June 1, 1999 Customizing the UNIX Environment 1

Introduction to UNIX

G. Customizing the UNIX Environment

June 1, 1999 Customizing the UNIX Environment 2

Customizing the UNIX Environment

Performance Objectives1. 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)

June 1, 1999 Customizing the UNIX Environment 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.

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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.

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Content of .cshrc

• A typical .cshrc file contains: set path=(. ~/bin /usr/ucb /usr/bin /usr/local/bin) set term=vt100 set history=30 set ignoreeof alias rm rm -i alias lo logout

June 1, 1999 Customizing the UNIX Environment 6

Content of .login

• A typical .login file contains: stty erase ^H (tset -I -Q -e^H -k^U) setenv EDITOR vi setenv PRINTER lw

June 1, 1999 Customizing the UNIX Environment 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

June 1, 1999 Customizing the UNIX Environment 8

Environment Commands

• setenv sets global environment variables: setenv VARIABLE value

• stty sets terminal I/O characteristics: stty option

• set defines predefined variables: set variable=value

• alias redefines commands: alias name “command list”

June 1, 1999 Customizing the UNIX Environment 9

Displaying Global Environment

• printenv displays values of global environment variables.

host% printenv (environment of login session)HOME=/scc/users/chttspitSHELL=/bin/cshTERM=vt100USER=chttspitPATH=.:/scc/users/chttspit/bin:/usr/ucb:/usr/bin:/usr/local/binLOGNAME=chttspitPWD=/usr/local/scc/sttsEDITOR=vi

June 1, 1999 Customizing the UNIX Environment 10

Display the Local Environment

• set displays C-Shell's local variables.host% set (environment "local" to current shell)cwd /usr/local/scc/sttshistory 30ignoreeof (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/cshterm vt100user chttspit

June 1, 1999 Customizing the UNIX Environment 11

Display Terminal Characteristics

• Use stty to display terminal characteristics.host% sttyspeed 9600 baud; evenperase = ^H-inpck imaxbel -tabcrtSpecial Characters

erase ^Hkill ^Uintr ^Ceof ^D

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Displaying Aliases

• Use alias to display all aliases.host% alias

lo logout

rm rm -i

• Use unalias to deactivate an alias:host% unalias rm

June 1, 1999 Customizing the UNIX Environment 13

C Shell Toggles - noclobber

• Produces an error if redirects (>) are made to existing files appends (>>) 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

June 1, 1999 Customizing the UNIX Environment 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.

June 1, 1999 Customizing the UNIX Environment 15

End of Module

Complete Customizing the UNIX Environment Exercises