w07-commands.sh

#!/bin/bash
# shellcheck disable=SC2002
# shellcheck disable=SC2020
# shellcheck disable=SC2086
# shellcheck disable=SC2317
# shellcheck disable=SC1073
# shellcheck disable=SC1009

# shellcheck disable=SC1072

## Common BASH shell environment files and the order in which they are typically
## executed are as follows:
# /etc/profile
# /etc/profile.d/*
# /etc/bashrc
# ~/.bashrc
# ~/.bash_profile
# ~/.bash_login
# ~/.profile

## WEEK 07
## =============================================================================
## PROJECT 7-1
## Objective: Perform shell redirection.
## Description: In this hands-on project, you use the shell to redirect the
## stdout and stderr to a file and take stdin from a file.
touch sample1 sample2                    # Create two empty files: sample1 and sample2
ls -F                                    # List files in the directory with special characters to indicate type
ls -l sample1 sample2 sample3            # List detailed info for sample1, sample2, and non-existent sample3 (stderr expected)
ls -l sample1 sample2 sample3 > file     # Redirect stdout to 'file'; stderr (if any) still appears on screen
cat file                                 # Display contents of 'file' (only stdout from previous command)
ls -l sample1 sample2 sample3 2> file    # Redirect stderr to 'file'; stdout (if any) appears on screen
cat file                                 # Display contents of 'file' (only stderr from previous command)
ls -l sample1 sample2 sample3 > file 2>file2  # Redirect stdout to 'file' and stderr to 'file2'
cat file                                 			# Show stdout from previous ls command
cat file2                                			# Show stderr from previous ls command
ls -l sample1 sample2 sample3 > file 2>&1   	# Redirect both stdout and stderr to 'file'
cat file                                 			# Show combined stdout and stderr from previous command
ls -l sample1 sample2 sample3 >&2 2>file2   	# Redirect both stdout and stderr to stderr, then redirect stderr to 'file2'
cat file2                                # Show captured stderr from previous command
date > file                              # Overwrite 'file' with current date
cat file                                 # Show contents of 'file' (should be the current date)
date >> file                             # Append current date to 'file'
cat file                                 # Show both dates; first from overwrite, second from append
tr o O /etc/hosts                        # Incorrect usage: tr doesn't take filenames as arguments (stderr expected)
tr o O </etc/hosts                       # Correct: replaces all 'o' with 'O' from /etc/hosts and outputs result
tr o O <<EOF                             # Start here-doc input redirection to tr (until EOF is entered)
oranges
Toronto
Donkey Kong
EOF

## =============================================================================
## PROJECT 7-2
## Objective: Perform shell piping.
## Description: In this hands-on project, you redirect stdout and stdin using 
## pipe metacharacters.
cat /etc/services                               # Display the contents of /etc/services
cat /etc/services | less                        # View the contents page-by-page using less via a pipe
cat /etc/services | grep NFS                    # Filter lines containing "NFS"; grep reads from stdin
cat /etc/services | grep NFS | tr F f           # Replace uppercase 'F' with lowercase 'f' in the grep output
cat /etc/services | grep NFS | tr F f | sort -r # Sort the modified lines in reverse order
cat /etc/services | grep NFS | tr F f | sort -r | tee file      # Save output to 'file' and display on screen
cat file                                        # Show contents of 'file'; matches previous output
cat /etc/services | grep NFS | tr F f | sort -r | tee file | wc -l  # Count number of lines; saves intermediate output to 'file'
cat file                                        # Show contents of 'file' to verify tee output
cat /etc/services | grep NFS | tr F f | sort -r | sed /udp/d | sed /tcp/s/mount/MOUNT/g  # Remove lines with 'udp', replace 'mount' with 'MOUNT' in 'tcp' lines
cat /etc/hosts                                  # Display contents of /etc/hosts
cat /etc/hosts | awk '/localhost/ {print $1, $3}'  # Print first and third fields of lines containing 'localhost'

## =============================================================================
## PROJECT 7-3
## Objective: Create and manage variables.
## Description: In this hands-on project, you create and use an alias, as well
## as view and change existing shell variables. In addition, you export
## user-defined variables and load variables automatically upon shell startup.
# shellcheck disable=SC2002

set | less                              # View all shell variables; scroll with arrow keys, quit with 'q'
env | less                              # View exported environment variables; usually fewer than `set` because it only shows exported ones
PS1="Hello There:"                      # Temporarily change the shell prompt to "Hello There:"
echo $PS1                               # Display current value of the PS1 variable
exit                                    # Log out of the shell

