File Manipulation

Efficient file manipulation is essential for effective control over files and directories within the Linux environment. This section covers fundamental commands for efficient file management in the Shell environment.

touch

  • Description: Creates an empty file or updates the timestamp of an existing file.

  • Example usage:

    touch new_file.txt # Creates a new empty file named 'new_file.txt'
touch existing_file.txt # Updates the timestamp of 'existing_file.txt'

Note: The touch command is versatile; it creates a new file if it doesn’t exist or updates the timestamp of an existing file without altering its content. This command is useful for various file management tasks within the Linux system.

nano

  • Description: Opens the Nano text editor for creating or editing files within the terminal.

  • Example usage:

    nano new_file.txt # Opens or creates a file named 'new_file.txt' for editing

Note: Nano text editor opens with a blank screen. Start typing your content. To save the file:

  • Press Ctrl + O (Write Out) to save the file.
  • Press Enter to confirm the filename.
  • Press Ctrl + X to exit Nano.

cat

  • Description: Displays the content of a file or concatenates files and displays the output.

  • Example usage:

    cat filename.txt # Displays the content of 'filename.txt'
cat file1.txt file2.txt # Concatenates 'file1.txt' and 'file2.txt' and displays the output

Note: The cat command can be used to display the content of a single file or concatenate multiple files. This command is commonly used for file content analysis and manipulation.

echo

  • Description: Prints text or variables as output to the terminal.

  • Example usage:

    echo "Hello, World!" # Prints "Hello, World!" to the terminal
echo $USER # Displays the current user's username
echo $HOME # Prints the path to the user's home directory
echo $PATH # Shows the directories where executable files are located.

export MY_VAR="Hello, Linux!" # Sets a custom variable MY_VAR
echo $MY_VAR # Prints the content of MY_VAR

Note: The echo command in Linux is like the “print” function in programming languages. It is a fundamental command often used for displaying messages, variables, or strings within shell scripts or for general output in the command line.

> (write)

  • Description: Redirects command output and writes it to a file, creating a new file or overwriting an existing one.

  • Example usage:

    cat file1.txt file2.txt > file3.txt
echo "Hello, World!" > output.txt # Writes "Hello, World!" to 'output.txt'

< (read)

  • Description: Redirects input from a file to a command. It provides the command with the content of the file as input.

  • Example usage:

      cat < input.txt # Provides 'cat' command with 'input.txt' content as input

Note: In this example, the < symbol for input redirection can be omitted. However, it becomes crucial in redirecting files within bash scripting (which you’ll explore in the next session). Here’s an example that you might not be able to execute now, but it’s worth trying later when you learn bash scripting:

  while read line; do
      echo "Processing line: $line"
      # Perform operations with each line of input
  done < input_data.txt  # Explicit input redirection using '<'

cp

  • Description: Copies files or directories from one location to another.

  • Example usage:

    cp file1.txt /destination/directory # Copies 'file1.txt' to '/destination/directory'
cp -r directory1 directory2 # Copies 'directory1' and its content to 'directory2'

mv

  • Description: Moves or renames files or directories.

  • Example usage:

    mv file1.txt newfile.txt # Renames 'file1.txt' to 'newfile.txt'
mv file1.txt /destination/directory # Moves 'file1.txt' to '/destination/directory'

rm

  • Description: Removes (deletes) files or directories.

  • Example usage:

      rm file1.txt # Deletes 'file1.txt'
  rm -r directory1 # Deletes 'directory1' and its content

  • Description: Displays the beginning lines of a file.

  • Example usage:

      head filename.txt # Displays the first ten lines of 'filename.txt'
  head -n 5 filename.txt # Displays the first five lines of 'filename.txt'

tail

  • Description: Displays the ending lines of a file.

  • Example usage:

    tail filename.txt # Displays the last ten lines of 'filename.txt'
tail -n 5 filename.txt # Displays the last five lines of 'filename.txt'

less

  • Description: Allows scrolling through the contents of a file.

  • Example usage:

    less book.txt # Opens 'book.txt' for browsing its content
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Note: more and less are both used to view file contents in a terminal. However, less is an improved version of more.