.SH "Getting your login name" You will be given your login name during a lecture. The reason you all have different login names is so that you can be working on something of your own, which nobody else can alter. You have a completely different environment from everybody else, which means that other users cannot know exactly what you are doing (unless they look over your shoulder). Although the resources on a computer are large they are not infinite, and hence restrictions are placed on every user so that the resources are not depleted or congested. These restrictions apply to such things as the amount of space you can use on disk, and the number of processes you can have going at any one time. .H 2 "Logging In" The first thing to do if you want to log in is find a terminal that is apparently not being used. The next thing to do is to ensure that the terminal is turned on. If it is not turned on, turn it on and wait till the cursor\*F appears, .FS only on video or graphics terminals. .FE then hit <return>\*F .FS <return> denotes the 'carriage return' key on the keyboard. It is marked as 'RETURN' or 'CR'. The <return> is .ul very important as the system will not obey you until you type <return>. This applies in all situations. .FE until the system responds. If you are on a Tektronix terminal remember to clear the screen (see section 1.4). After hitting <return> the system will respond .DS login: .DE if nobody is using the terminal. If this line does not appear then you must either wait or find another terminal. .P When you have found a terminal with .DS login: .DE displayed, just type in your login name followed by <return>. If the system responds with .DS Who? login: .DE it means that either you typed in your login name incorrectly or your login name is not known by the machine. If this happens keep trying until you get a successful login, but if it continues to happen then consult the school's computer personnel. Upon successful login the system will respond .DS password: .DE .P The machine is now waiting for you to type in your password. Anybody can find out your login name, so, in order to protect the privacy of your files, you have a password. When typing your password you will notice that the letters are not printed on the terminal. This is to preserve the secrecy of your password. .P You can change your password and it is strongly suggested that you do so regularly; using one of at least eight letters. Changing your password will be explained latter, in the section "Common Commands". .P If you type in the wrong password the terminal will respond with .DS Wrong Password login: .DE and you have to start again with your login name. If you have correctly typed in your password then the terminal might respond .DS 1 ~~~~~~System down twixt 17:00 and 21:00 tonite~~~~~~~~~~~<-- 1 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ianj ~~~~~~100 disk units~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<-- 2 ~~~~~~~~4 processes You have mail~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<-- 3 %~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~<-- 4 .DE .P Message #1 is called the message of the day, and is used by the system supervisor to tell users of forthcoming events, or just general information. In this case it is a rather cryptic message saying that the machine will be unavailable for use between 17:00 and 21:00 that night. Don't be scared off by bad spelling or jargon words as they are only used to keep the message short. If you can't understand this message there are plenty of people around to ask. It is suggested that you take note of this message as it may cause you some inconvenience if you don't. .P Message #2 tells you of the resources at your disposal. These will be explained in greater detail later. .P Message #3 tells you that you have mail. As in the outside world, users of this system can send each other mail. This is a convenience so that users can communicate without ever seeing each other. .P The last message (the percent sign %) is a way of telling you that the system is ready to take commands. This is usually called "the prompt". The percent sign is printed by a program called the "shell". The shell is executed when you log on and reads the commands you type in. It then performs the necessary actions to execute the program. It should be noticed that the shell does not care whether your command makes sense. It merely passes your command to the particular program that command uses. .P Once all of this has happened you are logged on to the machine and are able to use its facilities. .H 2 "Logging Off" Logging off terminates your session with the computer. If you don't log off, the system will automatically log you off after ten minutes have passed since the last command was completed\*F. .FS this should not be construed as an invitation to log off this way. It only takes a few seconds for another user to (intentionally or not) destroy all your files which may have taken months to prepare. .FE This is for your benefit and for the protection of your files as it prevents misuse of your account if you leave the terminal for a long time. .P To log off you type .DS [control]d .DE ie. you hold down the control key and type a 'd'. The control key (sometimes labelled 'ctrl') is similar in operation to the shift key. .H 2 "Line