Sooner or later you'll need to use Unix to run advanced programs. The
favorite editor to use in conjunction with Unix is Emacs, so you might
want to get familiar with Emacs basics too. There is also the "pico"
editor available which is much simpler to use and all you need for
assignment 3.
Getting Started
There several ways to access Unix machines in the SIMS environment.
(We will be using Solaris Unix, because that is the Unix that runs on the
Sun machines that we use in the lab. FYI, Linux is
an increasingly popular form of Unix and we might have this in the lab in
future. The differences between these are supposed to be unnoticable, so
you don't really need to worry about this.)
For the work in this course the following method of accessing Unix
should work fine. On an NT machine, access the SecureCRT program at
Start\Programs\Internet\SSH-Telnet\SSH-info.sims
(You shouldn't use irony.sims for this assignment, as it is used for
other purposes. This is the secure version of telnet we're supposed
to use now. It encrypts your password over the network for you.)
You'll get some dialog boxes the first time you run this. Go ahead
and make it your default telnet application in the first dialog box, and
select Accept & Save in the second box. After this first time you won't have
to repeat all these commands.
Once you're past all the dialog boxes, you'll get a prompt TERM =
(xterm). Just hit Return when you see this. Now you're logged into a
unix machine (called info.sims).
This is a very nice version of telnet. You'll notice the command menu
at the top allows you to do cut and paste, change the keyboard mapping,
and many other things.
Learn Unix
Read the information on Basic UNIX File Manipulation at
http://socrates.berkeley.edu/Help/Unix/basicunix.html Now do
the following operations (after each task I show the appropriate unix
command in italics).
- Create a new directory called stuff
- mkdir stuff
- Make stuff your current directory
- cd stuff
- Print the current directory
- pwd
- Create a new file called greeting containing the word "hello"
- echo "hello" > greeting
- Look at the contents of the file called greeting
- more greeting
- Copy this file to another file called greeting2
- cp greeting greeting2
- Remove the first file
- rm greeting
- Move up out of this directory to your home directory
- cd ..
- Check that you're really in your home directory
- pwd
- Look at the files in this directory in more detail
- ls -l
Unix has online manual pages, called man (everything gets abbreviated,
in case you haven't noticed, to reduce typing).
- Try out the man command at the Unix prompt.
- See what that more command was we used earlier.
- man more
- (The stuff under Synopsis indicates the different arguments
that you can give to different variants of the command.)
- Find out how to make ls show you files whose names begin
with a . (a period).
- man ls
More info on
man pages.
Now read about
running
jobs and processes,
redirecting input and output,
connecting commands together, and
using wildcard characters.
If you'd like more references, there is a list of recommended Unix guides at
http://wss-www.berkeley.edu/unix/faq/books.html
Learn Emacs
Now learn some basics about the emacs editor. Emacs has a huge range of
functionality but you only need to know the basics to get started.
(Its name stands for Easy Macros.)
Emacs makes extensive use of the Control key, which can take getting
used to. Something written as C-x C-c means first hold down the
control key and press x (while still holding down the control key) and
then do the same thing with control and c. (You can keep the control
key held down for both the x and the c.)
You can run emacs from the Unix prompt by simply typing Emacs.
This puts you in a buffer called *scratch*, which is temporary scratch space.
You save a buffer's contents into a file by typing C-x C-s.
You can get out of emacs by typing C-x C-c.
Undo the previous command with C-x u
(This means hold down control and x at the same time, then release
the control key and hit the u.)
The Meta key (usage is written M-x, for example) is either the Alt key
or the ESC key; you'll have to test it out on your system.
First read an emacs tutorial, for example
http://yoda.cis.temple.edu:8080/UGAIWWW/help/emacs-tutorial.html
Now use tutorial materials prepared by Armando Fox.
Go back to the unix prompt and do the following commands.
- Go to your home directory.
- Make a directory called emacs-tutorial
- Copy the files from the directory /www/docs/courses/is202/f00/emacs-tutorial
into your emacs-tutorial directory.
