Java™ Application Development on Linux - Dator

4.3 The System Class105several successively executed programs. Some examples of environmentvariables are:• USER is the name you used to log in.• HOME is the directory where you start when you log in.• PATH is the list of directories searched for executable files.To see the environment variables defined in your current shell, type envat the command prompt:$ envHOME=/home/user01USER=user01PATH=/bin:/usr/bin:/usr/local/bin:/home/user01/bin...$The names of environment variables, sometimes referred to as shell variables,are traditionally uppercase, though that is only a convention. The variablenames are treated in a case sensitive fashion (e.g., Home != HOME).You can set environment variables for use in the current shell with a simpleassignment statement:$ VAR=valueThat will set the value for the duration of this shell, but not for any of its subprocesses.Since running another program is a subprocess, such an assignmentwon’t be visible in your running program. Instead, you can export the variableso that it is carried forward to all subprocesses: 1$ export VAR=value4.3.3 Java and Environment VariablesIf these environment variables are available to all Linux processes, then how dowe get at them from a Java program? Well, we can’t do it quite as directly asyou might think. In previous (1.2 and older) versions of Java, the System class1. If you are using csh (the C-shell, another Linux command-line interpreter), then the syntaxis slightly different. Instead of export name=value use setenv name value (note thedifferent keyword and no equal sign).