2.3 Using Directories and Listing Files

2.3 Using Directories and Listing Files

Quick Answer: Everything on a Linux system lives in one directory tree rooted at /. You move with cd, see names with ls, and address locations with absolute paths (from /), relative paths (from where you are), or ~ for your home. Dotfiles stay hidden until you ask ls to show them with -a or -A.

Objective 2.3 is about finding your way: files vs directories, paths, home, hidden names, cd, and ls.

Files Versus Directories

A file stores content (text, a program, an image). A directory stores a list of names that refer to other files or directories. Directories form a hierarchy: each directory except / has a parent, and most have children.

On the command line you work with pathnames. Two styles matter on every location question:

Absolute paths always mean the same place. Relative paths change when you cd. Confirm location with pwd if unsure.

Home Directories and ~

Each normal user has a home directory—a personal starting place for documents and configuration. On most systems that path looks like /home/username. The root account’s home is usually /root.

The shell expands ~ to the current user’s home directory:

cd ~
cd ~/Documents
ls ~/.

Bare cd with no arguments also returns you to your home directory—the same destination as cd ~. Many Essentials tasks happen under ~, while system files live under absolute paths such as /etc.

Hidden Files and Directories

Any name that begins with a dot (.) is a hidden file or directory: .bashrc, .ssh, .config. Hidden does not mean encrypted—it only means ordinary listings skip those names.

ls              # omits names that start with .
ls -a           # show all entries, including . and .. and hidden names
ls -A           # almost all: hidden names, but usually not . and ..

Exam trap: If a question asks how to see .bashrc in a listing, the answer involves -a or -A (or an explicit path to that name), not a second ls with no options.

Absolute Paths, Relative Paths, ., and ..

Two special directory names appear in every listing that includes them:

Use them constantly in relative paths:

cd ..
cd ../..
ls ./scripts
cp ../shared/config.txt .

From /home/alex, relative projects/app matches absolute /home/alex/projects/app. From that app directory, .. is projects and ../.. is home.

Worked path scenario

Suppose pwd prints /home/sam/lab:

/home/sam/
  lab/
    notes.txt
    data/
      sample.csv
  .bashrc

Same destination, three path styles—practice reading all three on sight:

ls /home/sam/lab/data/sample.csv   # absolute from /
ls data/sample.csv                 # relative from /home/sam/lab
ls ~/lab/data/sample.csv           # via home shortcut
ls ./data/../notes.txt             # . and .. cancel; resolves to notes.txt here
ls ../../etc/hosts                 # climb toward root (from deep under /home)

If you cd /tmp first, ls data/sample.csv no longer finds Sam’s file, but ls /home/sam/lab/data/sample.csv and ls ~/lab/data/sample.csv (for user sam) still do. That contrast is the exam point of absolute versus relative paths.

Changing Directories With cd

cd (change directory) updates your current working directory:

cd /etc
cd /home/alex/projects
cd ..
cd ~
cd

Prefer absolute paths for distant jumps (cd /var/log), relative paths for nearby moves (cd docs, cd ..), and cd / cd ~ to reset home. If cd fails with “No such file or directory,” the path is missing or mistyped—and remember Linux names are case-sensitive.

Listing With ls and Common Options

ls lists directory contents. Alone, it lists the current directory in a short view.

ls
ls /etc
ls ~/lab

Options you must recognize

Flags combine. Everyday combos:

ls -la              # long + all (including hidden)
ls -lah ~/Downloads # long, all, human-readable sizes
ls -l /etc/hosts    # long details for one file
ls -ld /etc         # long details for the /etc directory itself
ls -R projects      # recursive tree listing under projects
ls -lR ~/lab        # long + recursive under home lab
ls -la /home/sam/.ssh   # absolute path into a hidden directory
ls -ld ~/lab data       # metadata for each named directory, not their children

Without -R, ls projects shows only direct children. With ls -R projects, nested folders and their contents appear too—-R means descend into subdirectories. Compare ls ~/lab (one level) with ls -R ~/lab (every nested name under that tree).

ls -l /tmp shows what is inside /tmp. ls -ld /tmp shows metadata for the directory itself. Questions about “the directory, not its contents” point at -d. You can also pass several targets: ls -l /etc/hosts ~/lab/notes.txt lists those two files without changing directory.

Putting Navigation and Listing Together

pwd                 # where am I?
ls -la              # what is here, including hidden?
cd ~/lab
ls -lah
cd ..
ls -R data          # peek the subtree before entering it

Master these moves before creating or deleting anything—wrong directory plus a powerful rm is how beginners erase the wrong tree.