Linux command line basics every developer needs

The commands you will actually use: moving around, working with files, permissions, pipes and grep, processes and ports, packages and SSH, plus the safety habits that prevent disasters.

The Linux command line lets you control a computer by typing commands instead of clicking, and most servers, cloud machines and developer tools run on it. Every developer needs a core set: moving between folders, managing files, reading permissions, combining commands with pipes, searching with grep, managing processes, installing packages and connecting to servers with SSH.

You do not need to memorise hundreds of commands. About twenty-five cover most daily work. This guide explains them in the order you will need them, with examples to try, and ends with the habits that keep you from deleting the wrong thing.

Why do developers need the terminal?

How do you get a terminal?

On Linux and macOS, open the Terminal app; macOS uses a very similar Unix command line. On Windows, the easiest route is the Windows Subsystem for Linux, which runs a real Linux environment inside Windows; Microsoft’s WSL installation guide walks you through it.

How do you move around?

The terminal always has a current folder, called the working directory. These commands let you see where you are and move:

pwd                 # print where you are
ls                  # list files
ls -la              # list all files, including hidden ones, with details
cd projects         # move into a folder
cd ..               # move up one level
cd ~                # go to your home folder

Press Tab to auto-complete file and folder names. It saves typing and prevents typos, and it is the single most useful habit to build early.

Which commands work with files?

tail -f deserves a special mention: it follows a log file live as new lines are written, which is how you watch a server while testing it.

What do file permissions mean?

Run ls -l and you will see strings such as -rwxr-xr--. After the first character, they come in three groups of three: permissions for the owner, the group and everyone else. r is read, w is write and x is execute.

chmod +x deploy.sh        # make a script executable
chmod 600 secrets.env     # only the owner can read and write
sudo apt update           # run a command as administrator

How do pipes, redirection and grep work?

The real power of the command line is combining small commands. The pipe | sends one command’s output into another. Redirection > writes output to a file, and >> appends to it. grep searches text.

grep "ERROR" server.log                    # lines containing ERROR
grep -i "timeout" server.log | wc -l       # count them, ignoring case
grep -rn "API_KEY" src/                    # search a whole folder, with line numbers
ls -la > files.txt                         # save a listing to a file
history | grep git                         # find git commands you ran earlier

Once pipes click, you start seeing everyday tasks as small chains of commands.

How do you manage processes and ports?

Every running program is a process. When a server will not start because “the port is already in use”, these help:

ps aux | grep node         # find running node processes
top                        # live view of CPU and memory (q to quit)
kill 12345                 # stop a process by its ID
ss -tulpn                  # see which ports are in use (Linux)

Press Ctrl+C to stop the program currently running in your terminal.

How do you install software and reach servers?

Linux distributions install software through package managers. On Ubuntu and Debian, that is apt:

sudo apt update
sudo apt install git curl

SSH lets you open a terminal on a remote machine securely, which is how you manage cloud servers:

ssh-keygen -t ed25519            # create a key pair once
ssh [email protected]          # connect to a server
scp report.csv [email protected]:~/   # copy a file to it

Use SSH keys rather than passwords, and never share your private key file.

Can you automate tasks with scripts?

Any sequence of commands can become a shell script. Save this as backup.sh, make it executable, and run it:

#!/bin/bash
# Back up the project folder with today's date
tar -czf "backup-$(date +%F).tar.gz" ~/projects/my-app
echo "Backup done"

Small scripts like this are the start of the automation that DevOps and MLOps are built on. Program Zero’s explainer on what MLOps is shows where these skills lead when models go into production.

How do you find files and check disk space?

Two situations come up constantly: “where is that file?” and “why is the disk full?”. These commands answer both:

find . -name "*.log"            # find log files below the current folder
find . -name "*.py" -mtime -1   # Python files changed in the last day
df -h                           # free space on each disk, human-readable
du -sh *                        # size of each item in the current folder

On servers, full disks are a common cause of mysterious failures: databases stop writing, uploads fail and logs vanish. Running df -h early when something breaks often saves an hour of guessing. If du shows a huge logs folder, the fix is usually log rotation rather than deleting files by hand.

Environment variables are the other thing worth knowing early. echo $PATH shows where the shell looks for programs, and export NAME=value sets a variable for the current session. Many “command not found” errors are really PATH problems.

Which safety habits matter most?

For a structured, free reference, William Shotts’s book The Linux Command Line is excellent, and the GNU Coreutils manual documents the standard commands in detail. Once you are comfortable here, our guide to Git and GitHub for beginners is the natural next step.

The command line is where Program Zero begins: Phase 0 covers how computers work, Linux fundamentals, the command line and bash scripting, Git and how the internet works, before any programming language.

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