- Move into your emacs-tutorial directory.
- Check that it is really your directory (use pwd).
- Now read the contents of the file called README (use the more command)
and follow the instructions there for how to run the emacs tutorial.
Especially Useful Emacs Commands
Below I list what I consider to be especially useful emacs commands, omitting
emacs macros, which get their own section, below.
- Search in the buffer. After you type the command, start typing in
the letters of the string you are searching for. After you find the first
hit on the string, you can type the command again and get the next and
subsequent hits. When you get to the end of the file, the search begins again
from the top of the file.
- C-s
- Replace string. I use this every day. It lets you replace one
string of characters with another in the current buffer. After you
type the command you enter a dialog with the system and it asks you
what pattern you want to replace with what other pattern.
- M-x replace-string
- Query replace. I also use this every day. It's like
replace-string except it pauses before each replacement and asks you
if you want to replace that particular instance of the string. This
is useful because sometimes it's hard to specify exactly the pattern
you want to replace. If you want to replace the string you hit
Return, otherwise you hit "n" (for no).
- M-x query-replace
- Help: This gets you into the comprehensive online help facility.
Here is a nice webified description of the help options.
- C-h ?
Emacs Macros
There are some aspects of Emacs that make it especially useful and worthwhile
learning. Probably the most powerful is the ability to write macros
on-the-fly to do repetitive editing work for you.
The main idea is that you can ``capture'' a sequence of emacs commands
and have the system repeat this sequence over and over again for you.
Here's how it works.
- Tell the system you are starting to create macro.
- Type C-x (
- Now the system is recording the commands you type next. So type
in the sequence of commands you want the system to record to be reused later.
- Once you're done with the commands
- Type C-x )
- Now you've defined a keyboard macro. To tell the system to re-execute
the sequence of commands,
- Type C-x e
- You can tell the system to re-execute the command any number of times.
Say you want to re-execute it 10 times.
- Type ESC 10 C-x e
- You can save macros to be reused later by assigning them a name with
- M-x name-last-kbd-macro
Emacs Initialization File
You probably want to create a customized startup file for emacs. You save
this information in a file called .emacs in your home directory.
You can store macros in this file and tell the system what mode to start
up in by default. Here are some lines from my startup file along with
notes as to why they are there
- This gets rid of that annoying startup message:
(setq inhibit-startup-message t)
- This means set Auto Fill mode to be true. In Auto Fill mode,
inserting a space at a column beyond `current-fill-column'
automatically breaks the line at a previous space. So it does a nice
wrap-around for you without your having to hit return at the end of
the line.
(setq auto-fill-mode t)
- By default emacs stores a backup copy of every file you edit with
a ~ appended to the filename. I don't like this and so I turn it off.
(setq make-backup-files nil)
- These next few are more advanced.
- You can also assign commands to keyboard sequences. (Be careful --
--you might override a command that does something else.) For
example, I wanted a fast way to tell the system to go to a particular
line number in the file, so I define the following:
(global-set-key "\C-x\C-g" 'goto-line)
Now when I type C-x C-g the system asks me what line number to go to
and then goes there.
- You can tell emacs what mode to go into depending on the file
extension of the file you are editing. If I am editing a Java file
(whose name ends with .java) I want the system to use
java-mode, if I'm editing a latex file I want it to use latex mode.
To tell this to the system, I put the following in my .emacs file (the
formatting is messed up in html):
(setq auto-mode-alist
'(("\\.c$" . c-mode) ("\\.lisp$" . lisp-mode)
("\\.java$" . java-mode)
("\\.cl$" . lisp-mode) ("\\.html$" . c-mode)
("\\.tcl$" . tcl-mode) ("\\.tex$"
. latex-mode)))
Here is one printable reference card for emacs (in PDF).
Here is another online quick reference guide to emacs commands.
Here is a full version of the GNU Emacs Manual
