Introduction to UNIX

1
Introduction to UNIX

• G. Customizing the UNIX Environment

2
Customizing the UNIX Environment

• Performance Objectives
• 1. Describe the purpose of "Dot" files
• 2. Add a path variable to the .cshrc file
• 3. Re-source a dot file (source)
• 4. Define basic Shell Variables (PATH, SHELL,
  TERM, HOME)
• 5. Define the minimal content for the .login
  File (stty, setenv)
• 6. View Your Environment (env, stty all)
• 7. List aliases.
• 8. Temporarily disable an alias (unalias).
• 9. Change C-shell features with toggles
  (noclobber, ignoreeof, notify)

3
Customizing Your Environment

• Dot files define the environment.
• Usually in your home directory.
• The .login is executed only once at log in.
• The .cshrc is executed for each C-Shell.
• The .pinerc file defines the mail environment.
• The .forward file routes mail to another host.

4
What happens when you log in?

• You enter a login name and password.
• If the default shell is /usr/bin/tcsh, the
  T-Shell is set as your command interpreter.
• The T-Shell executes the commands in your
  /.cshrc file or /.tcshrc file.
• Then the T-Shell executes the commands in your
  /.login file.

5
Content of .cshrc

• A typical .cshrc file contains
• set path(. /bin /usr/ucb /usr/bin
  /usr/local/bin)
• set termvt100
• set history30
• set ignoreeof
• alias rm rm -i
• alias lo logout

6
Content of .login

• A typical .login file contains
• stty erase H (tset -I -Q -eH -kU)
• setenv EDITOR vi
• setenv PRINTER lw

7
Changing dot Files

• Templates are placed in new mode accounts
• Configuration changes made interactively are
  valid only for the current session.
• Changes made to .login or .cshrc are not active
  in the system until that file is "sourced"
• host source .login

8
Environment Commands

• setenv sets global environment variables
• setenv VARIABLE value
• stty sets terminal I/O characteristics
• stty option
• set defines predefined variables
• set variablevalue
• alias redefines commands
• alias name command list

9
Displaying Global Environment

• printenv displays values of global environment
  variables.
• host printenv (environment of login
  session)
• HOME/scc/users/chttspit
• SHELL/bin/csh
• TERMvt100
• USERchttspit
• PATH./scc/users/chttspit/bin/usr/ucb/usr/bin/
  usr/local/bin
• LOGNAMEchttspit
• PWD/usr/local/scc/stts
• EDITORvi

10
Display the Local Environment

• set displays C-Shell's local variables.
• host set (environment "local" to current
  shell)
• cwd /usr/local/scc/stts
• history 30
• ignoreeof (cannot use D to logout)
• noclobber (confirmation of file redirect
  overwrite)
• noglob (metacharacters ? not
  expanded)
• path (. /scc/users/chttspit/bin /usr/ucb
  /usr/bin )
• shell /bin/csh
• term vt100
• user chttspit

11
Display Terminal Characteristics

• Use stty to display terminal characteristics.
• host stty
• speed 9600 baud evenp
• erase H
• -inpck imaxbel -tab
• crt
• Special Characters
• erase H
• kill U
• intr C
• eof D

12
Displaying Aliases

• Use alias to display all aliases.
• host alias
• lo logout
• rm rm -i
• Use unalias to deactivate an alias
• host unalias rm

13
C Shell Toggles - noclobber

• Produces an error if
• redirects (gt) are made to existing files
• appends (gtgt) are made to non-existing file
• Can be used interactively with set and unset
• Can be put into .login or .cshrc
• Presence can be viewed with set command

14
C Shell Toggles

• ignoreeof -- Shell ignores EOF from terminals.
  Protects against accidentally killing a C shell
  by typing CTRL-D.
• noglob -- Inhibits filename substitution. Used
  in scripts once filenames are obtained and no
  further expansion is desired.
• notify -- Shell notifies you as jobs are
  completed, rather than waiting until a prompt.
  

15
End of Module
Complete Customizing the UNIX Environment
Exercises