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Linux Tutorial Series

Linux Tutorial Series – 12 – What is a shell?

Here is the video version, if you prefer it:

The shell, the shell… We all heard that. We know you can type some command in the shell in a Linux environment and get some output. But what does the shell actually mean?

“A shell is a program that runs commands”, says (Ward, 2014)⁠. That is basically it. You type some commands in, the shell executes them, then you get some output. Shell scripts, another popular term, are essentially just commands typed in a file called a shell script; so the shell has the same job – execute commands.

There are multiple kinds of shells. You can find more information here: (“5 Most Frequently Used Open Source Shells for Linux,” n.d.)

Before I end, it is important to note that programs like Terminal are not actually shells – they are graphical user interfaces running shell on your behalf. (Barrett, 2016)⁠ Figure 1 depicts this. This program with a graphical user interface, called a terminal emulator, interacts with the shell. (Shotts, 2019)⁠

Figure 1 – Relationship between graphical user interfaces to the shell and the shell itself (modeled after figure on page 15 of (Barrett, 2016)⁠)

Hope you learned something new!

References

5 Most Frequently Used Open Source Shells for Linux. (n.d.). Retrieved December 22, 2019, from https://www.tecmint.com/different-types-of-linux-shells/

Barrett, D. J. (2016). Linux pocket guide (3rd ed.). O’Reilly Media. Page 15

Shotts, W. (2019). The Linux Command Line, Fifth Internet Edition. Retrieved from http://linuxcommand.org/tlcl.php. Page 26

Ward, B. (2014). How Linux Works: What Every Superuser Should Know (2nd ed.). No Starch Press. Page 12

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