Mastering UNIX® Shell Scripting: Bash, Bourne, and Korn Shell Scripting for Programmers, System Administrators, and UNIX Gurus, Second Edition

CHAPTER14

Number Base Conversions

On many occasions in computer science you need to convert numbers between different number bases. For example, you may need to translate a hexadecimal number into an octal representation, or if you are a software developer you may want to license the software you create for a specific machine. One way of creating a machine-specific license key is to use the IP address of the machine to create a hexadecimal character string, which will allow the software to execute only on that specific machine. The first example here is a common occurrence, but the latter one is a little more obscure.

In this chapter we are going to present some number base conversion techniques and also show how to create a shell script that produces a license key, as in our second example. Converting between number bases is very straightforward, and we are going to go through each step. Before we can write a shell script we need the correct command syntax. In this case we add setting up the proper environment for the system to do all of the hard work automatically.

Syntax

By far, the easiest way to convert a number from one base to another is to use the typeset command with the -ibase Korn shell option, specifying a valid shell-supported base between base 2 and base 36. Bash and Bourne shells do not support this particular typeset command notation. The typeset command is used a lot in this book, mostly to force a character string to uppercase or lowercase and to classify a variable ...