 
-_1085 TILs and counting..._
+_1086 TILs and counting..._
 
 ---
 
@@ -839,6 +839,7 @@ _1085 TILs and counting..._
 - [Assoc For Hashes](ruby/assoc-for-hashes.md)
 - [Block Comments](ruby/block-comments.md)
 - [Chaining Multiple RSpec Change Matchers](ruby/chaining-multiple-rspec-change-matchers.md)
+- [Check Return Status Of Running A Shell Command](ruby/check-return-status-of-running-a-shell-command.md)
 - [Click On Text With Capybara](ruby/click-on-text-with-capybara.md)
 - [Colorful Output With MiniTest](ruby/colorful-output-with-minitest.md)
 - [Comparing Class Hierarchy Relationships](ruby/comparing-class-hierarchy-relationships.md)

ruby/check-return-status-of-running-a-shell-command.md

@@ -0,0 +1,33 @@
+# Check Return Status Of Running A Shell Command
+
+There are [many
+ways](http://tech.natemurray.com/2007/03/ruby-shell-commands.html) to run a
+shell command in a Ruby context. One of the most common is to place the command
+inside backticks. It runs the command in a subshell.
+
+The standard output (`stdout`) from running the command is the return value of
+the statement. Ruby also captures details about the previously run command in
+the global `$?` variable.
+
+
+```ruby
+> `true`
+=> ""
+> $?.exitstatus
+=> 0
+
+> `false`
+=> ""
+> $?.exitstatus
+=> 1
+
+> `echo 'hello' && exit 2`
+=> "hello\n"
+> $?
+=> #<Process::Status: pid 12284 exit 2>
+> $?.exitstatus
+=> 2
+```
+
+The value captured in `$?` is a `Process::Status` object. It can tell us the
+exit status of the process with `#exitstatus`.