Performing Math

Another feature crucial to any programming language is the ability to manipulate numbers. Unfortunately, for shell scripts this process is a bit awkward. There a two different ways to perform mathematical operations in your shell scripts.

The expr Command

Originally, the Bourne shell provided a special command that was used for processing mathematical equations. The expr command allowed the processing of equations from the command line, but it is extremely clunky:

The expr command recognizes a few different mathematical and string operators, shown in Table 10.1.

Table 10.1 The expr Command Operators

Operator	Description
ARG1 | ARG2	Return ARG1 if neither argument is null or zero; otherwise, return ARG2.