Goals: Finding your sea legs
In this session you will:
- learn what unix is and isn't
- learn how unix is used today
- learn how unix is different
- get a feel for where you are, what is around you, and what you can do
What is unix, anyway?
- origin: Dennis Ritchie and Thompson at Bell labs, concentrated on programming (C) and group projects. Unix and C develop side by side. Ritchie now involved with Plan 9 and Inferno.
- Unix Wars: System V by ATT, BSD by Berkeley (based on ATT code).
- commercial splintering: SysV (AIX, HPUX, etc.), BSD (Solaris, DEC Ultrix) p.18
- linux (Red Hat, Slackware, Debian, SuSE distributions), BSD (freeBSD, netBSD)
- Mac OS X
- Pragmatic definition: unix = "unix-like", not the trademarked name owned by AT&T (then USL), then Novell, then X/Open). If it quacks like a duck...
- Bottom line: Various flavors of unix (unixes, unices, unixen) and versions of flavors will be similar with differences. Keep the Big Picture in mind!
How is unix commonly used?
- Stability: micro and minicomputers for research and busies
- Portability: recompile apps and go! Unix is platform-agnostic
- Price: massively parallel computing
- Pared down functionality: Internet and ISP servers
- Availability: it's everywhere
- hobbyist fun
How is unix different
Unix has a distinctive philosophy and a specific community temperament.
- Built as an OS with a specific group in mind; wonky and arbitrary ("cat")
- attracts hackers (not crackers), academics, and do-it-yourselfers as well as those that demand system stability.
- There is a huge community of *nix folks out there to compare notes with, but getting heard and answered (and not getting shredded) takes some preparation. To be accepted in the ranks and get help:
- Try to figure it out yourself.
- RTFM: faqs, how-tos, manuals, READMEs, etc
Trick of the Trade |
A quick way to get up to speed on anything at all is to do a web search on [topic] FAQ. The FAQ for any given topic will give you the thumbnail sketch you need to get started, or to be popular at the next cocktail party. |
- Do the homework (newsgroups, mailing lists)
Trick of the Trade |
If you're getting a reproducible error message, you can cut/paste it into a newsgroup search like Google-Deja. This will pull up messages from people who are having (and solving) the exact kind of problem you are having. |
- If you're still stuck, ask your question in such a way that the gurus know you've tried all the other steps. Be rational: no begging, no demands, no excessive punctuation. Project "cluefulness", not "cluelessness". Ask for pointers to appropriate reading material rather than an outright answer.
Dive in!
- multi-user OS requires a login. Admin cannot see pw, and your login should not change.
- X desktop - use a terminal instead. (further reading on X: chapter 5)
- The command line
- the login: what do we see? Top to bottom, left to right.
- case sensitivity!
whoami - what is my login?
groups - what workgroups am I in (really or potentially)
pwd (present working directory) - where on the filesystem am I?
You login to your home directory ~[username]
You own the files and dirs in your home dir. (permissions will come later)
hierarchical filesystem branching off of root ("/")
ls -l - what is here with me?
Trick of the Trade |
Experienced users do two things habitually: - Reality checks with
ls/pwd, and - save their work.
|
A digression about the Tao of Unix
- an application should "do one thing well"; allow for chaining IO, terse commands.
- What's a switch or option?
- changes the app's behavior
- looks like this:
-v or -x somefile.txt
- may be able to combine switches...
- What's an argument or parameter?
- Why does it matter: discrete rather than monolithic applications
- How do I remember all of this? You don't:
- help switches
-help --help or no args at all
man (manual) pages: man [something]
apropos [keyword] to find manpages
whatis [appname] for one-liner help
- references
The command line, continued
- The command line
- show a directory listing and look for these in the display: . and .. What do they mean?
Treading water
- changing your
passwd
- make a file to manipulate:
echo "this goes in a file" > outfile
- look for it in the directory (hint: ls)
- make a new directory:
mkdir
- change directories to it:
cd. Special uses of CD: cd, cd ~, cd ~user
- move your file into the new directory:
mv - verify it really happened
Trick of the Trade |
Perform a "sanity check" after you do something: did it work? How do I know it worked? Did any output land where it was supposed to land? |
- .hide the file with a .dot. (new term: .dotfiles - config files frequently end in "rc")
- copy the hidden file to a new name:
cp
- remove (delete) the .hidden file:
rm. There is no undelete...
Sometimes rm or other destructive commands are aliased to rm -i. You can force a non-aliased form thusly: 'rm'.
rmdir removes empty dirs
using absolute and relative paths p.70
- make a sister directory
- move to it in one step
Have a peek around
- move out of your directory and see what else is on the system
- look at your PATH to see where the apps are; go there and look around
Shell games
- you're already using a shell:
ps
- There are various shells available
sh - Bourne shell - always present. Somewhat limited.
csh - C shell - has a C-like syntax for scripting
bash - Bourne Again Shell - augmented bourne
ksh - Korn - like bash + csh.
- other, highly specialized shells designed for small footprint, security, etc.
- benefits of advanced shells: history, richer feature set
- changing shells
Rescue operations
- Stuck? Try breaking out with [ctrl-c].
- terminal gone insane? Try a couple of iterations of
stty sane and reset
logout!
Homework
- read news:comp.unix.questions
- Shells, p. 24-27
- Permissions, 389-393
http://www.mousetrap.net
$Id: day1.orb,v 1.15 2002/09/03 19:48:42 mouse Exp $
Remember, your login is based on your machine's hostname, not on any other number.
~/[initials] refers to the subdirectory under your homedir, named after your initials. Everything except for .dotfiles will be stored in your ~/[initials] directory.
