Sams Teach Yourself Shell Programming in 24 Hours, Second Edition

The bc Command

The bc command is an arithmetic utility not limited to integers:

$ bc
scale=4
8/3
2.6666
2.5 * 4.1/6.9
1.4855
quit
$

In this example, you invoke bc and set scale to 4, meaning that you want it to calculate any fraction to four decimal places. You ask it to calculate 8/3, which gives 2.6666 and then a more complex calculation. Note that spaces are optional. Finally you enter quit to return to the shell prompt. bc can handle addition (+), subtraction (-), multiplication (*), division (/), remainder or modulo (%), and integer exponentiation (^). It can accurately compute numbers of any size

9238472938742937 * 29384729347298472
271470026887302339647844620892264

and can be used in shell variable assignment to assign calculated values ...