Linux shell is a feature/program in the Linux system that takes instruction from the user typed via keyboard and translates it to machine language for OS to be able to interpret and process. Is simply a program that provides a command line interface for Unix-like systems. Linux Shell can be drawn back to 1971 when the first Unix shell called Thompson shell (/bin/sh) was invented. This shell was independent and executed outside the kernel.

Beyond 1977, the evolution of technology and looking for an alternative Linux shell to the Thompson shell. Other shells such as the Bourne shell came into existence which led to the development of the Almquist shell (ash) and the Bourn again shell (Bash)

In this guide, we are going to talk about the Fish shell, one of the most popular used shells in the Linux environment with a pretty interactive CLI. Specifically, we are going to discuss how to install Fish Shell and Oh My Fish on OpenSUSE.

Fish Shell and Its Features

This is an exotic Unix shell that is designed to provide users with an interactive command line interface. This command line can give you fun if you want to make it more productive without learning many syntax and configuration options. This is because Fish shell supports powerful features like;

• syntax highlighting
• Searchable command history
• Advanced tab completion
• Web-based configuration
• Advanced error messages
• Universal variables

Install Fish Shell on OpenSUSE / SUSE

Follow the steps below to install Fish Shell and Oh My Fish on OpenSUSE / SUSE.

Step 1: Adding repositories and installing Fish

OpenSUSE is an RPM-based Operating system that exists in different versions. To install Fish shell in OpenSUSE, first, add the Fish shell repo in the system as below.

For openSUSE Tumbleweed run the following as root:

zypper addrepo https://download.opensuse.org/repositories/shells:fish:release:3/openSUSE_Tumbleweed/shells:fish:release:3.repo
zypper refresh
zypper install fish

For 15.6, run the following as root:

zypper addrepo https://download.opensuse.org/repositories/shells:fish:release:3/15.6/shells:fish:release:3.repo
zypper refresh
zypper install fish

For 15.5, run the following as root:

zypper addrepo https://download.opensuse.org/repositories/shells:fish:release:3/15.5/shells:fish:release:3.repo
zypper refresh
zypper install fish

For 15.4, run the following as root:

zypper addrepo https://download.opensuse.org/repositories/shells:fish:release:3/15.4/shells:fish:release:3.repo
zypper refresh
zypper install fish

Verify that Fish has been installed:

$ fish -v
fish, version 3.7.1

Step 2: Creating Fish rc File.

A fish resource (rc) file is a configuration file that is used to store a predefined set of variables and functions to be used by the fish shell. This configuration file is at ~/.config/fish/config.fish

You can see what is to be executed on startup whether on interactive or login shell.

For instance, you can set a function to display a message when exiting the fish shell.

$ vim  ~/.config/fish/config.fish

Add below line of function in the file ad save. 

if status is-interactive
    # Commands to run in interactive sessions can go here
end
function on_exit --on-event fish_exit
    echo You are now exiting fish shell, Bye!!
end

The above function will display the “You are now exiting fish shell, Bye!!” message on leaving the fish shell with the [exit] command. 

devops@localhost ~> exit
You are now exiting fish shell, Bye!!

Step 3: Installation of Oh My Fish on OpenSUSE15

This is a Fishshell framework that can be used to modify your shell by using plugins and theme to make it more beautiful. Uses omf command that you can easily use in installing new features in fish shell such as themes and plugins and twerk your shell as you wish.

Step 3.1 Install Oh My Fish

Option 1:

You below command to install Fish shell using the installation script from GitHub or the Fish shell official site.

curl https://raw.githubusercontent.com/oh-my-fish/oh-my-fish/master/bin/install | fish
  #Or use below command.
curl -L https://get.oh-my.fish | fish

The above command will download and run the installation script of the Oh My Fish fish shell framework.

