Introduction to Using Computers at UTSA

The World Wide Web

If you are reading this document, then you are already somewhat aquainted with a World Wide Web browser. There are two types of Web browsers: graphical and text-based. There are many graphical browsers you may encounter; the most popular are Netscape, Mosaic, and Internet Explorer. I will refer to them all generically as Netscape, since that seems to be the one everybody uses. The text-based Web browser used on Unix systems is called lynx. Press the space bar in lynx, or use the down arrow key in Netscape, to see more of this page. You can go back up using the up-arrow in either Netscape or lynx.

The Web is a way to access information from computers all around the world using a browser like the one you're using. Certain underlined words or phrases, or pictures in the text can be selected by clicking on them using a graphical browser, or moving around with the up and down arrow keys and pressing RETURN or ENTER when the word you want is highlighted. Try that with this phrase.

Some of the text you select may show you files located on computers in other parts of the country or even other countries. If you get lost, don't panic; you can always quit using the 'q' key in lynx or choose File/Exit from the graphical browsers and then restart your session. For detailed help on using Web browsers, choose Help. In lynx, you just type 'h' for help. In Netscape, click on the word "Help" in the far upper right corner of the Netscape window. As you become more comfortable with the Web, you'll learn ways of moving around, searching for interesting information, etc.

The MS Computer Lab

The Runner System

• Find a free VT320 terminal in the lab. This is actually an art form in itself; yelling "There's free beer in the UC" might work a few times, but it is just a fact of life that there are often fewer free terminals than students needing terminals.
• Make sure the terminal is working. Some of the terminals in the lab may have been left by the previous user in a weird non-working state. Consult the helpful workers in the lab if this is the case with the only terminal you can find.
• Press RETURN a few times. You should eventually see a screen that looks something like this
  
  The Univerity of Texas at San Antonio
  Local> _
  
  with a cursor to the right of Local>. From there, type c runner and then press RETURN to connect to the runner system. You will then see something like this:
  
  Connected to runner.jpl.utsa.edu.
  UNIX(r) System V Release 4.0 (runner)
  
  
  login: _
  
  with a cursor the the right of login:. Type in the login name your teacher has given you and press RETURN. You will then be prompted for a password. Initially, your password will be your student ID number (i.e., your social security number) without dashes, e.g., 123456789. When you type in your password, you will not see it on the screen; this is so that no one can look over your shoulder and get it. The computer should immediately help you change your password (if not, see below for how to do it yourself). It will ask you to enter your old password, then enter a new password twice. The new password should be something not related to your login name and should have digits as well as alphabetic characters in it, so that it will be hard for someone else to guess and thus have unauthorized access to your account.

• man , lets you read the manual pages for Unix.
• lynx , a text-based Web browser.
• echo , a simple command that displays text on the screen
• trn , a Usenet news reader.
• Mail , an e-mail program.
• elm , an easier to use e-mail program.
• pine , another easy to use e-mail program.
• ls , a command to list your files.
• vi , an editor you can use to write programs
• cc , a compiler to translate your programs to "machine language."
• passwd , a command to change your password.

• man. This command allows you to read the manual pages for the version of Unix that runner uses, called Solaris 2.3. Simply type man followed by the name of the command you would like to know about, and the computer will display the part manual for that command. If you don't know the name of the command or are just curious about some topic pertaining to runner, type man -k followed by one or more topics you're interested in. For example, if I want to know the command for compiling a program, I type man -k compiler and the computer prints a list like this:
  
  cc cc (1b) - C compiler
  rpcgen rpcgen (1) - an RPC protocol compiler
  tic tic (1m) - terminfo compiler
  yacc yacc (1) - yet another compiler-compiler
  zic zic (1m) - time zone compiler
  
  Hmm, I don't know what all those other things are, but cc looks like what I'm interested in, so I want to see the man page for cc. I'll type man cc and get the manual page for the C compiler.

  Notice the -k I put after man. This is an option or switch to the command. Most Unix commands have options; they are described in detail in the man page for each command.

• lynx. This is the text-based Web browser described above. To use it, you can either just type lynx at the command prompt, or provide it with a URL (Uniform Resource Locator) for the file you want to start browsing, e.g. lynx http://www.utsa.edu/ for the UTSA Web page.
• echo. This simple command lets you display text on the screen. If you type echo hello and then hit RETURN, the computer will respond by printing hello on the screen. Certain special words beginning with the dollar sign are interpreted differenly by the shell. For instance, if you type echo $SHELL, the computer will show you which shell you are using. When I do this, it displays /bin/csh, indicating that I am using the C shell.
• trn. This is a newsreader. It allows you to read Usenet news, a system divided into tens of thousands of "newsgroups" contributed to by people all over the world. You can contribute to newsgroups, too, and people all around the world can read your messages. Note: newsgroups mentioned in this Web page may appear highlighted; this is because you can also read them from your Web browser by simply selecting them. However, trn is preferred by some people because it is a little more friendly environment and can be run where some Web browsers can't. The first time you enter trn, a brief section of explanatory text will appear on the screen, a special file called .newsrc will be created for you (nothing you need to think about just yet), and then you will be "in" trn. You will not see this text again unless a new version of trn is installed on runner. Once you are in trn , you will probably be presented with something like the following:
  
  Unread news in general 30 articles
  Unread news in comp.arch 22 articles
  Unread news in sci.math 290 articles
  Unread news in utsa.cs.1713-2 13 articles
  Unread news in utsa.cs.1713-3 25 articles
  etc.
  
