ZSH vs Bash: Unix shell in comparison

How does Z shell (ZSH) compare to the industry standard Bash shell?

DevOpsUPDATED ON March 14, 2022

Cover image for blog comparing and contrasting Z shell (ZSH) vs Bash shell

For years, the Bash shell has been the industry standard for Unix operating systems shells but it now has some genuine competition in the form of the more modern Z shell (ZSH), which has been gaining traction as an alternative. And it’s attracted some big users including Kali-Linux the standard distribution for security testing and Apple, who have both replaced Bash with ZSH as the default shell in their tech stack in recent years.

In this article we look at the role performed by Unix shells in software development and why it is worth comparing them. We will also examine what differentiates these two Unix shell technologies and why a growing number of users  are deciding to make the switch  from Bash to ZSH.

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What is a Unix shell?

A Unix shell such as ZSH or Bash is a user’s interface to the Unix system. Unix is an umbrella term for a group or family of operating systems that are all very similar and largely based on one technology. Unix systems are used in different technologies; the operating systems Linux and macOS are both Unix systems.

The shell is the casing of the operating system core. The Unix shell functions as an interface for communication between the Unix system kernel and the user. Direct communication would be far too complex. As illustrated below, the Unix shell can be understood as a translator layer between the system kernel and the user.

zsh vs bash: unix shell

Users type commands in the input line of the Unix shell, which can then be executed directly by the computer. This is why a shell is often referred to as a command line interpreter.

What is ZSH (Z shell)?

Z shell or ZSH is a Unix shell that can be used both as a command line interpreter and as an interactive login shell. ZSH is described by many developers as a modern, innovative shell with a variety of robust features, and is popular because of its effective command interpretation.

Developed in 1990 by former student Paul Falstad, the Unix shell is now available as open source technology. The technology, which is based on the Bash shell, is particularly known for its performance, which is considered superior to most other Unix shells. The continuous development of the open source technology has led to the implementation of useful functions from other Unix shells such as Ksh or Tcsh in ZSH. ZSH is an advanced Unix shell that has been the default shell for MacOS since the release of MacOS Catalina in 2019 and the default shell for Kali Linux since the end of 2020.

What is Bash (Bash Shell)?

The Bash shell is probably the most widely used Unix shell on Linux operating systems, especially since many popular Linux distributions such as Ubuntu or Arch use Bash as their default shell. It was even the default Unix shell on all Apple macOS versions until 2019’s release of macOS Catalina in which Bash was swapped out with the ZSH shell described above.

First released in 1989 and developed by Brian Fox, the open-source technology is popular for its robust feature set as well as its ease of use, among other things. It can be found on any standard Linux distribution, which is why most Linux users have likely come into contact with Bash at some point.

The use of Unix shells such as ZSH and Bash

Unix shells are interfaces between the computer core and the user. The shell executes the programme based on the input given by the user and gives the given output after execution. In simple terms, this is the function of a Unix shell. Linking to the core using a Unix shell allows interaction and execution of programs.

The uses and benefits of a Unix shell such as ZSH and Bash are many. Unix shells provide a set of commands and programs that can support work in many ways. In general, it is very interactive, as it lets the user give input to be executed. The shell allows several commands to be combined, which makes work generally more efficient. It saves time by allowing only one command to be written instead of multiple commands.

Large repetitive tasks can be done efficiently using Unix shell scripting, so especially in DevOps or system administration, Unix shell scripting skills can be beneficial.

ZSH vs Bash: Why many switch from Bash to ZSH

The Bash shell is arguably the default shell for most UNIX operating systems; it is a user-friendly, robust technology that is standard on Linux distros such as Ubuntu or Arch. However, many Linux users are choosing to switch to ZSH, following the lead of Kali Linux and macOS Catalina, which have also switched to Z shell (ZSH) relatively recently.

There are a number of considerations to be made, especially with ZSH versus Bash. Probably one of the most useful functions to be used in everyday life is the “TAB-Completion”. The “TAB-Completion” is a help that shows you a scrollable menu with all possible parameters for the previously entered command. When you enter a command and then press the “TAB key”, it shows a menu of possible executable commands which can make your work more efficient and easier.

There are also other very useful features such as automatic spelling correction (Typocorrection), the ability to use the directory without the usual cd command or the multi-session shared history which allows the shell history to be used during multiple sessions in different tabs. There are also some unique features like login/logout watching, closing comments, variable/functions index and other functions.

Users can easily switch to ZSH, especially via Ubuntu, because in Ubuntu, which uses Bash as the default shell, ZSH is in the repository. The following command installs ZSH on Ubuntu:

sudo apt-get install zsh

and this is how you replace Bash with ZSH in the terminal:

sudo chsh -s /usr/bin/zsh username


For most users, there will be no great reason to change their Unix shell. Especially for beginners or everyday users, the Unix shell provided by the operating system is generally sufficient. For productivity optimisers and programmers that make significant use of Unix shell scripting, a change may make sense. However, for standard users, it’s probably not worth migrating from Bash to Z shell with the former the default shell of so many systems for good reasons.

Not highlighted here, Bash also offers functions such as different shell functions, aliases or unlimited command sequences/indexed arrays. So, as with all other technologies, one should orient oneself to one’s own preferences, or the specific context, when making a choice between the two.

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