The Shell

As technology advances, so do the tools and skills required to work with it. One such tool that is essential for any developer or IT professional to know is the shell. The shell is a command-line interface that allows you to interact with your computer's operating system through text commands.

In this article, I will be sharing some of my learnings about the shell and important concepts related to it, including navigation, commands, and keyboard shortcuts.

RTFM: What Does It Mean?

Before diving into the shell, it's essential to understand the common acronym "RTFM," which stands for "Read the F*cking Manual." This acronym is often used in online forums and communities to indicate that a person should read the documentation or manual before asking a question.

Shebang: The First Line of a Shell Script

In shell programming, the shebang (#!) is the first line of a script that specifies the interpreter to use. For example, the shebang #!/bin/bash at the beginning of a script indicates that the script should be run with the Bash shell.

The Shell: What Is It?

The shell is a program that provides a command-line interface for interacting with the operating system. It acts as an intermediary between the user and the operating system, allowing users to execute commands and scripts, manage files, and navigate directories.

Terminal vs. Shell: What's the Difference?

Many people use the terms "terminal" and "shell" interchangeably, but they are actually different. The terminal is the application that allows you to interact with the shell. The shell is the program that interprets your commands and returns output.

Shell Prompt: What Is It?

When you open a terminal, you'll see a prompt that looks something like this: username@hostname:~$. The shell prompt displays information about the current working directory and provides a place for you to enter commands.

Using the History: Basic Commands

The history command is a powerful tool for accessing and repeating previously executed commands. To view your command history, simply type "history" in the terminal. You can then use the "!" symbol followed by the command number to execute a specific command from your history.

Navigation: cd, pwd, ls

The cd command is used to change directories, while the pwd command displays the current working directory. The ls command lists the contents of a directory.

Navigating the Filesystem: . and ..

The "." directory represents the current directory, while the ".." directory represents the parent directory.

Working Directory: Printing and Changing

The working directory is the directory in which you are currently located. You can print the current working directory using the "pwd" command and change the current working directory using the "cd" command.

Root Directory: What Is It?

The root directory is the top-level directory in the filesystem. It is represented by the "/" character.

Home Directory: How to Navigate There

The home directory is the default directory for a user. You can navigate to your home directory using the "cd ~" command.

Root Directory vs. Home Directory of the User Root

The root user's home directory is "/root," while the root directory is "/".

Hidden Files: How to List Them

Hidden files are files that are not displayed by default when using the "ls" command. You can display hidden files by using the "-a" option with the "ls" command.

Using the "cd -" Command

The "cd -" command is used to switch between the current and previous working directories.

Looking Around: ls, less, file

The "ls" command is used to list the contents of a directory, while the "less" command allows you to view the contents of a file one page at a time. The "file" command is used to determine the type of a file.

Manipulating Files

Now that we've covered how to navigate the filesystem and look around, let's talk about manipulating files. The most commonly used commands for file manipulation are cp, mv, rm, and mkdir.

The cp command is used to copy files from one directory to another. The syntax is as follows: cp [source] [destination]. For example, to copy a file named "example.txt" from the current directory to a directory named "documents," you would type: cp example.txt documents/.

The mv command is used to move files from one directory to another. The syntax is similar to that of cp: mv [source] [destination]. However, instead of copying the file, it moves it to the new location. For example, to move a file named "example.txt" from the current directory to a directory named "documents," you would type: mv example.txt documents/.

The rm command is used to delete files. Use this command with caution, as it permanently deletes the file and it cannot be recovered. The syntax is as follows: rm [filename]. For example, to delete a file named "example.txt," you would type: rm example.txt.

The mkdir command is used to create a new directory. The syntax is as follows: mkdir [directoryname]. For example, to create a new directory named "documents," you would type: mkdir documents.

Wildcards

Wildcards are special characters that allow you to match filenames based on patterns. The most commonly used wildcards are the asterisk (*) and the question mark (?). The asterisk matches any number of characters, while the question mark matches a single character.

For example, if you wanted to copy all files in the current directory with the word "example" in the filename to a directory named "backup," you would type: cp example backup/. The asterisks on either side of "example" match any number of characters before and after the word.

Working with Commands

The type command is used to display information about a command. For example, typing "type ls" would display information about the ls command.

The which command is used to display the location of a command. For example, typing "which ls" would display the location of the ls command.

The help command is used to display help information about a command. However, not all commands have a help function.

The man command is used to display the manual page for a command. The syntax is as follows: man [command]. For example, to display the manual page for the ls command, you would type: man ls.

Aliases

An alias is a custom shortcut for a command or group of commands. For example, you could create an alias for "ls -l" that is triggered when you type "ll". To create an alias, use the following syntax: alias [shortcut]='[command]'. For example, to create an alias for "ls -l" that is triggered by typing "ll", you would type: alias ll='ls -l'.

Reading Man Pages

Man pages are the built-in documentation for commands in the Unix and Linux operating systems. They provide detailed information about a command, including its syntax, options, and examples. The man pages are divided into sections, with each section covering a different topic.

We will end our discussion of the shell here. However the shell is a powerful tool that is still widely used in the tech industry even today. Learning will definitely not be a waste of time.