  After this, you may see something like:
  
  Checking for new newsgroups... Newsgroup comp.new.group not in .newsrc -- subscribe? [ynYN]
  
  This means that one or more new newsgroups have become available since the last time you logged in. If you just type uppercase Y, all the new newsgroups will be added to your .newsrc, i.e., your list of subscribed newsgroups. If you don't want to see them, type uppercase N and they will be marked as unsubscribed. If you want to choose each new newsgroup individually, use lowercase instead of uppercase y or n.

  After all the nonsense is over with, you can begin reading news. First, select a newsgroup. This will be your current newsgroup . You can choose the first newsgroup in the system simply by hitting the space bar, or go to a particular newsgroup by typing g followed by the name of the group. If you're not sure of the exact name, you can search for it using the / key followed by something in the name of the group. So, you will see something like this:
  
  ====== 3 unread articles in news.announce.newusers -- read now? [+ynq] _
  
  with a cursor at the end of the line. If you wanted to go to the newsgroup utsa.cs.1713-3.d, you could type g utsa.cs.1713-3.d from there, or simply /1713 and then hit n (for next) to get to the right newsgroup.

  Once you have selected a newsgroup, you can begin reading articles by hitting the space bar. You will be presented with the first screenful of text from the article; if you want to see more of that article, hit the spacebar again. If you don't, type j (for junk), then the space bar, and you can go to the next article. Type h at any point for more details on how to use trn. To get out of trn and back into the shell, type q. You may need to type it two or three times depending on what state the newsreader is in. I suggest you try out trn for a while before reading the rest of this section.

  Let's say you have read someone's article and want to respond to it. While reading the article, type r (or R if you want to quote their article in your message) and you will be asked a few questions, then put into an editor so you can compose an e-mail message. If you would like your message to be posted to the newsgroup instead of e-mailed, use f or F instead of r. Please don't post an article to a Usenet newsgroup (except for our class newsgroup) until you have become familiar with the writing style and etiquette involved. Hang out on news.announce.newusers for a while to get an idea of what you're dealing with. Remember, if you post to a worldwide newsgroup, you are representing yourself as well as UTSA to people all around the world with different cultures and ideas.

• Mail. This is an e-mail program. You can use it to send electronic mail messages to other people. Some instructors will require you to turn in assignments through e-mail, too. Note that the first M in Mail is capitalized; make sure you type it this way when you use it on runner.

  To send someone an e-mail message, you need to know their e-mail address. This will look something like abedoya@runner.utsa.edu (this is not a real e-mail address, don't send anything to it). Type Mail -s "subject" address where subject is the subject of the e-mail, i.e., a few words describing what the e-mail is about, and address is the e-mail address. After you press RETURN, the cursor will go to the next line and you may begin typing your message. If you want to edit your message with an editor like vi, type ~v at the beginning of a new line. If you decide you don't want to send this message, press CTRL-C twice. When you are done with the message, type a single period (.) at the beginning of a new line, and your message will be sent and you will be back in the shell.

  To read your e-mail, simply type Mail in the shell. If you don't have any e-mail waiting for you, the program will let you know. Otherwise, you will enter an interactive shell-like environment where you can read e-mail message and respond to them. For instance, if I type Mail from my Unix prompt, I will see the following:
  
  mailx version 5.0 Wed Oct 25 04:12:43 PDT 1995 Type ? for help.
  "/var/mail/djimenez": 1 messages 1 new 2 unread
  >N 1 Daniel Jimenez Fri Feb 30 17:31 15/366 stuff
  
  
  This indicates that I have a single e-mail message from Daniel Jimenez (yes, I sent myself an e-mail message) with subject "stuff." From here I can type RETURN to see the message, or type q to quit and save the message in a file of already-read e-mail message, or just type x to quit and leave my mailbox in the same state it was before I entered Mail.

• elm. This is a full-screen e-mail program, i.e., it lets you navigate through your e-mail and send other people message by choosing items from a menu. It is somewhat like lynx, except it's just for e-mail. Read the man page for elm for more details (real programmers use Mail).
• pine. This is another full-screen e-mail program like elm . Many people at UTSA like it for its ability to send attachments and graphics (although it is a text-based program). Again, real programmers use Mail, pine is for sissies :-) (that :-) is a "smiley" and means a happy face, a joke, ha ha, not being serious, and so forth).
• ls. This command allows you to see information about the files in a directory . A directory is a place where you can hold some of your files. You have a main directory that you are "in" when you first log in, and you can make other directories to store related files if you like. ls will show you the names of the files in your directory. If you type ls -l, you will see the names in a long format showing the size, creation date, and other information about the files. See the man page for ls for a description of all the options to ls.
• vi. This is a popular editor that works on all Unix systems. An editor allows you to enter, edit, and save text files, such as computer program source code. It is somewhat similar to a stripped-down word processor. There are other editors available under Unix, but vi is the most widely available.

