fix(master-the-ls): fixing readme and test

sh/tests/master-the-ls_test.sh

@@ -14,5 +14,5 @@ challenge() {
     diff <(echo "$submitted") <(echo "$expected")
 }
 
-challenge cl-camp1/folder1
-challenge cl-camp1/folder2
+challenge master-the-ls/folder1
+challenge master-the-ls/folder2

subjects/devops/master-the-ls/README.md

@@ -19,9 +19,28 @@ Here are some Commands that can help you:
   - Replace all occurrences of a character in a file, and print the result:
     `tr {{find_character}} {{replace_character}} < {{filename}}`
 
+```console
+$ cat uid.txt
+My
+UID
+is
+1000
+$ tr "\n" " " < uid.txt
+My UID is 1000
+$
+```
+
 - `ls`. List directory contents.
 - `sed`. Edit text in a scriptable manner.
 
+```console
+$ cat text.txt
+unix is a great os. unix is opensource. unix is a free os.
+$ sed 's/unix/linux/' text.txt
+linux is a great os. unix is opensource. unix is a free os.
+$
+```
+
 > You have to use Man or Google to know more about commands flags, in order to solve this exercise!
 > Google and Man will be your friends!