# After re-login:
# The prompt reverts because the PS1 change wasn't persisted
vi .bash_profile                        # Open user's shell profile to persist settings
# Add the following to the bottom of .bash_profile:
# echo -e "Would you like a hello prompt? (y/n) -->\c"
# read ANSWER
# if [ $ANSWER = "y" -o $ANSWER = "Y" ]
# then
# PS1="Hello There: "
# fi
# This script prompts user at login, and sets the prompt to "Hello There: " if they answer 'y' or 'Y'

exit                                    # Log out to test the new .bash_profile behavior
# Log back in and enter 'y' at the prompt — prompt changes to "Hello There:"

exit                                    # Log out again
# Log in again and enter 'n' at the prompt — default prompt appears

MYVAR="My sample variable"              # Create a shell variable called MYVAR
echo $MYVAR                             # Display value of MYVAR
set | grep MYVAR                        # MYVAR appears because it's set in the shell
env | grep MYVAR                        # MYVAR does not appear — not exported yet
export MYVAR                            # Export MYVAR to make it available to subshells
env | grep MYVAR                        # MYVAR now appears in environment list
exit                                    # Log out again

# After re-login:
echo $MYVAR                             # MYVAR is not defined — because it wasn't set in .bash_profile
vi .bash_profile                        # Edit profile to make MYVAR persistent
# Add this line at the bottom of .bash_profile:
# export MYVAR="My sample variable"
exit                                    # Log out again

# After re-login:
echo $MYVAR                             # MYVAR is now available automatically
alias                                   # Show defined aliases
alias asample="cd /etc ; cat hosts ; cd ~ ; ls -F"  # Define alias: go to /etc, display hosts file, return home, list files with markers
asample # Run the alias; output from each command is displayed in sequence
				# To persist this alias across sessions, add it to ~/.bashrc
exit                                    # Logout of the shell


## =============================================================================
## PROJECT 7-4
## Objective: Create a basic shell script.
## Description: In this hands-on project, you create a basic shell script and
## execute it on the system.

vi myscript                             # Open a new file called 'myscript' in the vi editor

# Inside vi, enter the following lines:
# ------------------------------------
# #!/bin/bash
# echo -e "This is a sample shell script. \t It displays mounted filesystems: \a"
# df -hT
# ------------------------------------
# Save and quit vi with :wq

ls -l myscript                          # List file details and permissions for 'myscript'
bash myscript                           # Run the script using the bash interpreter directly

# \t = horizontal tab, \a = alert/bell (may make a sound or flash)

./myscript                              # Try to execute script directly (will likely fail due to missing execute permission)

chmod u+x myscript                      # Add execute permission for the file owner
./myscript                              # Now run the script directly after setting execute permission

exit                                    # Log out of the shell


## =============================================================================
## PROJECT 7-5
## Objective: Create system administration shell scripts.
## Description: In this hands-on project, you create a shell script that uses 
## decision and loop constructs to analyze user input.

vi diskconfig.sh                          # Open a new shell script file named diskconfig.sh in the vi editor

# Inside vi, enter the following script:
# --------------------------------------
# #!/bin/bash                                               # Use the Bash shell to interpret the script
# # This script creates a report of our disk configuration
# FILENAME=$(hostname)                                      # Assign the system's hostname to the variable FILENAME
# echo "Disk report saved to $FILENAME.report"              # Print message showing the name of the output report file
# echo -e "\n LVM Configuration: \n\n" >> $FILENAME.report  # Write LVM section header into the report file
# lvscan >> $FILENAME.report                                # Append output of logical volume scan to the report
# echo -e "\n\n Partition Configuration: \n\n" >> $FILENAME.report  # Write partition section header into the report
# fdisk -l | head -17 >> $FILENAME.report                           # Append first 17 lines of partition info to the report
# echo -e "\n\n Mounted Filesystems: \n\n" >> $FILENAME.report      # Write mounted filesystems header into the report
# df -hT | grep -v tmp >> $FILENAME.report                          # Append mounted filesystems (excluding tmpfs) to the report
# --------------------------------------
# Save and quit vi with :wq


chmod u+x diskconfig.sh                   # Grant execute permission to the script
./diskconfig.sh                           # Run the disk configuration script

less "$(hostname).report"                # View the generated report with less

vi dirbackup.sh                           # Open a new shell script file named dirbackup.sh

# Inside vi, enter the following first version:
# --------------------------------------
# #!/bin/bash                                              	   # Use the Bash shell to interpret the script
# # This script backs up a directory of your choice	   
# if [ $# -ne 1 ]; then                                    	   # Check if exactly one argument (directory) was passed
#   echo "Usage is $0 <directory to back up>"              	   # Print usage message with script name if not
#   exit 255                                               	   # Exit with status code 255 indicating error
# fi	   
# echo "Performing backup....."                            	   # Inform user that backup is starting
# sleep 3                                                  	   # Pause for 3 seconds for dramatic effect
# tar -zcvf ~/backupfile.tar.gz $1                         	   # Create compressed archive of the directory passed as argument
# echo "Backup completed successfully to ~/backupfile.tar.gz"  # Inform user that the backup has completed
# --------------------------------------
# Save and quit vi with :wq

chmod u+x dirbackup.sh                    # Make script executable
./dirbackup.sh                            # Run without argument to see the error
./dirbackup.sh /etc/samba                 # Run with argument to back up /etc/samba

ls -F                                     # List files in current directory to check for backup

vi dirbackup.sh                           # Edit the script for input-based backup

