Unix 环境变量设置

1. Environment Variables

• operating system: type echo $OSTYPE
  show detail:

  USER: your login name
  HOME: the path name of your home directory
  HOST: the name of the computer you are using
  ARCH: the architecture of the computer processor
  DISPLAY: the name of the computer screen to display X windows
  PRINTER:  the default printer to send print jobs
  PATH:  the directory the shell should search to find a command
  

• environment set:
  type: setenv

• environment show:
  type: printenv or env

• environment unset:
  type: unsetenv

2. Shell Variables

• echo history: the vaule of how many shell commands to save
• cwd: current working directory
• home: the path name of your home directory
• path: the directories the shell should search to find a command
• prompt: the text string used to prompt for interactive commands shell

set or display shell variables:
type: set xxx
unset shell variables:
type: unset xxx
show all shell variables:
type: set | less

3. Using and setting variables

default file: ~/.login (C shell) or ~/.cshrc(TC shell)
~/.login: set conditions which will apply to the whole session and to perform actions that are relevant only at login.

~/.cshrc: set conditions and perform actions specific to the shell and to each invacation of it

recommand: set ENVIRONMENT variables in the .login file , and SHELL variables in the .cshrc file
warning: NEVER put commands that run graphical displays (e.g. a web browser) in your .cshrc or .login file

4. Setting shell variables in the .cshrc file

1. edit ~/.cshrc file: set history = 200
2. % source .cshrc
3. % echo $history

5. Setting the path

• % set path = ($path ~/xxx/xx/bin)
• add this line to .cshrc file: set path = ($path ~/xxx/xx/bin)