Startup Files

1
Startup Files

• How to customize your Unix login shell.

2
Shells

• Remember that you always interact with a Unix
  system through a shell.
• Alphas by default use the EZ-shell.
• This can be changed.
• chsh user name
• Many different shells exist
• C-shell, korn shell, bourn shell, t-shell,
  ez-shell, etc.

3
Initialization files (Control files)

• Files that are used at the start of a login or
  the start of a program.
• Like preference files on Macs or PCs.
• .login
• .cshrc
• .forward
• .plan
• .pinerc
• .elm
• .emacs

4
Login and Shell Initialization Files

• Two types of startup files
• login initialization files which execute every
  time you log into the computer.
• shell initialization files which execute every
  time you start a new shell.
• In practice, you really only need to modify your
  shell initialization file.

5
Variables

• Two kinds of variables exist
• Environmental variables
• Exist system wide.
• Used by the system to allow it to work properly.
• User-created variables
• A user can create his or her own variables.
• Also called aliases which are shortcuts to
  commands.

6
The C-shell

• .login file
• used to set variables once per login.
• .cshrc file
• used to set variables for each shell.
• Not much difference between the two.
• Best to modify just your .cshrc file.
• Make a backup copy of your .cshrc file before
  modifying it!

7
Listing Environmental Variables

• setenv
• Lists the current environmental variables for
  your login.
• Common ones include
• TERM, HOME, SHELL, MAIL, PATH
• Note the UPPERCASE

8
C-shell Special Variables

• In addition to environmental variables, the
  C-shell has its own special variables.
• set
• Include things like
• history, noclobber, editmode, term, home, path,
  etc.
• Note the lowercase.

9
Setting Environmental Variables

• Simple format
• setenv variable name value
• Can be set from the command line or from the
  .cshrc file.
• Make sure you make a backup of your .cshrc file
  before changing it!

10
Setting Special Variables

• Simple format
• set variable name value
• Can be set from the command line or from the
  .cshrc file.
• Make sure you make a backup of your .cshrc file
  before changing it!
• Note that special variables will override
  environmental variables.

11
Aliases

• Alias is an alternate name for a command.
• Can create them on the command line or in your
  .cshrc file.
• Like variables, when created from the command
  line, they exist only for that login.
• Format
• alias name command
• Can be especially useful for changing default
  behavior for common commands.

12
Reading

• Chapters 25 and 27.
• We are done, take the exam.