How do I print pi (3.14159)?

If you have tex(1) installed:

tex --version | head -1 | cut -f2 -d' '

You can use this command:

echo "scale=5; 4*a(1)" | bc -l
3.14159

Where scale is the number of digits after decimal point.

Reference: http://www.tux-planet.fr/calculer-le-chiffre-pi-en-ligne-de-commande-sous-linux/

For printing with arbitrary precision, you could use bc and the formula pi = 4*atan(1):

# bc -l
scale=<your precision>
4*a(1)