When connected to a Unix system via the shell, understanding how to navigate the file system is essential. This section covers fundamental commands for moving around and exploring directories.

Note: The sample outputs below are examples. Your system’s output may differ based on your files and directory structure.

pwd

  • Description: Prints the current working directory (the directory you are currently “in”).

  • Example Usage:

    pwd

    Sample Output:

    /home/user/projects

ls

  • Description: Lists the contents of a directory.

  • Example Usage:

    ls           # Displays files and directories in the current directory
ls -l        # Displays detailed information (permissions, owner, size, date)
ls -a        # Displays all files, including hidden files (those starting with .)
ls -la       # Combines -l and -a: detailed info, including hidden files
ls -lt       # Sorts by modification time, newest first

    Sample Output (for ls):

    file1.txt  my_folder  another_file.pdf

man

  • Description: Displays the manual page (documentation) for a command. This is your best friend for learning about commands!

  • Example Usage:

    man ls  # Shows the manual page for the 'ls' command

    Important Note: On some systems (like Debian/Ubuntu), you might need to install the man-db package first:

    sudo apt install man-db  # Use this on Debian/Ubuntu if 'man' doesn't work

    (On other distributions, the package manager might be different, e.g., yum on CentOS/Fedora, or pacman on Arch.)

mkdir

  • Description: Creates a new directory.

  • Example Usage:

    mkdir new_directory  # Creates a directory named 'new_directory'

    Sample Output: (No output is printed to the console if the command is successful)

cd

  • Description: Changes the current working directory.

  • Example Usage:

    cd my_folder       # Moves into the 'my_folder' subdirectory
cd ..             # Moves up one level (to the parent directory)
cd ~/Documents     # Moves to the 'Documents' folder inside your home directory
cd -              # Moves to the previously visited directory
cd /              # Moves to the root directory of the file system

Directory Symbols

These symbols are shortcuts for common directory locations:

  • . : Represents the current directory.
  • ..: Represents the parent directory.
  • - : Represents the previous directory.
  • ~: Represents your home directory (e.g., /home/user).
  • /: Represents the root directory.

Wildcards: * and ?

Wildcards are special characters used to match multiple files or directories.

  • * (Asterisk): Matches zero or more characters.

    • Example Usage (with ls):

      ls *.txt  # Lists all files ending with '.txt' (e.g., file1.txt, report.txt, notes.txt)
           # Will NOT match .txtfile (because * needs zero or more chars BEFORE .txt)
ls docs/* # Lists all files and directories inside the 'docs' directory

  • ? (Question Mark): Matches exactly one character.

    • Example Usage (with ls):

      ls file?.txt  # Lists files like file1.txt, fileA.txt, file9.txt
              # Will NOT match file10.txt (because ? matches only ONE character)
              # or file.txt

tree

  • Description: Displays a tree-like diagram of a directory’s structure. This command is often not installed by default.
  • Installation (Debian/Ubuntu): 
    sudo apt install tree

    (Installation for other distributions will vary)

  • Installation (CentOS/Fedora):

    sudo yum install tree

  • Example Usage:

    tree        # Shows the tree structure of the current directory
tree /home/user/projects # shows from the /home/user/projects directory
tree -L 2  # Limits the display to 2 levels deep

    Sample Output (truncated):

    .
├── my_folder
│   ├── file1.txt
│   └── file2.txt
└── another_folder
    └── notes.md

2 directories, 3 files