This document provides an introduction and overview of the Unix operating system. It covers topics such as getting help, the file system, the shell, network security, email clients, text editors, input/output redirection, printing, process management, and the X window system. The document is intended to help new Unix users understand basic Unix concepts and commands.

1. Welcome to Unix
Crafted by the CSUA at Berkeley
http://csua.berkeley.edu
Presented 8/29/2002

2. Redistribution
• The authors (nor anyone else) provides no
warranty or claim of accuracy of this
document. Use at your own risk.
• You may use this document in whole or part
according to the terms of the GPL. See
http://www.gnu.org/copyleft/gpl.html for
details.

3. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

4. What is it and where do you get it?
• An operating system used on everything
from servers to embedded systems.
• To you, probably a prompt:
~> type stuff here
• You get a temporary account when you take
a CS class. Get a (more) permanent
account from the OCF or CSUA. Or buy a

5. If you know only one thing,
know how to RTFM.
~>man command
• gives you help on that command.
~>apropos keyword
• tells you all man pages that contain keyword.

6. How to get help.
• Come to the CSUA office, 343 Soda.
• HKN is next door the CSUA.
• Go to the OCF in the MLK Heller Lounge
when someone is holding staff hours.
• Post your question to a newsgroup (like
your class newsgroup).
• Hit the man pages/web first !

7. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

8. Files and Directories:
Naming something gives you power over it.

9. Absolute Addressing

10. Addressing relative to your home dir.

11. Addressing relative to your current dir.

12. File system commands
• pwd - report your current directory
• cd <to where> - change your current directory
• ls <directory> -list contents of directory
• cp <old file> <new file> - copy
• mv <old file> <new file> - move (or rename)
• rm <file> -delete a file
• mkdir <new directory name> -make a directory
• rmdir <directory> -remove an empty directory

13. getting recursive
• remove a directory and its contents:
rm -r <directory>
• copy a directory and its contents:
cp -r <directory>

14. File permissions.
• There are 3 kinds of people in the world: you (user),
your friends (group) and everyone else (other).
• Each sort of person may or may not be able to read,
write, or execute a file.
>ls -l .forward
-rw-r--r-- 1 darin csua 23 Jan 23 2002 .forward
>ls -l .cshrc.local
-rwxr-xr-- 1 darin csua 2988 May 19 00:48
.cshrc.local*

15. executing
• “executing” a file means running it as a
program.
• “executing” a directory means setting your
current directory to it using cd.

16. Changing File Permissions
• make a file readable to your friends:
chmod g+r <filename>
• change who owns a file:
chown <user> <filename>
• change to which group the file belongs:
chgrp <group> <filename>

17. touch
• look at the full listing again:
>ls -l .forward
-rw-r--r-- 1 darin csua 23 Jan 23 2002
.forward
• Each file has a date stamp of when it was modified.
• Use touch to set the timestamp to the current clock.
touch <filename>
• Touch creates the file if it didn’t exist beforehand.

18. Symbolic Links
• use ln -s <old file> <second name> to create a
symbolic link to a file.
>ls -l .forward*
-rw-r--r-- 1 darin csua .forward
lrwxr-xr-x 1 darin csua .forward.link@
-> .forward
• The first “l” tells you that it’s a symbolic link.
• Symbolic links can be used as if it were its target.

19. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

20. what’s a shell?
• The shell is the program that
runs when you log in. It prints
the prompt and reads what you
type, invokes programs, etc.
• your window to the Unix world.
• use “chsh <new shell>” to change your shell

21. File Globbing
• some commands can work on many files at once:
~> rm file1 file2 file27
• Use * to match any number of unknown characters
~> rm file*
• Use ? to match one unknown character.
~> rm file?

22. (un)aliasing
• create shortcuts for yourself
~>alias ll “ls -la”
• Use alias with no arguments to discover
current aliases
~>alias
rm rm -i
ll ls -la
• Type “unalias rm” to remove alias.

23. shell variables, echo
(tcsh) ~>setenv BOB “joe”
(tcsh) ~>printenv BOB
joe
(tcsh) ~>echo $BOB
joe

24. PATH: a very important shell variable
>echo $PATH
/
home/d/da/darin/bin:/opt/local/bin:/opt/local/bin/pbmuti
ls:/usr/bin:/usr/sbin:/opt/SUNWspro/bin:/usr/ccs/bin:/op
t/local/X11/bin:/usr/dt/bin:/usr/openwin/bin:/opt/local/
gnu/bin:/opt/local/games/bin:/usr/ucb:./
• If a program (like ls) is in one directory found in
your path, then typing it (~>ls <enter>) will execute
it.
• Otherwise you can type the full absolute address to

25. finding things in your PATH.
• Type “which <command>” to find the location
of the program which would be run when you
type <command>.
• If you don’t remember if it was chgrp or
chgroup, type “ch<control-d>” to get a list of
commands that starts with ch.
• when all else fails, use “find” to find a file.

26. Other useful pre-defined shell variables
• HOST what computer you’re logged into
• PAGER program used display man pages
• PWD current directory
• GROUP what group you’re in
• USER your login

27. Shell scripts.
• If you have a bunch of commands you’d like to
automate, you can put them on separate lines of a
file. Then type “source <file>” to run the script.
• If the first line of your script looks like
#!<program name>
then you can make the script executable. When it
executes, it uses <program name> to interpret the
contents of the script.

28. Login scripts
• Most people have a script that executes
when they log in. It is commonly used to
set up one’s PATH and aliases.
• Ask someone to help you start your own
login script.

