Scenario There is a customer who came to you with a problem to have a custom linux command for his operations. Your task is to understand the problem and create a linux command via bash script as per the instructions. Command name - internsctl Command version - v0.1.0 Section A

1. I want a manual page of command so that I can see the full documentation of the command. For example if you execute the command man ls as output we get the doc and usage guidelines. Similarly if I execute man internsctl I want to see the manual of my command.

Output: sudo cp internsctl.1 /usr/share/man/man1/ sudo mandb

2. Each linux command has an option --help which helps the end user to understand the use cases via examples. Similarly if I execute internsctl --help it should provide me the necessary help

Output:

#!/bin/bash

Define the version

VERSION="v0.1.0"

Function to display help message

display_help() { echo "Usage: internsctl [OPTIONS] DIRECTORY" echo "Custom Linux command for operations." echo echo "Options:" echo " -h, --help Display this help message." echo " -v, --version Display the version of internsctl." echo " -a, --action DIR Perform a custom action on the specified directory." echo echo "Examples:" echo " internsctl -a /path/to/directory" echo " internsctl --version" echo }

Function to display version

display_version() { echo "internsctl $VERSION" }

Parse command line options

while [[ $# -gt 0 ]]; do case $1 in -h|--help) display_help exit 0 ;; -v|--version) display_version exit 0 ;; -a|--action) if [ -n "$2" ]; then DIRECTORY=$2 # Add your custom action here echo "Performing custom action on directory: $DIRECTORY" shift 2 else echo "Error: -a|--action option requires a directory argument." exit 1 fi ;; *) echo "Error: Unknown option '$1'. Use --help for usage information." exit 1 ;; esac done

Check if the DIRECTORY argument is provided

if [ -z "$DIRECTORY" ]; then echo "Error: DIRECTORY argument is required. Use --help for usage information." exit 1 fi

3. I want to see version of my command by executing internsctl –version

Output : #!/bin/bash

Define the version

VERSION="v0.1.0"

Function to display help message

display_help() { echo "Usage: internsctl [OPTIONS] DIRECTORY" echo "Custom Linux command for operations." echo echo "Options:" echo " -h, --help Display this help message." echo " -v, --version Display the version of internsctl." echo " -a, --action DIR Perform a custom action on the specified directory." echo echo "Examples:" echo " internsctl -a /path/to/directory" echo " internsctl --version" echo }

Function to display version

display_version() { echo "internsctl $VERSION" }

Parse command line options

while [[ $# -gt 0 ]]; do case $1 in -h|--help) display_help exit 0 ;; -v|--version) display_version exit 0 ;; -a|--action) if [ -n "$2" ]; then DIRECTORY=$2 # Add your custom action here echo "Performing custom action on directory: $DIRECTORY" shift 2 else echo "Error: -a|--action option requires a directory argument." exit 1 fi ;; *) echo "Error: Unknown option '$1'. Use --help for usage information." exit 1 ;; esac done

Check if the DIRECTORY argument is provided

if [ -z "$DIRECTORY" ]; then echo "Error: DIRECTORY argument is required. Use --help for usage information." exit 1 fi Now, when you execute internsctl --version, it will display the version of the internsctl command.

Section B I want to execute the following command for - Part1 | Level Easy I want to get cpu information of my server through the following command: $ internsctl cpu getinfo Expected Output - I want similar output as we get from lscpu command

I want to get memory information of my server through the following command: $ internsctl memory getinfo Expected Output I want similar output as we get from free command

OUTPUT : #!/bin/bash

Define the version

VERSION="v0.1.0"

Function to display help message

display_help() { echo "Usage: internsctl [OPTIONS] COMMAND" echo "Custom Linux command for operations." echo echo "Options:" echo " -h, --help Display this help message." echo " -v, --version Display the version of internsctl." echo echo "Commands:" echo " cpu getinfo Get CPU information (similar to lscpu)." echo " memory getinfo Get memory information (similar to free)." echo echo "Examples:" echo " internsctl cpu getinfo" echo " internsctl memory getinfo" echo " internsctl --version" echo }

Function to display version

display_version() { echo "internsctl $VERSION" }

Function to get CPU information

get_cpu_info() { lscpu }

Function to get memory information

get_memory_info() { free }

Parse command line options

while [[ $# -gt 0 ]]; do case $1 in -h|--help) display_help exit 0 ;; -v|--version) display_version exit 0 ;; cpu) if [ "$2" == "getinfo" ]; then get_cpu_info exit 0 else echo "Error: Invalid usage of 'cpu' command. Use 'internsctl cpu getinfo'." exit 1 fi ;; memory) if [ "$2" == "getinfo" ]; then get_memory_info exit 0 else echo "Error: Invalid usage of 'memory' command. Use 'internsctl memory getinfo'." exit 1 fi ;; *) echo "Error: Unknown option or command '$1'. Use --help for usage information." exit 1 ;; esac done

If no command is provided, display help

echo "Error: No command provided. Use --help for usage information." exit 1 This script introduces two new commands: cpu getinfo and memory getinfo. When you run internsctl cpu getinfo, it will display CPU information similar to lscpu. Similarly, running internsctl memory getinfo will show memory information similar to free. Adjust the script based on your specific needs and further customize the output format if necessary.

