Bash Scripting Questions

#!/bin/bash

# Prompt the user to enter the first number
echo "Enter the first number:"
read num1

# Prompt the user to enter the second number
echo "Enter the second number:"
read num2

# Calculate the sum
sum=$((num1 + num2))

# Print the sum
echo "The sum of $num1 and $num2 is: $sum"

#!/bin/bash

backup_dir="backup"

# Check if the directory exists
if [ ! -d "$backup_dir" ];
then
    # If it doesn't exist, create it
    mkdir "$backup_dir"
    echo "Backup directory created."
else
    echo "Backup directory already exists."
fi

#!/bin/bash
echo "Finding files larger than 1MB in the current directory:"
find . -type f -size +1M -exec ls -lh {} \;

#!/bin/bash
echo "Enter the directory name:"
read directory

# Check if the directory exists
if [ -d "$directory" ]; 
then
    # Count the number of files in the directory and print the count
    num_files=$(find "$directory" -maxdepth 1 -type f | wc -l)
    echo "Number of files in '$directory': $num_files"
else
    echo "Directory '$directory' does not exist."
fi

#!/bin/bash

# Prompt the user to enter a string
echo "Enter a string:"
read input_string

# Count the number of words in the string
word_count=$(echo "$input_string" | wc -w)

# Print the number of words
echo "Number of words in the string: $word_count"

#!/bin/bash

# Prompt the user to enter a filename
echo "Enter the filename:"
read filename

# Check if the file exists
if [ ! -f "$filename" ]; 
then
    echo "File '$filename' not found."
    exit 1
fi

# Prompt the user to enter a word to search for
echo "Enter the word to count:"
read word

# Count the number of occurrences of the word in the file
word_count=$(grep -o "\<$word\>" "$filename" | wc -l)

# Print the number of occurrences
echo "Number of occurrences of '$word' in '$filename': $word_count"

#!/bin/bash

echo "Symbolic links in the / directory:"

find / -type l -print

#!/bin/bash

# Prompt the user to enter a directory name
echo "Enter the directory name:"
read dir

# Check if the directory exists
if [ ! -d "$dir" ]; 
then
    echo "Directory '$dir' not found."
    exit 1
fi
# Calculate the total size of all files in the directory
total_size=$(du -sh "$dir" | cut -f1)
# Print the total size
echo "Total size of all files in '$dir': $total_size"

#!/bin/bash

# Prompt the user to enter the first filename
echo "Enter the first filename:"
read filename1
# Prompt the user to enter the second filename
echo "Enter the second filename:"
read filename2

# Check if the files exist
if [ ! -f "$filename1" ] || [ ! -f "$filename2" ]; 
then
    echo "One or both files do not exist."
    exit 1
fi
# Compare the contents of the files
if cmp -s "$filename1" "$filename2"; 
then
    echo "Files are identical."
else
    echo "Files are different."
fi

#!/bin/bash

# Prompt the user to enter a filename
echo "Enter the filename:"
read filename

# Check if the file exists
if [ ! -f "$filename" ]; 
then
    echo "File '$filename' not found."
    exit 1
fi

# Get the file's permissions in symbolic notation
permissions=$(stat -c "%A" "$filename")
# Print the file's permissions
echo "Permissions of '$filename': $permissions"

#!/bin/bash

# Check if there are no arguments
if [ $# -eq 0 ]; 
then
    echo "Usage: $0 <filename1> <filename2> ..."
    exit 1
fi

# Name of the concatenated file
output_file="concatenated_file.txt"

# Concatenate the contents of all files into the output file
cat "$@" > "$output_file"

echo "Contents of the following files have been concatenated into '$output_file':"
echo "$@"

#!/bin/bash

# Prompt the user to enter a directory name
echo "Enter the directory name:"
read directory_name

# Check if the directory already exists
if [ -d "$directory_name" ]; 
then
    echo "Directory '$directory_name' already exists."
else
    # Create the directory
    mkdir "$directory_name"
    echo "Directory '$directory_name' created."

