# Print the current working directory
pwd

# List files and directories
ls

# Change directory
cd /path/to/directory

# Go to home directory
cd ~

# Go up one directory
cd ..

# Create a new directory
mkdir new_directory

# Create a new file
touch new_file.txt

# Remove a file
rm new_file.txt

# Remove a directory
rmdir new_directory

# Remove a directory and its contents
rm -r directory_name

# View the contents of a file
cat filename.txt

# View the contents of a file with pagination
less filename.txt

# View the first few lines of a file
head filename.txt

# View the last few lines of a file
tail filename.txt

# View file permissions and ownership
ls -l filename.txt

# Change file permissions (read, write, execute)
chmod 755 filename.txt

# Change file owner
sudo chown user:group filename.txt

# Redirect output to a file (overwrite)
echo "Hello World" > output.txt

# Append output to a file
echo "New Line" >> output.txt

# Redirect stderr to a file
ls non_existent_file 2> error.txt

# Redirect both stdout and stderr to the same file
ls valid_file non_existent_file &> output_and_error.txt

# Use a pipe to send the output of one command to another
cat filename.txt | grep "search_term"

# Chain multiple commands together
cat filename.txt | grep "search_term" | wc -l

# Declare a variable
my_variable="Hello World"

# Use the variable
echo $my_variable

# Assign the output of a command to a variable
file_count=$(ls | wc -l)
echo "Number of files: $file_count"

# For loop to print numbers from 1 to 5
for i in {1..5}; do
  echo $i
done

# While loop to count down from 5
count=5
while [ $count -gt 0 ]; do
  echo $count
  ((count--))
done

# Check if a file exists
if [ -f "filename.txt" ]; then
  echo "File exists"
else
  echo "File does not exist"
fi

# Check if a directory exists
if [ -d "directory_name" ]; then
  echo "Directory exists"
fi

# List all running processes
ps

# List all processes, including background jobs
ps aux

# Kill a process by PID
kill <pid>

# Run a command in the background
command &

# Find a file by name
find /path/to/search -name "filename.txt"

# Search for a string in a file
grep "search_term" filename.txt

# Search for a string in all files in a directory
grep -r "search_term" /path/to/directory

# Define a function
my_function() {
  echo "Hello from the function"
}

# Call the function
my_function

# Edit crontab (schedule tasks)
crontab -e

# Example cron job to run a script every day at 2am
0 2 * * * /path/to/script.sh

# List scheduled cron jobs
crontab -l

# Shell script that checks if a directory exists and lists its contents
if [ -d "$1" ]; then
  echo "Directory exists. Listing contents:"
  ls "$1"
else
  echo "Directory does not exist."
fi

# Print the first column of a text file
awk '{print $1}' filename.txt

# Sum the values in the second column
awk '{sum += $2} END {print sum}' filename.txt

# Replace a string in a file
sed -i 's/old_string/new_string/g' filename.txt

# Delete lines matching a pattern
sed '/pattern/d' filename.txt

# Check connectivity to a remote host
ping google.com

# View all network connections
netstat -tuln

# Display IP address information
ifconfig

# Show routing table
route -n

# Create a tar archive
tar -cvf archive.tar /path/to/files

# Extract a tar archive
tar -xvf archive.tar

# Compress a file with gzip
gzip filename.txt

# Decompress a gzip file
gunzip filename.txt.gz