# Modify the script to:
# --------------------------------------
# #!/bin/bash                                                      # Use the Bash shell to interpret the script
# # This script backs up a directory of your choice
# echo -e "What directory do you want to back up?-->\c"           # Prompt user to input a directory path (with no newline)
# read ANS                                                        # Read the user input into the variable ANS
# echo "Performing backup....."                                   # Inform user that backup is starting
# sleep 3                                                         # Pause for 3 seconds for user clarity
# tar -zcvf ~/backupfile.tar.gz $ANS                              # Create compressed archive of the specified directory
# echo "Backup completed successfully to ~/backupfile.tar.gz"     # Inform user that the backup has completed
# --------------------------------------
# Save and quit vi with :wq

./dirbackup.sh                            # Run and input e.g. /etc/httpd when prompted
vi dirbackup.sh                           # Modify the script to include directory and date in filename

# Modify the script to:
# --------------------------------------
# #!/bin/bash                                                        # Use the Bash shell to interpret the script
# # This script backs up a directory of your choice
# echo -e "What directory do you want to back up?-->\c"             # Prompt user for directory path (no newline after prompt)
# read ANS                                                          # Read user input into the variable ANS
# echo "Performing backup....."                                     # Notify the user that the backup is starting
# sleep 3                                                           # Pause for 3 seconds for visibility
# FILE=$(echo $ANS | sed 's#/#-#g')                                 # Replace all forward slashes in directory path with dashes for filename
# DATE=$(date +%F)                                                  # Store current date in YYYY-MM-DD format
# tar -zcvf ~/backup-$FILE-$DATE.tar.gz $ANS                        # Create a gzipped tarball named with sanitized path and current date
# echo "Backup performed to ~/backup-$FILE-$DATE.tar.gz"           # Notify the user of successful backup and its location
# --------------------------------------
# Save and quit vi with :wq

./dirbackup.sh                            # Run and input e.g. /etc/httpd to create a timestamped backup
vi familydatabase.sh                      # Open a new shell script file named familydatabase.sh

# Enter the following:
# --------------------------------------
# #!/bin/bash                                                        # Use the Bash shell to interpret the script
# while true; do                                                     # Start an infinite loop
#   clear                                                            # Clear the screen before each iteration
#   echo -e "What would you like to do?                             # Display the menu options
# Add an entry (a)
# Search an entry (s)
# Quit (q)
# Enter your choice (a/s/q)-->\c"                                   # Prompt the user (no newline after prompt)
#   read ANSWER                                                     # Read user input into variable ANSWER
#   case $ANSWER in                                                 # Begin case block to handle user choice
#     a|A)                                                           # If user selects 'a' or 'A':
#       echo -e "Name of the family member --> \c"                  # Prompt for name
#       read NAME                                                   # Read name input
#       echo -e "Family member's relation to you -->\c"            # Prompt for relation
#       read RELATION                                               # Read relation input
#       echo -e "Family member's telephone number --> \c"          # Prompt for phone number
#       read PHONE                                                  # Read phone number input
#       echo -e "$NAME\t$RELATION\t$PHONE" >> database             # Append entered info to 'database' file, tab-separated
#       ;;                                                          # End of 'a' case block
#     s|S)                                                           # If user selects 's' or 'S':
#       echo -e "What word would you like to look for? --> \c"      # Prompt for search term
#       read WORD                                                   # Read search term input
#       grep "$WORD" database                                       # Search the 'database' file for the term
#       sleep 4                                                     # Pause for 4 seconds to view output
#       ;;                                                          # End of 's' case block
#     q|Q)                                                           # If user selects 'q' or 'Q':
#       exit                                                        # Exit the script
#       ;;                                                          # End of 'q' case block
#     *)                                                             # For any other input:
#       echo "You must enter either the letter a or s."             # Display usage error message
#       sleep 4                                                     # Pause for 4 seconds
#       ;;                                                          # End of default case block
#   esac                                                            # Close the case block
# done                                                              # Repeat the loop
# --------------------------------------
# Save and quit vi with :wq


chmod u+x familydatabase.sh               # Make the script executable
./familydatabase.sh                       # Run the family database script
# Test all options: a (add), s (search), x (invalid), q (quit)

exit                                      # Log out of the shell


## =============================================================================
## PROJECT 7-6
## Objective: Practice using Git.
## Description: In this hands-on project, you create a local Git repository for 
## the shell scripts that you created in Project 7-5 and explore Git version
## control.

