Question

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

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

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!

Answer 1

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 $@