command-line-basics.md

Command-Line Basics

This note summarizes the first layer of Linux shell fluency: locating yourself, moving through directories, listing files, and reading small text files.

Core Idea

Most command-line work starts with three questions:

• Where am I?
• What is here?
• What do I want to inspect or change?

The basic loop is:

pwd
ls
cd /path/to/directory

Current Directory

Use pwd to print the current working directory.

pwd

This is useful before running commands that read or write relative paths.

Moving Around

Common cd forms:

cd /absolute/path
cd relative/path
cd ..
cd ~
cd -

Notes:

• /absolute/path starts from the filesystem root.
• relative/path starts from the current directory.
• .. moves to the parent directory.
• ~ expands to the current user's home directory.
• - returns to the previous directory.

Listing Files

Common ls forms:

ls
ls -l
ls -a
ls -lh
ls -R

Useful reading:

• -l shows permissions, owner, group, size, and modification time.
• -a includes dotfiles.
• -h makes sizes human-readable when paired with -l.
• -R recursively lists subdirectories.

Reading Text

Use cat for short files:

cat notes.txt

Use less for files that may be longer than the terminal:

less system.log

Inside less, /pattern searches forward and q quits.

Use more only when it is already available in a simple environment. less is usually the more practical pager.

Practical Habit

Before changing files, run a quick context check:

pwd
ls -lah

This prevents many mistakes caused by assuming the wrong working directory.