Scripting by Numbers
Number crunching was once the domain of big mainframe computers hidden away in secure, air-conditioned rooms. Now, the computer on your desk (or even the one in your pocket) has more computing power than those old behemoths. The shell, with the help of external commands, can harness that power.
POSIX shells have arithmetic built in, but are limited to integers. Multiplication of decimal fractions can be done in the shell with the fpmul function, which appears in the math-funcs library described next. Other operations could also be coded with shell arithmetic, but they are more complicated, and external commands ...