---

Logging On To The System

• Before you can begin to use the system you will need to have a valid username and a password. Assignment of usernames and initial passwords is typically handled by the System Administrator or a "Computer Accounts" office.

• Your username, also called a userid, should be unique and should not change. Initial passwords can be anything and should be changed after your first login.

• To login to your account
  1. Type your username at the login prompt. UNIX is case sensitive - if your username is kellyk do not type KellyK . Press the RETURN or ENTER key after typing your username.

  2. When the password prompt appears, type in your password. Your password is never displayed on the screen as a security measure. It also is case sensitive. Press the RETURN or ENTER key after entering your password.

• What happens after you successfully login depends upon your system:

  • Many UNIX systems will display a login banner or "message of the day". Make a habit of reading this since it may contain important information about the system.

  • Other UNIX systems will automatically configure your environment and open one or more windows for you to do work in.

  • You should see a prompt - usually a percent sign (%) or dollar sign ($). This is called the "shell prompt" (the shell is discussed in detail later). It indicates that the system is ready to accept commands from you.

• If your login attempt was unsuccessful, there are several possible reasons:
  1. You made a typing error while entering your username or password

  2. The CAPS LOCK key is on and everything is being sent to the system in uppercase letters.

  3. You have an expired or invalid username or password, or the system security has changed.

  4. There are system problems

• Example

  
  login: kellyk
  kellyk's Password: 
  ************************************************************
  * Welcome to the Maui High Performance Computing Center
  ************************************************************
  *
  * Aloha no! (Greetings)
  *
  * System maintenance is scheduled today from 2:00 
  * until 4:00 pm HST
  *
  *                     Mahalo nui loa (Thank you very much)
  *
  ************************************************************
  
  %
  

• Begin the "Logging On To The System" Exercise

Your Home Directory

• Each user has a unique "home" directory. Your home directory is that part of the file system reserved for your files.

• After login, you are "put" into your home directory automatically. This is where you start your work.

• You are in control of your home directory and the files which reside there. You are also in control of the file access permissions (discussed later) to the files in your home directory. Generally, you alone should be able to create/delete/modify files in your home directory. Others may have permission to read or execute your files as you determine.

• In most UNIX systems, you can "move around" or navigate to other parts of the file system outside of your home directory. This depends upon how the file permissions have been set by others and/or the System Administrator, however.

Using UNIX Commands

• UNIX commands are executable files and built-in utility programs

• All UNIX commands are case sensitive. Most commands are in lower case.

• Commands typically have the syntax:

   
       command  option(s)   argument(s) 
       

• Options
  1. Modify the way that a command works
  2. Usually consist of a hyphen followed by a single letter
  3. Some commands accept multiple options which can usually be grouped together after a single hyphen
  4. A small number of commands require each option to be given separately
  5. Should be separated from the command name by a space

• Arguments
  1. Most commands are used together with one or more arguments
  2. Some commands assume a default argument if none is supplied
  3. Arguments are optional for some commands and required by others
  4. In most cases, multiple arguments should be separated from each other by a space. They should be separated from the command name and/or options by a space also.

• Examples

  1. To use a command with no argument: the "date" command displays the current time and date.

          date 

  2. To use a command with a single argument: the "cd" command changes to the directory of its argument, newdir

          cd newdir 

  3. To use a command with both an option and an argument: the wc command counts the number of words, characters, and lines in a file. By using a different option you can choose what is counted.

     
          wc -w file1     counts the words in file1 
          wc -c file1     counts the characters in file1 
          wc -l file1     counts the lines in file1 
               

  4. To use a command with several arguments: the cat command takes the names of three files as arguments. It prints file1 followed by file2 and then file3 on the screen.

          cat file1 file2 file3 

  5. To use a command with multiple options and default argument: the ls command provides a long (l) listing of all (a) files and also shows the file size (s). Because no argument is specified, the default argument (current directory) will be used.

          ls -als 

• Multiple commands can be entered on one line if you separate each with a semicolon. For example: this command line contains two commands. The first, cd newdir changes the current directory to the directory newdir. The second, ls -l produces a long listing of the contents of the newdir directory.

       cd newdir ; ls -l  

• Commands can continue beyond one line by using a backslash (\) character. For example: this command copies the file called recipe from kelly's home directory to the current directory and renames it kelly.recipe. It then sends this file to the printer ps3 with the request that 6 copies be printed.

  
       cp /users/kelly/recipe  kelly.recipe ; \  
       lpr -Pps3 #6m kelly.recipe
       

• Begin the "Using UNIX Commands" Exercise

Special Characters

• The UNIX shell interprets a number of characters in special ways. These characters are most often used with UNIX commands - as arguments and for other means. The following list contains most of UNIX's special characters

  
       NEWLINE   - initiates command execution 
       ;         - separates commands on same line 
       ( )       - groups commands or identifies a function 
       &         - executes a command in the background 
       |         - pipe 
       >         - redirects standard output 
       >>        - appends standard output 
       <         - redirects standard input 
       *         - wildcard for any number of characters in a 
                   file name 
       ?         - wildcard for a single character in a file 
                   name 
       \         - quotes the following character 
       '         - quotes a string preventing all substitutions 
       "         - quotes a string allowing variable and 
                   command substitution 
       `         - performs command substitution 
       [ ]       - denotes a character class in a file name 
       $         - references a variable 
       { }       - command grouping within a function 
       .         - executes a command (if at beginning of line) 
       #         - begins a comment 
       :         - null command 
       