  To edit a file, enter vi followed by the name of the file. If the file doesn't yet exist, you will be presented with a "blank" screen with tildes (~) running down the left side of the screen. Otherwise, you will see the contents of the file, possibly followed by tildes marking the end of the file. vi allows the user to type commands using a few keystrokes. It can be faster than using a word processor, but can be challenging to learn at first. Refer to a Unix book for more information about vi commands; a few basic commands are presented here. vi has two modes , command mode and insert mode. In command mode, anything you type is interpreted by vi as a command to the editor to do something. For instance, in command mode, typing the sequence :wq tells the editor to Write (i.e., save) the current file, then Quit back into the shell (or whatever other program invoked vi). In insert mode, anything you type is echoed to the screen and becomes part of the file you are editing, just like in a word processor. Press ESC (or CTRL-[ on terminals without an ESC key) to return to command mode from insert mode. If you're not sure what mode you're in, press ESC a couple of times until you hear a beep; then you know your in command mode. Most commands can be aborted in the middle by pressing ESC. Many of the following commands are described in terms of the current position; this is, depending on the context, the character or line occupied by the cursor. Here are a few common commands; remember, they are case-sensitive and must be entered from command mode:

  • i Enter insert mode, inserting text before the character at the cursor position.
  • a Enter insert mode, inserting text after the character at the cursor position.
  • I Enter insert mode, inserting text at the beginning of the current line.
  • A Enter insert mode, inserting text at the end of the current line, i.e., appending text to the current line.
  • j Go down one line.
  • k Go up one line.
  • l Go one space to the right.
  • h Go one space to the left.
  • o Open a new line after the current line, i.e., insert an empty line between the current and next line, remaining in insert mode.
  • x Delete the current character (like the DEL key in a word processor).
  • X Delete the character to the left of the current character (like the BACKSPACE key in a word processor).
  • dd Delete the current line.
  • dnd Delete n lines from the current cursor position, for example, d10d to delete ten lines. Note: some versions of vi won't display the characters of the commands as you are typing them, so make sure you type d10d instead of, say, d100d.
  • u Undo the last command. This is useful if you just deleted something you didn't mean to delete, or inserted something you didn't mean to insert.
  • p Paste the last section of deleted text after the current line. You can do "cut and paste" in vi by going to the section you want to cut, deleting it, going where you want to paste, and using the p command. You can type p as many times as you want, inserting another copy of the last text deleted each time.
  • :w Save the current file and continue editing. Note: many vi commands begin with a colon (:). You will see these commands displayed at the bottom of the screen because many of them take parameters you need to be able to see to type.
  • :wfilename Save the current file to a different filename.
  • :q Quit the editor. If you have made modifications to the text, vi won't let you quit like this.
  • :q! Really quit the editor, abandoning all changes you have made during this session.
  • :rfilename Read the contents of the named file into the editor at the current position.
  • :sh Start a Unix shell. Typing exit from the shell will return you to the vi session from which it was started.
  • :!command Execute the specified Unix command, returning to vi when it is done.
  This is just a small sample of vi commands, but it is enough to start you editing your own text files.
• cc . This is the command to invoke the C compiler. You give it command-line parameters that specify one or more source files and it produces an executable program (or linkable object file, depending on on parameters). For instance, the command cc foo.c compiles the program in the text file foo.c (created with vi or some other editor) and produces an executable file called a.out. You can then execute a.out if the compilation succeeded, or read the error messages if it failed. Normally, you will want to name your executable something other than a.out, so use the -o option to cc, e.g., cc -o foo foo.c will compile foo.c and call the resulting executable foo. Note: If you get the order wrong on a command like the previous one, say, cc -o foo.c foo, cc will probably overwrite your source file, thinking that that's what you want to name your binary. Be careful you don't do this. See the man page for cc for more information on the options.
• passwd . This command allows you to change your password. On many Unix systems, including runner, a password must be reasonably secure in the sense that it is hard to guess. You must have at least six characters in your password, and some of them must be digits or special characters. Two short unrelated words separated by a special character or digit is usually both secure and easy to remember. Examples of good passwords: djgh12xz, cat.mart. Examples of bad passwords: your login name backwards (or forwards!), your birthdate, your girlfriend's/boyfriend's/wife's/husband's/kids' etc. names, any single word in any language (including German, Spanish, Hebrew, French, Mandarin, Swahili, Telugu, you name it, people out there will try to guess it). To use passwd, just enter the command. You will be prompted for your old password (to make sure it is really you), then twice for a new password. The second time is to verify you typed the same thing both times.