Editing" Line editing is a way of correcting typing errors in a line before the system reads them. The system accepts each line only after you have typed <return>. .P If you happen to make a mistake typing anything in, there are two ways to fix the error. .P The first method of deleting errors is to use the '#' character. This character, when typed after any other character, will delete it from the line. Thus several '#'s in a row will delete that many characters back. For example, the following .DS I are##m a fppl###oo;#l .DE will be read by the system as .DS I am a fool .DE .P To enter the character '#' you type '\\#'. The '\\' (slosh) removes the special meaning of '#'. .P As you can see in the above example, using '#' to erase characters is quite messy, making the line rather hard to read on first glance. If you are using a video terminal (a terminal with a screen) you can use a backspace key instead, so that when you make a mistake in typing you can simply use the backspace key to correct the errors, and then continue typing. To change the erase character to a backspace you must type .DS % set % .DE After typing in 'set', experiment with using the backspace key to erase characters. As you backspace over the characters they will disappear, indicating that they have been deleted. .P If you are on a DECwriter terminal, typing 'set' will not cause the erase character to be changed. This is because it is not considered useful as the terminal will only overprint the characters. If you are on a tektronix terminal and you type in 'set', you may find it difficult to find the backspace key. In fact it doesn't have one! You must use [control]h. ([control]h is the character sent to the computer by the backspace key). .P The second form of "line editing" is the '@' sign. When '@' is typed, all of the characters typed on the line so far will be erased. If you type an '@' in error, it may be erased (like other characters) by a '#' (or a backspace as the case may be). For example, the following .DS I qte@I arm not sil@I am no fool .DE will be read be the system as .DS I am no fool .DE .H 2 "Reading Your Mail" To read your mail type .DS % mail .DE and the following may appear .DS From root Fri Nov 13:05:44 Welcome to UNIX and AGSM We hope your stay here is enjoyable Save? .DE .P The computer is now waiting for you to type .DS yes OR no .DE depending on whether or not you want to save the mail. If you save your mail it is added to a file called "mbox". .P If you wish to send mail to another user whose login name is 'joe' (say), you type .DS % mail joe .DE Once you have done this the system is waiting for you to type in the mail. You might like to type .DS I've finally arrived...... Must talk with you about that discussion we were having. Jack .DE When you have finished your mail you must now type .DS [control]d .DE ie. hold down the control key and type a 'd'. When 'joe' logs on next he will be told that he has mail, and when he reads his mail the date and your login name will appear on the front of the mail sent by you. .H 2 "Error Handling" From time to time unexpected messages will appear on the terminal probably informing you that an error has occured. Ignore these messages at your own peril! Don't be tempted to sit there like a stunned mullet; go and ask somebody what the message(s) mean. It has been distressingly observed in the past that people have seen an error message, ignored it, and then found out two days later that the work they had been typing in was lost forever. It is very frustrating for the computer personnel who are asked to fix up such problems, when told they occured days earlier, and could have been avoided. It is also frustrating for you as it may be too late to do anything! Hence it is very important that you don't ignore potential error messages. .P If you are not sure what the error is or what caused it, ask somebody. Most errors can be corrected by any user familiar with the system. For the rest, contact the system staff (in this case write the error message down). Lost files can normally be recovered. In this case, the system staff .ul must be informed and given the name of the file and the date that it was last changed (not used, but altered)\*F. .FS if you cannot notify them personally, use the mail command viz "mail root". .FE .H 2 "Stopping Programs" If at any stage you wish to stop a program you hit the delete key (labelled "del" or "rubout"). Some programs, like the editor, will not stop execution when you hit this key but, instead, return control to you. .H 2 "System Crashes" From time to time the "system crashes". This means that the system (which is just a program) has either developed a fault, or it has found a fault in the computer (usually temporary). When the system crashes nobody can use it, it will become lifeless. No characters will be printed on terminals, all programs will stop. During violent thunder storms the system will be stopped to prevent any damage to the computer and related hardware. If the system crashes while you were in the editor, all information after the last write will be lost (the editor is explained in later sections). In some rare circumstances you will be able to recover the lost information. If this happens you should try and find the system staff who will normally be in Rm 411 recovering the system.