Linux shell operations and Bash automation

This case documents foundational operator work on a Linux lab host. We validated shell identity, navigated the filesystem, compared available login shells, and delivered Bash scripts for interactive input, iteration, conditional authorization, and keyword search across system logs. The same primitives appear in every later Linux engagement when we land a reverse shell or SSH session.

Sessions open in the user home directory. We printed the working directory, changed into Desktop, listed entries, and read a sample file. Pattern search with grep is the same technique we later apply to dictionaries, configs, and log corpora.

We recorded $SHELL, listed valid login shells, and entered zsh. Bash remains the default on most distributions and is our scripting target. Fish provides syntax highlighting and spell correction out of the box. Zsh combines advanced completion with heavy customization. Permanent default changes use chsh -s.

Automation starts as a file of commands. We authored first_script.sh with #!/bin/bash, prompted for a name, and echoed a welcome line. Execution requires chmod +x and an explicit ./ path so the shell does not search PATH for a local file.

#!/bin/bash
echo "Hey, what's your name?"
read name
echo "Welcome, $name"

Loops encode repetitive operator tasks. Conditionals encode policy. We validated both patterns before composing them into a multi-field authentication script.

#!/bin/bash
for i in {1..10};
do
  echo $i
done

#!/bin/bash

# Gate disclosure on an authorized identity.
echo "Please enter your name first:"
read name

if [ "$name" = "Stewart" ]; then
  echo "Welcome Stewart! Here is the secret: LAB_Script"
else
  echo "Sorry! You are not authorized to access the secret."
fi

We implemented a locker gate that prompts for three fields and evaluates them with a compound condition. Failed PIN attempts are denied without disclosing which field failed — appropriate for an access-control demo, insufficient for production auth (no rate limiting, no hashing).

#!/bin/bash

username=""
companyname=""
pin=""

for i in {1..3}; do
  if [ "$i" -eq 1 ]; then
    echo "Enter your Username:"
    read username
  elif [ "$i" -eq 2 ]; then
    echo "Enter your Company name:"
    read companyname
  else
    echo "Enter your PIN:"
    read pin
  fi
done

if [ "$username" = "John" ] && [ "$companyname" = "Savvy" ] && [ "$pin" = "7385" ]; then
  echo "Authentication Successful. You can now access your locker, John."
else
  echo "Authentication Denied!!"
fi

A search script in /home/user required the keyword and target directory before scanning *.log files. Full visibility under /var/log required root. We escalated with sudo su, filled the empty parameters, and confirmed the match in authentication.log.