mkdir /shellscripts                                  # Create a new directory called /shellscripts
mv diskconfig.sh dirbackup.sh familydatabase.sh /shellscripts     # Move the three scripts to the /shellscripts directory

git config --global user.email "[email protected]"     # Set the global Git email
git config --global user.name "root user"            # Set the global Git username
git config --global init.defaultBranch main          # Set the default Git branch name to main

cd /shellscripts                                     # Change to the /shellscripts directory
git init                                             # Initialize a new Git repository
ls -a                                                # List all files including hidden ones to confirm .git directory

git status                                           # Check current Git status (untracked files)
git add .                                            # Add all files to the Git staging area
git status                                           # Confirm that files are staged

git commit -m "First commit"                         # Create the first commit with a message

vi diskconfig.sh                                     # Open diskconfig.sh in vi editor
# (Add the following lines at the end of the file in vi)
echo -e "\n\n RAID Configuration: \n\n" >>$FILENAME.report    # Add RAID section heading to the report
mdadm --detail /dev/md0 >>$FILENAME.report                   # Add RAID details to the report

git status                                           # Check Git status to see if the file was modified
git add .                                            # Stage the modified file
git commit -m "Added RAID to diskconfig.sh"          # Commit the changes with a message

git log                                              # Show Git commit history
git reset --hard <commit>                            # Reset the repo to the specified previous commit
cat diskconfig.sh                                    # Display the contents of diskconfig.sh

cd                                                  # Return to the home directory
git clone /shellscripts                              # Clone the /shellscripts repository into the current directory
cd shellscripts                                      # Change into the cloned repository directory
ls -a                                                # List all files including .git to verify the clone

git branch                                           # Show current branch (should be main)
git checkout -b AddRAID                              # Create and switch to a new branch named AddRAID
git branch                                           # List branches to confirm AddRAID is the current branch

vi diskconfig.sh                                     # Open diskconfig.sh in vi editor
# (Add the following lines at the end of the file in vi)
echo -e "\n\n RAID Configuration: \n\n" >>$FILENAME.report    # Add RAID section heading again in branch
mdadm --detail /dev/md0 >>$FILENAME.report                   # Add RAID details again in branch

git add .                                            # Stage the modified file for commit in AddRAID branch
git commit -m "Added RAID to diskconfig.sh"          # Commit the change to the AddRAID branch

cat diskconfig.sh                                    # Show contents to confirm RAID lines are present
git checkout main                                    # Switch back to the main branch
cat diskconfig.sh                                    # Confirm the RAID lines are not present in main

git push origin AddRAID                              # Push AddRAID branch to the origin repository
cd /shellscripts                                     # Go to the original repository
git branch                                           # Verify that AddRAID exists and main is still the active branch

git show AddRAID                                     # Show the changes made in the AddRAID branch

git merge AddRAID                                    # Merge AddRAID into the current main branch
cat diskconfig.sh                                    # Confirm RAID lines are now in the main branch

cd ~/shellscripts                                    # Go back to the cloned repo in the home directory
git pull origin main                                 # Pull latest changes from the origin main branch

exit                                                 # Log out of the terminal


## =============================================================================
## PROJECT 7-7
## Objective: Set up and use the Z shell.
## Description: In this hands-on project, you install and explore the Z shell.
dnf -y install zsh                   # Install the Z shell non-interactively with auto-confirm
exit                                 # Log out of the root shell session
zsh                                  # Start the Z shell and enter the interactive configuration menu
vi .zshrc                            # Open Zsh config file in vi for manual editing; edit `setopt autocd` to `setopt autocd correct`, then save with :wq
source .zshrc                        # Reload .zshrc into the current shell session
grep NFS /etc/services >file1 >file2       # Only file2 gets the output; second redirection overrides the first
cat file1                                   # View contents of file1 (likely empty)
cat file2                                   # View contents of file2 (contains grep output)
grep NFS /etc/services >file1 | grep protocol >file2   # file1 gets output from grep NFS; file2 gets filtered result from the pipe
cat file1                                              # View file1 contents
cat file2                                              # View file2 contents
sort <file1 <file2 >file3              # Incorrect: only file2 is used due to conflicting redirections
cat file3                              # View file3 contents (likely only sorted file2)
grp NFS /etc/services                 # Typo triggers autocorrect; press y to fix to `grep`
date -                                # Press Tab to list valid options
date --universal                      # Show current date/time in UTC
pwd                                   # Show current working directory
Desktop                               # Change to Desktop directory using autocd
pwd                                   # Show new working directory (should be ~/Desktop)
exit                                  # Log out of Z shell session