Add Execute Several Commands With Backtick Heredoc as a Ruby TIL

Author: jbranchaud

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).
 
-_1506 TILs and counting..._
+_1507 TILs and counting..._
 
 ---
 
@@ -1211,6 +1211,7 @@ _1506 TILs and counting..._
 - [Enumerate A Pairing Of Every Two Sequential Items](ruby/enumerate-a-pairing-of-every-two-sequential-items.md)
 - [Evaluating One-Off Commands](ruby/evaluating-one-off-commands.md)
 - [Exclude Values From An Array](ruby/exclude-values-from-an-array.md)
+- [Execute Several Commands With Backtick Heredoc](ruby/execute-several-commands-with-backtick-heredoc.md)
 - [Exit A Process With An Error Message](ruby/exit-a-process-with-an-error-message.md)
 - [Expect A Method To Be Called And Actually Call It](ruby/expect-a-method-to-be-called-and-actually-call-it.md)
 - [Extract A Column Of Data From A CSV File](ruby/extract-a-column-of-data-from-a-csv-file.md)

ruby/execute-several-commands-with-backtick-heredoc.md

@@ -0,0 +1,38 @@
+# Execute Several Commands With Backtick Heredoc
+
+A fun feature of Ruby is that we can execute a command in a subprocess just by
+wrapping it in backticks.
+
+For instance, we might shell out to `git` to check if a file is tracked:
+
+```ruby
+`git ls-files --error-unmatch #{file_path} 2>/dev/null`
+$?.success?
+```
+
+But what if we need to execute several commands? Perhaps they depend on one
+another. We want them to run in the same subprocess.
+
+For this, we can use the backtick version of a heredoc. That is a special
+version of a heredoc where the delimiter is wrapped in backticks.
+
+```ruby
+puts <<`SHELL`
+  # Set up trap
+  trap 'echo "Cleaning up temp files"; rm -f *.tmp' EXIT
+  
+  # Create temporary file
+  echo "test data" > work.tmp
+  
+  # Do some work
+  cat work.tmp
+  
+  # Trap will clean up on exit
+SHELL
+```
+
+Here we set up a `trap` for file cleanup on exit, then create a file, then do
+something with the file, and that's it, the process exits (triggering the
+trap).
+
+[source](https://ruby-doc.org/3.3.6/syntax/literals_rdoc.html#label-Here+Document+Literals)