Whenever you operate a Linux system behind the scenes, you might be encountering the interactive login or non-login shell that you are not aware of.

The printenv command is an alternative to the env command used to fetch the value of a specified variable name (key) used as an argument.

The env command is an advanced version of printenv with a few more features to tweak your environment variables, like setting new environment variables, printing all environment variables, or executing a command in a modified environment.

The source is a built-in command-line tool that reads and executes the commands from the specified file as its argument in the current shell.

The bash (Bourne-Again SHell) is a sh-compatible command-line interpreter that reads from standard input or from a file and gives you the resulting output.

Bash, an acronym for “Bourne-Again SHell“, is a superset of the shell (or sh) program written by Brian Fox for the GNU Project as a replacement for the traditional Bourne Shell (or sh).

To avoid jumping into the directory to execute your local program or script, you can add their paths to the $PATH variable to access them from anywhere.

In Linux, multiple long commands can be easily replaced with a single short command using the alias command.

In Linux, the alias command is used to create shortcuts for long commands that have the same functionality as if you were writing the whole command.

The eval command is used to execute specified arguments as a single command in the current command-line processing and return its result.

The WC command is used to count various parameters from the specified file, like the number of lines, word counts, byte counts, character counts, and many more.

In this article, you will learn to count the number of string occurrences in a text file using the grep, wc, and tr commands, including the VIM text editor.

The absolute and relative paths are different ways to navigate through directories in your Linux file system that everyone must know.

Learn how to write and run a shell script using the bash or source command, or run it from the URL and execute it using its path.

The PS is a native command-line utility for UNIX-based systems that monitors the currently running processes in your system.

The export command is used to create environment variables or update variable values in the current shell session by newly forked child processes without starting a new shell session.

The set command is a built-in Linux command that can display or modify the value of shell attributes and positional parameters inside the current shell environment.

The unset command is a built-in Linux command used for flushing the value of variables or functions during program execution.

The “$?” is a built-in variable that your shell uses to store the exit status code of the last executed command in integer format and remains unchanged unless the next command is executed.

The "#! /bin/bash" in Linux, famously known as shebang or hashbang, starts with a pound/hash ("#") sign together with an exclamation ("!") sign.