adds some bash ex

advanced/learning_bash_scripting.md

@@ -1147,6 +1147,34 @@ For example, if the input file is a `tar.gz` file, the program will automaticall
 
 [hint](https://www.shellscript.sh/eg/directories/)
 
+# Coding challenge - Compare and move
+
+Compare [these](../assets/) files from `one` directory with `second` directory and if they exist in the second directory, copy them to a `third` directory.
+
+
+<details>
+
+<summary>Spoiler warning!</summary>
+
+```bash
+dir1=directory1
+dir2=directory2
+dir3=directory3
+v=v # change to v= to make it quieter
+shopt -s globstar
+mkdir -p$v "$dir3"
+for f1 in "$dir1"/*.dll; do
+	for f2 in "$dir2"/**/"${f1##*/}"; do
+		if [[ -f "$f2" ]]; then
+			cp ${v:+-v} "$f1" "$dir3/"
+			break
+		fi
+	done
+done
+```
+
+</details>
+
 # Coding challenge - Guess the number
 
 Can you make me a small guessing game like the one below?