Introducing UNIX and Linux

Processes and devices

Overview
Processes
      Process status
      Foreground and background
      Process control
      Signals
Environment
      Environment variables
      Global and local variables
      Executable scripts
Program control
      Job control
      Command history list
      Running a job at a specific time
      Running programs periodically
      Big programs
      Timing a program
      Running programs in order
Quotes and escapes
Devices
Backquotes
Summary
Exercises

Environment

Another communication mechanism employed by UNIX is that of the environment. If you are already familiar with a programming language, the environment is a collection of variable names together with an associated value for each one. Unlike most other languages, variables in UNIX are usually regarded as character-strings, and only interpreted as numbers (or other data types) in specific circumstances.