Bash Glossary

This is a non-exhaustive list of common, helpful bash commands and special characters

Bash Command Structure

Generally, all bash commands follow the format:

<executable> <options> <arguments>

• <executable> is the program that you are running (executing) with the command.
• <options> (also known as 'flags') change the way the program works in some way and are usually optional. They are often denoted with a single dash (e.g. -r) or double dash (e.g. --recursive) with a character/word following it.
• <arguments> are provided to the program to give it information, such as a file or string. Most commands take arguments, but not all.

Special Characters

Some characters in bash have special meanings. Here are some of the most common:

character	meaning	example
	Whitespace is a special character that "tokenises" the command. Essentially, each part (token) of a bash command is defined based on where the spaces are	echo Hello – the whitespace in this command tells bash where the executable's name ends and the argument begins.
.	Represents the current working directory.	git add . – stages all files in the working directory for commit
..	Represents the current parent directory (i.e. the directory that the current working directory is in).	cd .. – changes the working directory to the parent directory, essentially allowing you to 'go back' one directory.
*	Globbing wildcard. On its own, represents all files in the current working directory except hidden files (i.e. files that start with ., e.g. .ssh). Can be used in expressions to respresent files that fit a pattern.	cp *.txt my-folder – copies all files that end in .txt in the current directory to the my-folder directory.
\	Defines an escape character.	echo Hello \n World – prints 'Hello' to one line and 'World' to the next, because \n is an escape character representing a newline \
$	Used for both variable (${variable}) and command ($(command)) substitution.	PERSON=$(whoami) – assigns the output of the command whoami to the variable PERSON.
		echo ${PERSON} – prints the value of the PERSON variable to the console.

Navigation

command	options	arguments	description
cd		<file_path>	Change Directory
pwd			Print working directory
ls		(optional) <file_path>	Lists files in a directory – if no argument is provided, it will list the files in the current working directory
	-l	(optional) <file_path>	Show a detailed list
	-a	(optional) <file_path>	Show all files (files/directories that start with . are hidden by default)

Displaying Information

command	options	arguments	description
echo		<string>	Prints a string to the console on the next line
cat		<file_path>	Prints the contents of a file to the console on the next line

Managing Files

Creating Files

command	options	arguments	description
touch		<file_name>	Creates a new empty file with the name given as an argument
mkdir		<directory_name>	Creates a new empty directory with the name given as an argument
	-p	<directory_name>	Creates any parent directories specified in <directory_name> if they do not exist

Moving Files

command	options	arguments	description
mv		<source> <target>	Moves the file at the <source> location to the <target> location (also used to rename files)
cp		<source> <target>	Copies the file at the <source> location to the <target> location

Deleting Files

command	options	arguments	description
rm		<file_name>	Removes (deletes) a file
	-r	<file_name>	Delete recursively – deletes a directory and all files contained within
rmdir		<directory_name>	Removes (deletes) a directory

SSH

command	options	arguments	description
ssh		<user_name>@<host_name>	Log into a remote machine via SSH. <user_name> is the user you are logging in as, <host_name> is the location of the machine you're connecting to (typically an IP address).
	-i <private_key_path>	<user_name>@<host_name>	Specifies the path to the private key. If omitted, it will default to using ~/.ssh/id_rsa.
ssh-keygen			Generate a new SSH key pair. Leaving each text prompt blank will generate a key pair at ~/.ssh/id_rsa / ~/.ssh/id_rsa.pub.

Users

command	options	arguments	description
su		- <user_name>	Switch user. Typically prefixed with sudo.