Cowsay is a command line utility

Cowsay is a command-line utility on Unix and Unix-like operating systems that allows you to create ASCII-art drawings of cows and display their messages. Cowsay can report any textual information provided to it. The utility also supports various flags and parameters to customize the appearance and behavior of cow drawings. Cowsay is commonly used to add humor and personalize command line output.

How to use

It is very convenient to use for terminal greeting. You can install the program from the official Ubuntu repositories with the command:

 sudo apt-get install cowsay

You can use any other animal, a list of possible options is output with the command:

cowsay -l
Cow files in /usr/share/cowsay/cows:
apt beavis.zen bong bud-frogs bunny calvin cheese cock cower daemon default
dragon dragon-and-cow duck elephant elephant-in-snake eyes flaming-sheep
ghostbusters gnu head-in hellokitty kiss kitty koala kosh luke-koala
mech-and-cow meow milk moofasa moose mutilated pony pony-smaller ren sheep
skeleton snowman sodomized-sheep stegosaurus stimpy suse three-eyes turkey
turtle tux unipony unipony-smaller vader vader-koala www

Then, to select an option use the -f option. For example:

 cowsay -f dragon "Hello World"