Networking / Beginners

Environment variables

The shell makes several environment variables available to commands. You can use an environment variable anywhere in a command by typing $ (dollar sign) followed by the environment variable name. For example, this command

$ echo This is $HOSTNAME running on an $HOSTTYPE

displays a line such as

This is LSERVER running on an i386

Table below lists some of the more useful environment variables that are available to you and your commands.

Environment Variables

VariableDescription
HOMEThe current user's home directory.
HOSTNAMEThe computer's host name.
HOSTTYPEThe host computer type.
OSTYPEThe operating system.
PATHThe search order for executable programs.
PROMPT_COMMANDThe command used to generate the prompt.
PWDThe present working directory.
SHELLThe shell being used.
USERNAMEThe current username.
[Previous] [Contents] [Next]

In this tutorial:

  1. Linux Commands
  2. Command Shell Basics
  3. Editing commands
  4. Wildcards
  5. Redirection and piping
  6. Environment variables
  7. Shell scripts
  8. Directory and File Handling Commands
  9. The cd command
  10. The mkdir command
  11. The rmdir command
  12. The ls command
  13. The cp command
  14. The rm command
  15. The mv command
  16. The touch command
  17. The cat command
  18. Commands for Working with Packages and Services
  19. The rpm command
  20. Commands for Administering Users
  21. The usermod command
  22. The chage command
  23. The passwd command
  24. The newusers command
  25. The groupadd command
  26. The groupdel command
  27. Commands for Managing Ownership and Permissions
  28. The chgrp command
  29. The chmod command
  30. Networking Commands
  31. The ipconfig command
  32. The netstat command
  33. The ping command
  34. The route command
  35. The traceroute command