Option 2:

Download the install file then modifies your config to match your preferences.

curl https://raw.githubusercontent.com/oh-my-fish/oh-my-fish/master/bin/install > install
fish install --path=~/.local/share/omf --config=~/.config/omf

Option 3:

You can also install Oh My Fish from offline source

git clone https://github.com/oh-my-fish/oh-my-fish
cd oh-my-fish
bin/install --offline

#Out put of the above command
Installing package config
✔ config successfully installed.
Installing package spark
Submodule 'spark' (https://github.com/holman/spark) registered for path 'spark'
Cloning into '/root/.local/share/omf/pkg/spark/spark'...
Submodule path 'spark': checked out 'ab88ac6f8f33698f39ece2f109b1117ef39a68eb'
✔ spark successfully installed.
Installing package weather
✔ weather successfully installed.
Installing package default
✔ default successfully installed.
Installing package slacker
✔ slacker successfully installed.
Installing package slavic-cat
✔ slavic-cat successfully installed.
Installation successful!
Welcome to fish, the friendly interactive shell
~/oh-my-fish ☭ master ○

Step 4: Setting Fishshell Theme in Oh My Fish Framework.

Oh My Fish shell framework provides an awesome interface for the fish shells. It comes with a variety of themes to help user choose different themes depending on his/her preference. To show installed themes and plugins, use omf command.

⋊> ~ omf list                                      
Plugins
fish-spec	omf

Themes
Default

From above we note that only 2 plugins and one default theme is installed. 

To see only installed and available themes use this command.

 $ omf theme

	Installed:
default

Available:
agnoster		cmorrell		fishbone		harleen			lolfish			pastfish		separation		trout
aight			coffeeandcode		fishface		heartsteal		mars			perryh			simple			tweetjay
anchor			cor			fishy-drupal		idan			mint			pie			simple-ass-prompt	uggedal
ays			cyan			fisk			integral		mish			plain			simplevi		will
batman			dangerous		flash			jacaetevha		mokou			pure			slacker			wolf-theme
beloglazov		default			fluffy			johanson		mtahmed			pygmalion		slavic-cat		yimmy
bira			dmorrell		fox			kawasaki		nai			random			solarfish		zeit
bobthefish		doughsay		gentoo			kovial			neel			randomrussel		sushi			zephyr
boxfish			eclm			gianu			krisleech		nelsonjchen		red-snapper		syl20bnr		zish
budspencer		edan			gitstatus		l			neolambda		rider			taktoa
cbjohnson		eden			gnuykeaj		lambda			numist			robbyrussell		technopagan
chain			emoji-powerline		godfather		lambda-zero		ocean			sashimi			toaster
clearance		es			graystatus		lavender		one			scorphish		tomita

This is only theme installed and many more available themes which you can install with help of omf command. Before installing a theme, you can preview here to get one that interests. Having chosen one, run omf install <your-theme> to install the new theme.

For instance, to install slavic-cat theme run this. 

⋊> ~ omf install slavic-cat
Updating https://github.com/oh-my-fish/packages-main master... Done!
Installing package slavic-cat
✔ slavic-cat successfully installed.

By default, a new theme will be applied immediately due installation. To switch to another theme use omf command in this format; omf master <theme-name>

Step 5: How to Use omf Tool.

Update packages and repositories

$ omf update

List installed packages.

$ omf list

List available themes

$ omf themes

Installation of themes and plugins.

$ omf install <theme-name>
$ omf install <plugin-name>

Use OMF to remove packages and themes

$ omf remove <package name>

Updating Oh My Fish.

Oh My Fish framework is open-source and the version is being actively worked on resulting in new versions being created to improve features and performance. You can use the below command to update the OMF framework on OpenSUSE15.

 $ omf update     
Oh My Fish is up to date.
You are now using Oh My Fish version 7.
Updating https://github.com/oh-my-fish/packages-main master... Done!
config is already up-to-date.
spark is already up-to-date.
weather is already up-to-date.
default is already up-to-date.
slacker is already up-to-date.
slavic-cat is already up-to-date.

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