• Examples

  1. Use the * character in file names to match any number of characters. The following command:

          ls  *.txt 

     Will match the following files:

          chapter1.txt   doc.txt  memo.txt  a.txt 

     Will not match the following files:

          doctxt   txt.memo  

  2. Use the ? character in file names to match any single character. The following command:

          ls  ???.txt 

     Will match the following files:

          one.txt   doc.txt  two.txt 

     Will not match the following files:

          chap1.txt   doctxt  

  3. Use the [ ] characters in file names to match any character within a range of characters. The following command:

          ls  chapter[1-3].txt 

     Will match the following files:

          chapter1.txt   chapter2.txt  chapter3.txt 

     Will not match the following files:

          chap1.txt   chapter4.txt  

• Other uses for special characters and examples will be discussed later.

• Begin the "Special Characters" Exercise

Terminal Control Keys

• Several key combinations on your keyboard usually have a special effect on the terminal.

• These "control" (CTRL) keys are accomplished by holding the CTRL key while typing the second key. For example, CTRL-c means to hold the CTRL key while you type the letter "c".

• The most common control keys are listed below:

  
       CTRL-u   - erase everything you've typed on the command 
                  line 
  
       CTRL-c   - stop/kill a command 
  
       CTRL-h   - backspace (usually) 
  
       CTRL-z   - suspend a command 
  
       CTRL-s   - stop the screen from scrolling 
  
       CTRL-q   - continue scrolling 
  
       CTRL-d   - exit from an interactive program (signals end 
                  of data) 
       

• Begin the "Terminal Control Keys" Exercise

Changing Your Password

• Your password is important; it stops other users from gaining access to your account. Never give your password to anyone

• You should change your initial password very soon after your first login

• To change your password: enter the command passwd and then respond to the prompts by entering your old password followed by your new one. You are then asked to retype your password for confirmation.

  Note that what you type will not appear on the screen for security reasons. For example:

  
       passwd  
       Old password: - enter your current password 
       New password: - enter your new password 
       Retype new password: - re-enter your new password 
       

  If you make a mistake, the message: Mismatch - password unchanged. is displayed and your password remains unchanged. Try again.

• Guidelines for creating a password

  Don't

  • choose a word from a dictionary
  • use personal information such as your name, make of car, pet, sweetheart, etc.
  • tell anyone your passwd
  • write your password down anywhere
  • keep the password you were given when you first got your userid

  Do

  • choose an obscure password preferably between 6 and 8 characters in length, of mixed case and containing at least one non-alphanumeric character such as ! or @
  • change your password at regular intervals

• Keep in mind that there are people who think it's fun to "crack" passwords and get into other people's accounts. There are plenty of easily available "cracking" programs which make guessing easy passwords a cinch.

• Begin the "Changing Your Password" Exercise

Getting Information

• The "man" command

  • The "man" command man gives you access to an on-line manual which potentially contains a complete description of every command available on the system. In practice, the manual usually contains a subset of all commands.

  • man can also provide you with one line descriptions of commands which match a specified keyword

  • The online manual is divided into sections:

    
         Section  Description
         -------  -----------
            1     User Commands
            2     System Commands
            3     Subroutines
            4     Devices
            5     File Formats
            6     Games
            7     Miscellaneous
            8     System Administration
            l     Local Commands
            n     New Commands
         

  • Examples of using the man command:

    1. To display the manual page for the cp (copy files) command:

            man cp

       --More--23% at the bottom left of the screen means that only 23% of the man page is displayed. Press the space bar to display more of it or type q to quit.

    2. By default, the man page in section 1 is displayed if multiple sections exist. You can access a different section by specifying the section. For example:

            man 8 telnetd 

    3. Keyword searching: use the -k option followed by the keyword. Two examples appear below.

            
            man -k mail 
            man -k 'copy files' 
                      

    4. To view a one line description of what a command does:

            whatis more

       will display what the "more" command does:

       more, page (1) - browse or page through a text file

• who - shows who is on the system

  
       who
       who am i
       

• finger - displays information about users, by name or login name

  
       finger doe 
       finger userid 
       

• Begin the "Getting Information" Exercise

Logging Off The System

• To finish using a UNIX system you must go through a process known as "logging out" or "logging off".

• To logout enter the command logout or exit. If this does not, work press Ctrl-d.

• If you have a .logout file in your home directory, the system will execute any commands contained there.

• Problems

  1. If you see the message There are stopped jobs it is a warning which tells you that there is a job which you suspended earlier (Ctrl-z) or a job running in the background (discussed later).

     The simplest way to accomplish the logout is to just issue the logout command again. Your suspended/background jobs will be terminated and you will be logged off the system.

  2. If you see the message Not login shell it means you are working in another "shell" that has been started from within your "login shell" (shells will be discussed later).

     To logout, issue the exit command and then try to logout again.

• Begin the "Logging Off the System" Exercise

This concludes the tutorial. Return to the Table of Contents