Section I.

                           INTRODUCTION TO UNIX

                          Advanced Unix Concepts

       On Unix systems there is a special user called root (also known as
       the super user or privileged user) who has complete control over
       all processes and files/directories, regardless of permissions or
       ownership.  Only root may use many system commands, especially
       those that change the configuration of the system.

                         Environmental Variables

       You may easily customize your environment by setting variables to
       specific values to suit your needs; most are pre-defined for you
       by the system administrator but can be changed.  Depending on
       which command interpreter (shell) has been defined for you,
       variables are set in configuration files that reside in your home
       directory.  The Bourne shell executes commands and sets variables
       defined in the .profile file, while the C-shell first executes the
       .login file, then the .cshrc file.  The .cshrc file is also
       executed every time the csh command is executed on the command
       line.  When you log off using the C-shell, the commands found in
       the .logout file are executed.

       *** Note ***  Be extremely cautious modifying configuration files;
                     it is advisable to first copy the file to a backup

       Some useful commands which can be included in your .configuration
       file(s) are:

       alias - if you put a line in your .cshrc file like:

               alias lo logout

               you can then enter lo which the shell will expand to
               logout.  This is particularly useful for long, complicated

       history - a line containing:

                 set history=100

                will cause the shell to store up to the last 100
                commands.  To display the history list, enter:

                % history

                at the command prompt and the history list will be
                displayed.  To re-execute the 13th command, enter:

                % !13

                To save the history list as a log of your activities, add
                the line:

                history >>~/history.log

                to your .logout file.

       prompt - setting this variable, your prompt can look like whatever
                you choose.

       stty - stty commands can be used to change the value of terminal
              configuration variables (see man pages).

       There are many commands which display information, or do specific
       tasks to help you manage your environment.  Some useful commands

     passwd - changes your password
         ps - displays processes and status
       kill - used to terminate a locked process
      quota - reports current disk usage and limits
       find - searches the filesystems for files/directories
         df - reports filesystems currently mounted and disk usage
          w - reports who is logged on the system

       *** Note ***

       1) see the on-line man pages for syntax of specific commands
       2) see Unix Command Summary for other useful commands

       One of the great advantages of Unix is the ability to run commands
       detached from the terminal you are using.  To run a process in the
       background, simply append an & (ampersand) to the end of the line.


       % ls -lR / >~/all.files &

       causes a long, recursive listing of the entire filesystem, putting
       the output into a file called all.files in your home directory,
       running detached from your terminal.

       To display the status of any such jobs, enter the command:

       % jobs

       With three processes running in the background, to bring job 2 to
       the foreground, enter:

       % fg %2

       To move a command running in the foreground to the background,

       % ^Z

       to stop the job, then

       % bg

       Note: Not all shells support job control.

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