Computers: Universe: The Command Prompt

If you have not yet created a Universe account, do: see Universe and UNIX above.

If you have, cd to the directory housing the account, and start Universe.

The command to start Universe account is uv. The UniVerse bin directory contains this executable: if it is not on your path, you will have to enter the full path: it will be something like /universe/bin/uv.

This will bring you to the Universe prompt:

>

At this prompt, you can enter commands. The following commands are worth learning first:

QUIT

Before you learn anything else, learn how to get back to UNIX from UniVerse: simply enter QUIT. Some people find themselves logged off their server on entering QUIT, but this is not because the command itself logs you off. It only happens where a friendly system administrator has devised a command file which first invokes UniVerse and then logs out. It means that while you are in UniVerse, the UNIX command file is still running: and as soon as you return to UNIX it completes by logging you off.

LO

Unless you are using a system which logs you out when you type QUIT (see above), QUIT will only return you to UNIX. If you plan to log off the system entirely, you can do so directly from UniVerse by entering LO.

SH

This command has already been mentioned (see UniVerse and Unix above). It merely suspends UniVerse and opens a UNIX shell. It is bad practise to log out of this shell, as it doesn't give UniVerse a chance to 'shut down' tidily (releasing locks, clearing file I/O buffers and so on): always exit back to UniVerse first. Within the shell, you can carry out most UNIX functions, though you should not recursively start UniVerse again, and you should bear in mind that even if you use cd to move to a different directory, on leaving the shell you will be returned to your original UNIX directory and your original UniVerse account.

LOGTO

LOGTO takes the place of UNIX's cd command in that it moves you from one UniVerse account to another, in much the way that cd moves you from one UNIX directory to another.

However, it works slightly differently in that it doesn't accept pathnames to indicate your destination: the syntax is simply LOGTO accountname. This is because, as was explained during the description of UniVerse's heirarchical structure (see The UniVerse Paradigm above), UniVerse accounts are not recursive: that is to say, as far as UniVerse is concerned, no account contains another account. UniVerse keeps a single central list of all the accounts on a system, and when you specify the account name you wish to go to, it finds the UNIX path from this list. Even if one UniVerse account has been created in a subdirectory of another (note: not good practice), UniVerse does not recognise any relationship between them, merely two accounts at different paths.

Here lies one of the examples of something I mentioned earlier: the risks of applying UNIX commands to UniVerse structures (see UniVerse and UNIX above). If you move a directory containing a UniVerse account using the UNIX mv command, all may seem well. If you cd to the new pathname and invoke UniVerse, it will work. However, if you try to LOGTO the account you moved from UniVerse, the command will fail. This is because UNIX is not aware of UniVerse's internal controls, and will not update it's internal list of account locations. This, you must do yourself using the UNIX Administrator's menu, which is unfortunately outside the scope of this document. Refer to the UniVerse documentation for more information on this point.

SET.TERM.TYPE

Each different kind of dumb terminal has it's own instruction set for doing things like displaying text at particular screen locations, or displaying text in bold, and so on. In order to cope with these, UniVerse must know which kind of terminal you are using. If, as is now increasingly likely, you are using a PC based terminal emulator, it must know which kind of terminal it is emulating.

To set the terminal type, you can enter SET.TERM.TYPE, and enter a ? when asked for your terminal type. UniVerse will then display a list of those it supports. Select your terminal from this list.

It would be a good idea to do this before trying any of the examples in the remainder of this course: they all assume that your terminal type has been set up correctly. This terminal type definition lasts until you leave UniVerse: when you return to UniVerse you will have to use this command again, though there are ways to automate 'start up' commands of this kind, as you will learn later.

HELP

UniVerse boasts an extremely comprehensive on-line help system, similar to the UNIX man facility. To get information about a command, enter HELP commandname. For instance, you could enter HELP LOGTO to read about the LOGTO command, or even the rather desperate sounding HELP HELP to learn about the help system itself. This on-line manual also covers the statements in the UniVerse Basic programming language: a point we shall return to when the language is discussed later.

DISPLAY

To display something on the screen, enter the command DISPLAY string, as in DISPLAY Hello Mum!. This a useful enough command, but not tremendously important: I explain it because I will be asking you to enter it later as part of some worked examples on other subjects.