Navigating Unix
UCR Technical Seminar Series
Fall ’03
Dan Berger dberger@cs
Outline
Unix History/Philosophy
File System Basics
Utilities You Shouldn’t Leave ~/ Without
Web, Mail, Office, Windows
Printing
Looking for Help
Asking for Help
Learning More
Slides online at http://www.cs.ucr.edu/~dberger
A Brief History of Time^wUnix
Born in the late 60’s at AT&T/Bell Labs out of the
MULTICS project. Ran on a PDP-11.
Thompson, Ritchie, Kernighan, among others.
In the 70’s AT&T was prohibited from selling
Unix, so they gave it to universities.
The contributions from some of those
universities (such as Berkeley), and later from
MIT, evolved Unix into the basic form it still holds
today.
Unix Philosophy
Small tools, each of which does one job well.
Build pipelines of these tools to accomplish loftier goals.
Users interact with the system through the “shell” – a
command-line interface.
It’s all about user choice – why have one when you can
have three?
“Here’s the rope, there’s the tree – help yourself.”
File System Basics: /
There’s no “C:\”, or “Macintosh HD” – the file
system is a tree, rooted at “/”
Additional volumes can be “mounted” at (fairly)
arbitrary spots in the tree.
Some key portions of the tree:
/bin
/etc
/dev
/home
/lib
/proc
/usr
/mnt
/tmp
/var
. and ..
Every directory has two special entries: “.” and
“..”
“.” is the current directory
“..” is one level up toward the root (/)
Confusing them can be unpleasant…
Trick Question: what directory does “/..” refer to?
Home Directories
Unix is inherently multi-user – and in a multi-user
system, users can’t scribble their files around at
random.
Each user on a Unix system has a “home
directory” – it’s contents, organization (or lack
thereof) are completely up to you.
When you log in, you are placed in your home
directory (abbreviated ~/).
Manipulating Files from the Shell
Task
Change Directory
Copy
Display disk Usage
List Files
Move
Make Directory
Print Working Directory
Remove
Remove Directory
Command
cd target
cp src dst
du target
ls (ls –a, ls –l)
mv src dst
mkdir target
pwd
rm target
rmdir target
File Permissions
Recall: unix is multi-user – the file system keeps
track of who’s allowed to read, write, and
execute a given file.
The world is divided into three: the user that
owns the file, other users in the group that owns
the file, and everyone else (other).
Changing the mode of the file is done with the
chmod command.
Permissions are octal bit vectors – one byte for each
of the three groups and a prefacing special byte.
Permissions (Cont.)
Directories have permissions too:
read: read the contents of the directory (not
necessarily the contents of the files themselves)
write: remove and rename (but not create) files in the
directory (not necessarily write to existing files)
execute: access the directory (cd into it)
Newly created files (and directories) have their
default permissions set to (7777 && umask).
umask will report your umask.
Utilities Not to Leave ~/ Without
ssh – secure shell – execute commands (or get
an interactive shell) on a remote machine over
an encrypted network connection.
It’s so cool and versatile, it’s getting it’s own seminar!
scp – secure copy – copy files between two
hosts over an encrypted network connection.
(mostly replaces FTP)
rsync – keep directory trees on different
machines synchronized.
Browsing the Web
Mozilla – it’s cross platform and standard and
buzz-word compliant.
Galeon – part of the GNOME desktop – it’s built
on (and embeds) mozilla.
Reading Mail
Remember “it’s all about choice?” There are
many possible mail readers – the department
recommends (i.e. the systems group supports):
Evolution – something of a MS Outlook “work-alike,”
but without the propensity for worms and other
unpleasantness.
Other clients include mozilla (gui), mutt (curses).
imaps://imap.cs.ucr.edu
smtp://mail.cs.ucr.edu
Handling Windows Documents
Office documents (Word, Excel, Powerpoint) can
be opened using Open Office (ooffice).
Try gnumeric on your Excel documents, and
abiword on your Word documents.
Printing from Unix
PostScript is the lingua franca of Unix printing.
That means if what you want to print isn’t
PostScript, something has to do the conversion.
It also means that if your printer doesn’t understand
PostScript, something has to do that conversion as
well.
Fortunately, all the department printers
understand PostScript
enscript
If you have an ASCII file (e.g. source code) that
you want printed – enscript is your friend.
It will turn ASCII into PostScript – and even print
two pages to a page.
Add the following to your .bashrc:
export ENSCRIPT=“—landscape –columns=2 –
borders –line-numbers –pass-through”
enscript –P printername source.cc
Printing PostScript Files
If you already have a PostScript file, your life is easier:
lp –P printername file [file…]
Note that PDF’s are not PostScript – don’t send them to
lp unless you want to waste a ream of paper.
Also note that printing a postscript file through enscript
(or a2ps) will likely result in similar waste.
Checking Your Print Job
lpq –P printername - shows the print queue for
the given printer.
If your job doesn’t appear on the printer – check lpq
before you submit it again – make sure it’s not just
stuck behind another job.
lprm –P printername – removes your job from
the specified queue.
Running Windows
If you absolutely must run windows – just type
“windows.”
It launches a Windows Terminal Server client.
You won’t remember this when you need to – but
press Control-Alt-Enter to toggle full screen
mode.
Finding Help (man, info, google)
man man
man subject
man –k subject
info subject
info –apropos=subject
http://www.google.com
google://your+question+here
Asking for Help
If you’ve looked in all the places mentioned in
the previous slide, and you still can’t figure it out
– there are some simple rules that will improve
your chances of getting a good answer from a
human:
http://www.catb.org/~esr/faqs/smart-questions.html
Who To Ask?
Lab mates, friends, strangers, and finally:
systems@cs.ucr.edu
Learning More
Teach Yourself Unix in 24 Hours by Dave Taylor
Unix Fundamentals course (undergrad, upper
division).
If you’re interested, drop me an email and I’ll try to
get the course offered once we have sufficient
interest.
Install Linux on your home machine (or
notebook)
Linux Administration: A Beginners Guide by Steve
Shah (a UCR alum).
Shell “Scriptlett’s”
shell is also a powerful system scripting
language – supporting conditionals, loops,
variables, etc.
for file in *; do
echo $file;
done
x=0
while [ $x –lt 10 ]; do
let x=x+1
echo $x
done
if [ -f somefile ]; then
echo “it exists”;
else
echo “doesn’t exist”;
fi