Cowsay

cowsay is a program that generates ASCII art pictures of a cow with a message. It can also generate pictures using pre-made images of other animals, such as Tux the Penguin, the Linux mascot. It is written in Perl. There is also a related program called , with cows with thought bubbles rather than speech bubbles. codice_1 files for cowsay exist which are able to produce different variants of "cows", with different kinds of "eyes", and so forth. It is sometimes used on IRC, desktop screenshots, and in software documentation. It is more or less a joke within hacker culture, but has been around long enough that its use is rather widespread. In 2007, it was highlighted as a Debian package of the day.
Example.
The Unix command can also be piped into the command:
[user@hostname ~]$ fortune | cowsay
 ________________________________________
/ You have Egyptian flu: you're going to \
\ be a mummy. /
 \ ^__^
 \ (oo)\_______
 (__)\ )\/\
 ||----w |
And using the parameter followed by , one can replace the cow with other beings, such as Tux, the Linux mascot:
[user@hostname ~]$ fortune | cowsay -f tux
 _________________________________________
/ You are only young once, but you can \
\ stay immature indefinitely. /
 \
 .--.
 |o_o |
 |:_/ |
 (| | )
 /'\_ _/`\
 \___)=(___/
Or other things:
[user@hostname ~]$ fortune | cowsay -f head-in 
 ________________________
< Don't get to bragging. >
 \
 ^__^ /
 (oo)\_______/ _________
 (__)\ )=( ____|_ \_____
 ||----w | \ \ \_____ |
Using the parameter shows all available cowfiles:
[user@hostname ~]$ 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
If a user wants to show examples of all the different cowfiles they can run this command:
[user@hostname ~]$ for i in $(cowsay -l); do cowsay -f $i "$i"; done
Once the user has this output they can either pipe:
[user@hostname ~]$ ls | cowsay -f tux
 ________________________________________
/ ChangeLog cows cowsay cowsay.1 INSTALL \
\ pgp_public_key.txt README Wrap.pm.diff /
 \
 .--.
 |o_o |
 |:_/ |
 (| | )
 /'\_ _/`\
 \___)=(___/
Or just cowsay their text:
[user@hostname ~]$ cowsay -f tux "This is my text."
 __________________
< This is my text. >
 \
 .--.
 |o_o |
 |:_/ |
 (| | )
 /'\_ _/`\
 \___)=(___/