29. screen is your friend
• You can use the program “screen” to run several
shells from one window.
• create a new shell by pressing <ctrl-a> c
• switch shells by pressing <ctrl-a> <number>
• use “<ctrl-a> d” to detach a session and come back

30. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

31. Your Options
• Abstinence
(switch majors, unplug your computer)
• monogamy
(use only one computer, do not use network)
• protection
(also known as encryption)

32. What not to use.
• telnet, ftp, rlogin
• all your data (including your password) is
transmitted plain text over the network.
• from library machines you can use the java
ssh client from a web browser.

33. using ssh keys
• use “ssh-keygen” to generate a
public/private set of keys. You keep the
private key and append the public key to
authorized_keys.
• You can now log in using either your
password or the private key file.

34. using secure copy: scp
• copy local to remote
scp <source file> user@machine:<path>
• copy remote to local
scp user@machine:<path> <source file>

35. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

36. the program mail
• “mail”: useful for sending:
>mail darin@csua
Subject: hello
Cc:
hi there
this is a message
.

37. other console based options
• elm - quick and simple, easy to use, but
doesn’t handle attachments very well.
• pine - more complete. the “standard”
• mutt - most modern/complex.

38. accessing mail remotely
• netscape, outlook, eudora, and others can
get at your mail using POP or IMAP.
• POP takes the messages off the server to
your local computer.
• IMAP only reads headers, but leaves mail
how it is on the server. Works well if you
wish to use console based email.
• ALWAYS use SSL (encryption).

39. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

40. vi
• is an editor available on all decent Unix
systems. Developed at Berkeley.
• Has two modes: command and insert. In
insert mode you can type normally.
• Press escape to get into command mode. In
command mode each letter is a command.
hjkl ⇔ ←↓↑→

41. pico - the pine composer
• the simplest visual editor available on most
Unix systems.
• all possible commands displayed at bottom
of screen. (control-somethings)
• no real surprises

42. emacs
• Always has one major mode running,
potentially several minor modes.
• stands for editing macros - designed by and
for lisp programmers.

43. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

44. STD*
• All terminal programs have:
– standard output, which is usually your screen
– standard input, which is usually your keyboard
– standard error, which is also the screen

45. redirect output to a file with >
• If you type who at the prompt, you will get
a list of who is logged into the system.
• If you type who >f, a file named f will be
created and the standard output of who will
be placed in that file instead of to your
screen.

46. > vers >>
• By default, who >f will overwrite the file f.
• Use who >>f to append to f rather than
overwriting it.

47. redirecting input from a file with <
• The program sort will sort its standard
input and then print it on standard out.
• To sort the lines of file1 and display:
sort < file1
• To sort the lines of file1 and save in file2:
sort < file1 > file2

48. The output of one program can
be the input to another.
who | sort
• The output of who is sorted and shown on
your terminal screen.

49. grep
• grep shows only those lines containing its
search pattern.
• To see all lines in a file containing ‘bob’:
grep ‘bob’ < file1

50. The cat command
• the arguments to cat are concatenated together
and displayed on stdout. To view a file:
cat file1
• if no arguments, cat puts on stdout whatever
you type on stdin, so this does the same thing:
cat < file1

51. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

52. printers have stupid names
• The printers downstairs are named “lw274”.
• The printer in 330 is called “lw330”.

53. how to print a .ps file
• syntax:
lp -D<printer> <filename>
• example:
lp -Dlw330 myfile.ps

54. how to print a .pdf file
• convert it to .ps first!!!
• use the pdf2ps utility program.
pdf2ps input.pdf output.ps

55. how to print other file types
• Convert them to .ps first!!!
• The program a2ps (anything to .ps) works
most of the time.

56. How to check the printer’s queue.
• syntax:
lpq -P<printer_name>
• example:
lpq -Plw330

57. How to cancel your print job.
Type “cancel”.

58. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

59. To start a process in the
background, use “&”.
• example:
big_program > output &
• big_program will not have input!

60. managing jobs
• To suspend the currently active program,
use <control-z>.
• To return to the program you just
suspended, type “fg”
• To put the program you just suspended in
the background, type “bg”

61. To see a list of your programs
running, type “ps”.
>ps
PID TTY TIME CMD
866 pts/1 00:00:00 tcsh
872 pts/1 00:00:00 ps

62. use kill to end a process
>ps
PID TTY TIME CMD
866 pts/1 00:00:00 tcsh
874 pts/1 00:00:00 cat
875 pts/1 00:00:00 ps
>kill 874
[1] Terminated cat

63. kill -9
• If kill <PID> doesn’t end your
process, use kill -9 <PID>

64. Outline
I. getting help
II. the file system
III. the shell
IV. safe computer sex
V. email options
VI. and lesser editors
VII. input and output redirection
VIII.printing
IX. process management
X. X

65. cutting and pasting
• Highlight some text in any window.
• Hit the middle mouse button in another
window.
• The highlighted text appears.
• There is no “saving to the clipboard” step as
in Microsoft’s Windows or MacOS.

66. Changing your fonts.
• <control-leftclick> in xterm
• edit -->preferences --> fonts
in netscape.

67. Changing your window manager.
• Your ~/.xsession gets run when you
log into X windows, the last line sets which
window manager you are going to use.
• You probably want someone to set up your
X configuration for you the first time.

68. Using X windows at home on a
MS-Windows machine.
• You need to get a program called a program
called an “Xserver”. Exceed works well
and is free for academic use.
• You must allow X-forwarding through your
ssh client. Putty is good for this.