Bourne Shell Scripting/Appendix B: Environment reference

In the section on the environment we discussed the concept of environment variables. We also mentioned that there are usually a large number of environment variables that are created centrally in /etc/profile. There are a number of these that have a predefined meaning in the Bourne Shell. They are not set automatically, mind, but they have meaning when they are set.

On most systems there are far more predefined variables than we list here. And some of these will mean something to your shell (most shells have more options than the Bourne Shell). Check your shell's documentation for a listing. The ones below are meaningful to the Bourne Shell and are usually also recognized by other shells.