    # Create subdirectories for each day of the week
    for day in Monday Tuesday Wednesday Thursday Friday; 
    do
        mkdir "$directory_name/$day"
        echo "Subdirectory '$day' created."
    done
fi

#!/bin/bash
# Prompt the user to enter a number
echo "Enter a number:"
read number

# Check if the number is greater than zero
if ((number > 0)); 
then
    echo "Positive"
# Check if the number is less than zero
elif ((number < 0)); 
then
    echo "Negative"
# If neither of the above conditions is met, the number is zero
else
    echo "Zero"
fi

#!/bin/bash

# Prompt the user to enter a filename
echo "Enter the filename:"
read filename

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

# Check if the file is executable
if [ -x "$filename" ]; 
then
    echo "File '$filename' is executable."
else
    echo "File '$filename' is not executable."
fi

#!/bin/bash
# Prompt the user to enter their age
echo "Enter your age:"
read age

# Check if the age is greater than or equal to 18
if [ "$age" -ge 18 ]; 
then
    echo "You are an adult."
else
    echo "You are a minor."
fi

#!/bin/bash
# Prompt the user to enter a username
echo "Enter the username:"
read username

# Check if the user exists
if id "$username" &>/dev/null; 
then
    echo "User '$username' exists."
else
    echo "User '$username' does not exist."
fi

#!/bin/bash

# Check if the SSH service is running
if systemctl is-active --quiet sshd; 
then
    echo "SSH service is running."
else
    # Start the SSH service
    sudo systemctl start sshd
    echo "SSH service started."
fi

#!/bin/bash

# Check if nginx is installed
if rpm -q nginx &>/dev/null; then
    echo "Nginx is installed."
else
    # Install nginx
    sudo dnf install nginx -y
    echo "Nginx installed successfully."
fi

#!/bin/bash

# Set the threshold for disk usage
threshold=90
# Get the current disk usage of the root filesystem
disk_usage=$(df -h / | awk 'NR==2 {print $5}' | cut -d'%' -f1)

# Check if the disk usage exceeds the threshold
if [ "$disk_usage" -gt "$threshold" ]; 
then
    echo "Disk usage high"
else
    echo "Disk usage normal"
fi

#!/bin/bash

# Check if the user "admin" exists
if id "admin" &>/dev/null; 
then
    echo "User 'admin' exists."
else
    # Create the user "admin"
    sudo useradd -m admin
    echo "User 'admin' created successfully."
fi

#!/bin/bash

# Check if the current user has sudo access
if sudo -n true 2>/dev/null; 
then
    echo "User has sudo access."
else
    echo "User does not have sudo access."
fi

#!/bin/bash

# Define the threshold for the load average
threshold=2.0

# Get the current 1-minute load average
load_average=$(uptime | awk -F 'load average: ' '{print $2}' | cut -d, -f1)

# Check if the load average exceeds the threshold
if [ $(echo "$load_average > $threshold" | bc) -eq 1 ]; 
then
    echo "Warning: System load average ($load_average) exceeds threshold ($threshold)."
else
    echo "System load normal."
fi

#!/bin/bash

# Define the threshold for available disk space (in GB)
threshold_gb=1
# Get available disk space in /home directory (in GB)
available_space_gb=$(df -BG /home | awk 'NR==2 {print $4}' | sed 's/G//')

# Check if available space is less than the threshold
if [ "$available_space_gb" -lt "$threshold_gb" ]; 
then
    echo "Warning: Available disk space in /home is less than 1GB."
else
    echo "Disk space is sufficient."
fi

#!/bin/bash

# Check if the user "john" is logged in
if who | grep -q "\<john\>"; 
then
    echo "User is logged in."
else
    echo "User is not logged in."
fi

#!/bin/bash

# Get the system uptime in seconds
uptime_seconds=$(cut -d' ' -f1 /proc/uptime)

# Calculate the uptime in hours
uptime_hours=$(bc <<< "scale=2; $uptime_seconds / 3600")

# Check if the uptime is less than 1 hour
if (( $(bc <<< "$uptime_hours < 1") )); 
then
    echo "System recently started"
else
    echo "System has been running for a while"
fi

#!/bin/bash

# Define the network interface to check
interface="enp0s3"

# Check if the interface is up
if ip link show "$interface" &> /dev/null; 
then
    echo "Interface is up"
else
    echo "Interface is down"
fi

#!/bin/bash

# Get the current user's home directory
home_directory=$(eval echo "~")

# Check if the home directory is located in /home
if [[ "$home_directory" == "/home"* ]]; 
then
    echo "Home directory standard"
else
    echo "Home directory non-standard"
fi