Intro to Bash Shell Commands

June 14, 2022
4 min read

We talk to our computer’s operating system (OS) all the time. Most of us do this through a graphical user interface (GUI), with icons,windows, and fancy visuals that make it pleasing to the eye to interact withour computers. Another – more powerful – way to do this is through what’scalled a command-line interface, enabling a higher level of communication withthe computer. A popular way to interact through this interface type is the Bash scripting language which we’ll work up to focusing on.

Command Line Interface

The command line interface is a computer program that enables you to talk to and navigate a computer and files. On is what’s called the Terminal on Mac and for Windows it’s the Command Prompt.

To communicate through this interface, we use what’s called a command-line interpreter (CLI). This is the part of a computer OS that understands and executes commands from human/program input. In some OSs, the CLIis referred to as the shell. Common shells used today include:

Bash (Bourne-again SHell) – A Unix shell and used by default in Linux distributions. The name is a pun on the shell it superset (Bourne shell) and its author (Stephen Bourne). We’ll be looking at this Bash and some of its commands more in depth.

Zsh (Z shell) – An extension of Bash and the current default CLI for MacOS.

PowerShell – Not quite a shell per-say, PowerShell is Microsoft’s task automation and configuration management program including a CLI and the associated scripting language.

The Bash Prompt

The first thing you’ll see pop up in a Linux Terminal when launching it is something like this:

   <username>@<hostname><current working directory>$

Here, the dollar sign stands for a user. The default folder (AKA directory) we start out in when we first log in is the home directory denoted by a tilde:

   <username>@<hostname><~>$

From here we can start typing in Bash commands to communicate with the OS! Heads up, it's best practice to use a Virtual Machine (VM) while learning so you can play around without the worry of accidentally harming your computer.

 

Commands and Flags

The number of available commands to use in with the Bash shell is overwhelming not to mention the different ways you can use each command.If you’re ever unsure of a command’s use, input options, flag options, or Feel like learning more about it, use the man command followed by the command in question to display it’s manual.

As mentioned, most Unix shell commands have multiple flag options to invoke while using it. These allow you to tailor a command along with its arguments. These are either denoted by a single (-) or double (--) dash followed by a letter or sequence of letters. Again, use man to see a command’s possibilities and the particular syntax!

Directories

One of the most important uses of the CLI is navigating and managing a system’s directories and the files they contain:

pwd      Print current working directory

cd      Changes one’s directory in relation to their current directory

cd ~      Navigate directly to the home directory

cd ..      Navigate up one directory level

cd -      Navigate to the previous directory

cd /      Navigate into the root directory

mkdir      Make directories

rmdir      Remove directories – BE CAREFUL WITH THIS COMMAND

cp      Copy files

touch      Change file access and modification times / create file with default permissions if file doesn’t exist

rm      Remove/delete files – BE CAREFUL WITH THIS COMMAND

ls      List directory contents

 ls -a      Don't ignore entries starting with “.” (hidden files/directoriesunseen in the GUI)

ls -l      Use a long listing format

ls -h      With -l and -s, print sizes

System Information Commands

Interacting with different Linux systems, it’s important to learn as much information about the system as possible. Here’s a list command tools that will help with this, most automatically installed:

whoami      Displays effective user id

id      Return user identity

hostname      Set or print name of current host system

uname      Print operating system name

ifconfig      Configure network interface parameters

ip      Internet Protocol

netstat      Show network status

ss      Another utility to investigate sockets

ps      Process status

who      Display who is logged in

env      Set environment and execute command, or print environment

lsblk      List block devices

lsusb      List USB devices

lsof      List open files

lspci      List all PCI devices

 

Conclusion

To end a session in the shell, you can use the exit command. Now you have a basic grip on Bash commands! For more information,check out our other posts below! Stay tuned to the writings.

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