Part2 | Level Intermediate I want to create a new user on my server through the following command: $ internsctl user create Note - above command should create user who can login to linux system and access his home directory

I want to list all the regular users present on my server through the following command: $ internsctl user list

If want to list all the users with sudo permissions on my server through the following command: $ internsctl user list --sudo-only

OUTPUT #!/bin/bash

Define the version

VERSION="v0.1.0"

Function to display help message

display_help() { echo "Usage: internsctl [OPTIONS] COMMAND [ARGS]" echo "Custom Linux command for operations." echo echo "Options:" echo " -h, --help Display this help message." echo " -v, --version Display the version of internsctl." echo echo "Commands:" echo " user create Create a new user with login access and home directory." echo " user list List all regular users." echo " user list --sudo-only List users with sudo permissions." echo echo "Examples:" echo " internsctl user create john_doe" echo " internsctl user list" echo " internsctl user list --sudo-only" echo " internsctl --version" echo }

Function to display version

display_version() { echo "internsctl $VERSION" }

Function to create a new user

create_user() { if [ -n "$1" ]; then sudo useradd -m -s /bin/bash "$1" echo "User '$1' created successfully." else echo "Error: Missing username. Use 'internsctl user create '." exit 1 fi }

Function to list all regular users

list_users() { cut -d: -f1 /etc/passwd }

Function to list users with sudo permissions

list_sudo_users() { getent group sudo | cut -d: -f4 | tr ',' '\n' }

Parse command line options

while [[ $# -gt 0 ]]; do case $1 in -h|--help) display_help exit 0 ;; -v|--version) display_version exit 0 ;; user) shift case $1 in create) shift create_user "$1" exit 0 ;; list) shift if [ "$1" == "--sudo-only" ]; then list_sudo_users else list_users fi exit 0 ;; *) echo "Error: Invalid usage of 'user' command. Use 'internsctl user create ' or 'internsctl user list [--sudo-only]'." exit 1 ;; esac ;; *) echo "Error: Unknown option or command '$1'. Use --help for usage information." exit 1 ;; esac done

If no command is provided, display help

echo "Error: No command provided. Use --help for usage information." exit 1 This script now supports three commands related to user management:

internsctl user create - Create a new user with login access and a home directory. internsctl user list - List all regular users. internsctl user list --sudo-only - List users with sudo permissions.

Part3 | Advanced Level By executing below command I want to get some information about a file $ internsctl file getinfo Expected Output [make sure to have the output in following format only] xenonstack@xsd-034:$ internsctl file getinfo hello.txt File: hellot.txt Access: -rw-r--r-- Size(B): 5448 Owner: xenonstack Modify: 2020-10-07 20:34:44.616123431 +0530 In case I want only specific information then I must have a provision to use options $ internsctl file getinfo [options] --size, -s to print size --permissions, -p print file permissions --owner, o print file owner --last-modified, m Expected Output with options If I want to obtain the size of the specified file only, I should be able to use the following command: xenonstack@xsd-034:$ internsctl file getinfo --size hello.txt 5448 If I want to obtain the permissions of the specified file only, I should be able to use the following command: xenonstack@xsd-034:$ internsctl file getinfo --permissions hello.txt -rw-r--r-- If I want to obtain the owner of the specified file only, I should be able to use the following command: xenonstack@xsd-034:$ internsctl file getinfo --owner hello.txt xenonstack If I want to obtain the last modified time of the specified file only, I should be able to use the following command: xenonstack@xsd-034:~$ internsctl file getinfo --last-modified hello.txt 2020-10-07 20:34:44.616123431 +0530 OUTPUT: #!/bin/bash

Define the version

VERSION="v0.1.0"

Function to display help message

display_help() { echo "Usage: internsctl [OPTIONS] COMMAND [ARGS]" echo "Custom Linux command for operations." echo echo "Options:" echo " -h, --help Display this help message." echo " -v, --version Display the version of internsctl." echo echo "Commands:" echo " file getinfo Get information about a file." echo " Options:" echo " --size, -s Print file size." echo " --permissions, -p Print file permissions." echo " --owner, -o Print file owner." echo " --last-modified, -m Print last modified time." echo echo "Examples:" echo " internsctl file getinfo hello.txt" echo " internsctl file getinfo --size hello.txt" echo " internsctl file getinfo --permissions hello.txt" echo " internsctl file getinfo --owner hello.txt" echo " internsctl file getinfo --last-modified hello.txt" echo " internsctl --version" echo }

Function to display version

display_version() { echo "internsctl $VERSION" }

Function to get information about a file

get_file_info() { FILENAME=$1

# Check if the file exists
if [ ! -e "$FILENAME" ]; then
    echo "Error: File '$FILENAME' does not exist."
    exit 1
fi

# Default output
OUTPUT="File: $FILENAME"

# Check options
while [[ $# -gt 0 ]]; do
    case $1 in
        --size|-s)
            OUTPUT+="\nSize(B): $(stat -c %s "$FILENAME")"
            ;;
        --permissions|-p)
            OUTPUT+="\nAccess: $(stat -c %A "$FILENAME")"
            ;;
        --owner|-o)
            OUTPUT+="\nOwner: $(stat -c %U "$FILENAME")"
            ;;
        --last-modified|-m)
            OUTPUT+="\nModify: $(stat -c %y "$FILENAME")"
            ;;
        *)
            # Unknown option
            echo "Error: Unknown option '$1'. Use --help for usage information."
            exit 1
            ;;
    esac
    shift
done

echo -e "$OUTPUT"

}

Parse command line options

while [[ $# -gt 0 ]]; do case $1 in -h|--help) display_help exit 0 ;; -v|--version) display_version exit 0 ;; file) shift case $1 in getinfo) shift get_file_info "$1" "${@:2}" exit 0 ;; *) echo "Error: Invalid usage of 'file' command. Use 'internsctl file getinfo [options]'." exit 1 ;; esac ;; *) echo "Error: Unknown option or command '$1'. Use --help for usage information." exit 1 ;; esac done

If no command is provided, display help

echo "Error: No command provided. Use --help for usage information." exit 1 This script now supports the file getinfo command with various options (--size, --permissions, --owner, --last-modified)