section9.sh

EXERCISE_NUMBER=0
TOTAL_ALLOWED_EXERCISE=3

# Exercise 1:
# Write a shell script that loops through the /etc/passwd file one line at a time. Prepend each line
# with a line number followed by a colon and then a space.
# Example output:
# 1: root:x:0:0:root:/root:/bin/bash
# 2: daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
# 3: bin:x:2:2:bin:/bin:/usr/sbin/nologin
# 4: sys:x:3:3:sys:/dev:/usr/sbin/nologin
function e1() {
	local line_number=0;
	grep -v "^#" /etc/passwd | while read line
	do
		echo $line_number:" "$line
		((line_number++))
	done
}


# Exercise 2:
# Write a shell script that asks the user for the number of lines they would like to display from the
# /etc/passwd file and display those lines.
# Example output:
# How many lines of /etc/passwd would you like to see? 3
# root:x:0:0:root:/root:/bin/bash
# daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
# bin:x:2:2:bin:/bin:/usr/sbin/nologin
function e2() {
	read -p "How many lines of /etc/passwd would you like to see? " number_of_lines_user_see
	local line_number=0;
	grep -v "^#" /etc/passwd | while read line
	do
		if [ $number_of_lines_user_see -le $line_number ]
			then
				break
		fi
		echo $line_number:" "$line
		((line_number++))
	done
}


# Exercise 3:
# Write a shell script that that allows a user to select an action from the menu. The actions are to
# show the disk usage, show the uptime on the system, and show the users that are logged into
# the system. Tell the user to enter q​to quit. Display "Goodbye!" just before the script exits.
# If the user enters anything other than 1​, 2​, 3​, or q​, tell them that it is an "Invalid option."
# You can show the disk usage by using the df​command. To show the uptime, use the uptime
# command. To show the users logged into the system, use the who​command. Print a blank
# line after the output of each command.
# Example output:
# 1. Show disk usage.
# 2. Show system uptime.
# 3. Show the users logged into the system.
# What would you like to do? (Enter q to quit.) 2
# 14:59:08 up 3 days, 7:36, 7 users, load average: 0.13, 0.22, 0.33
# 1. Show disk usage.
# 2. Show system uptime.
# 3. Show the users logged into the system.
# What would you like to do? (Enter q to quit.) 4
# Invalid option.
# 1. Show disk usage.
# 2. Show system uptime.
# 3. Show the users logged into the system.
# What would you like to do? (Enter q to quit.) q
# Goodbye!

function e3() {
	while true
	do
		echo "1. Show disk usage."
		echo "2. Show system uptime.="
		echo "3. Show the users logged into the system."
		read -p "What would you like to do? (Enter q to quit.) " action
		case $action in
			1)
				df -h
				echo
				;;
			2)
				uptime
				echo
				;;
			3)
				whoami
				echo
				;;
			"q")
				echo "Goodbye!"
				break
				;;
			*)
				echo "Invalid option"
				;;
			esac
	done
}


function run() {
	if [ $# -ne 1 ]
	then
		echo "No exercise selected!"
		read -p "Please pass in the exercise number[1-${TOTAL_ALLOWED_EXERCISE}]: "  EXERCISE_NUMBER
	else
		EXERCISE_NUMBER=$1
    fi
	run_exercise $EXERCISE_NUMBER
}

function run_exercise() {
	if [ "$1" -le "$TOTAL_ALLOWED_EXERCISE" ]
		then 
			FUNCTION_NAME="e$1"
			$FUNCTION_NAME
    else
    	echo "Wrong exercise number passed: "$1
    fi
}
run $@