Files Commands
1. ls - List directory contents
      ls - Lists all files and directories in the current directory.
      ls -l - Lists files and directories with detailed information      (permissions, owner, size, etc.).
2. cd - Change directory
      cd /home/user - Moves to the /home/user          directory.
      cd .. - Moves up one directory level.
3. pwd - Print working directory
      pwd   - Displays the current directory path.
4. cp - Copy files and directories
      file2.txt - Copies file1.txt to file2.txt.
      cp -r dir1/ dir2/ - Copies the directory dir1         to dir2.
5. mv - Move or rename files and directories
      mv file1.txt file2.txt - Renames file1.txt to file2.txt.
      mv file1.txt /home/user/ - Moves file1.txt to /home/user/.
6. rm - Remove files or directories
      rm file1.txt - Deletes file1.txt.
      rm -r dir1/ - Deletes the directory dir1       and its contents.
7. touch - Change file timestamps or create empty files
      touch newfile.txt - Creates an empty file named newfile.txt.
      touch file1.txt - Updates the timestamp of file1.txt if it already exists.
8. cat - Concatenate and display file content
      cat file1.txt - Displays the content of file1.txt.
      cat file1.txt file2.txt - Displays the content of file1.txt              followed by file2.txt.
9. chmod - Change file modes or Access Control Lists
      chmod 644 file1.txt       - Sets read and write permissions for the owner, and read-only permissions for others.
      chmod u+x script.sh       - Adds execute permission for the file owner on script.sh.
10. chown - Change file owner and group
      chown user file1.txt - Changes the owner of file1.txt to user.
      chown user:group file1.txt - Changes the owner of file1.txt to user                 and the group to group.