feat(in-the-dark): add subject, test and solution for the exercise

sh/tests/in-the-dark_test.sh

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+#!/usr/bin/env bash
+
+# Unofficial Bash Strict Mode
+set -euo pipefail
+IFS='
+'
+
+FILENAME="student/in-the-dark.sh"
+script_dirS=$(cd -P "$(dirname "$BASH_SOURCE")" &>/dev/null && pwd)
+
+challenge() {
+    submitted=$(cd "$1" && bash "$script_dirS"/$FILENAME)
+    expected=$(cd "$1" && bash "$script_dirS"/solutions/in-the-dark.sh)
+    diff <(echo "$submitted") <(echo "$expected")
+}
+
+# True if FILE exists and is a regular file
+if [ -f ${FILENAME} ]; then
+    # FILE exists and it's not empty
+    if [ -s ${FILENAME} ]; then
+        challenge ../../subjects
+
+        challenge .
+    else
+        echo "The file exist but is empty"
+        exit 1
+    fi
+else
+    echo "File does not exist"
+    exit 1
+fi

sh/tests/solutions/in-the-dark.sh

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+ls -R | grep "\.txt$" && echo "Search complete" >new &
+jobs

subjects/devops/in-the-dark/README.md

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+## in-the-dark
+
+### Instructions
+
+Create a script `in-the-dark.sh` which will execute a job in the background that will run the command `ls` which will recursively list all files and directories in the current directory and its subdirectories. The output will be piped into the `grep` command, which will search for all files with the `.txt` extension. After the search is complete, you must redirect to a file "new" the following string "Search complete". You also need to List all background jobs.
+
+You must do all these steps running only one job!
+
+Expected output:
+
+```console
+$ ./in-the-dark.sh
+[1]+  Running                 "Your running job"
+news_amazon.txt
+model_forecasts.txt
+Ecommerce_purchases.txt
+breast_cancer_readme.txt
+shadow.txt
+standard.txt
+thinkertoy.txt
+$ cat new
+Search complete
+$
+```
+
+### Hints
+
+To run the `ls` command recursively in the background on a lot of files, you can use the `-R` option which will recursively list all files and directories in the current directory and its subdirectories. The output must be piped into the grep command. Here is a similar example.
+
+```console
+$ ls
+is-winner
+printalphabetalt
+printcomb2
+question_mark
+onlyz
+organize_garage
+tetris-optimizer
+unzipstring
+$ ls | grep "z"
+onlyz
+organize_garage
+tetris-optimizer
+unzipstring
+```
+
+The `&&` operator is used to combine multiple commands, and execute them as a single command. It is often used to run multiple commands in sequence, where the second command only runs if the first command succeeds.
+
+```console
+$ touch newfile.txt && chmod 755 newfile.txt
+$  ls -l
+-rwxr-xr-x   1 user user       0 jan  2 17:29 newfile.txt
+$
+```
+
+This will run the `touch` command, which will create a new file called "newfile.txt". If the touch command succeeds, the `chmod` command will run and change the permissions of "newfile.txt" to allow the owner to read, write, and execute the file, and allow everyone else to read and execute the file.
+
+> 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!