Getting familiar with the UNIX environment here at PSU.

1
An Introduction to UNIX

• Getting familiar with the UNIX environment here
  at PSU.
• Presented by Mr. Waddell

2
Follow Along

• You can follow along with the demo by downloading
  these slides from the ACM club website.
• http//www.acm.pdx.edu/presentations

3
Topics

• Remote login
• Setting up your environment
• Basic commands
• The directory tree
• A few odds and ends

4
Remote Login
You can login to any of the CS UNIX and CS Linux
machines from the Internet.

• Hack your code and run/debug your programs
• Copy files to and fro

5
Remote Login

• Windows
• PuTTY is a Secure Shell (SSH) client.
• Google for PuTTY
• Snag PuTTY, as well as PSCP and PFTP.Linux
  Users
• Hopefully you already know about ssh...

6
Remote Login

• With your CS UNIX/Linux account username and
  password.
• Hosts cs.pdx.edu (Sun Solaris, on
  SPARC) linuxlab.cs.pdx.edu (Linux, on
  x86) odin.pdx.edu (Sun Solaris, not maintained
  by the CECS department)
• Pick your celestial body. i.e. atlas.cs.pdx.edu
  (Sun Solaris) tao.cs.pdx.edu (Linux)

7
Remote Login

• PSFTP (or sftp on a UNIX machine) allows you to
  copy files back and forth from using an ftp-ish
  user interface.
• PSCP (or scp on a UNIX machine) also allows you
  to copy files back and forth, but without the
  interface.

Note The UNIX (sftp, scp) utilities do not have
a graphical interfaces.
8
Some Basics

• Your shell, and how to change it
• Changing your password
• Core utilities you should be familiar with

9
The Shell

• Put down your mouse
• Shell prompt terminal your friend
• Enter commands and witness the results
• Anything that you wish to do on a UNIX machine
  can be done with your shell prompt (mostly)
• First Step Change your shell from csh!

10
Changing Your Shell

• csh is oldschool
• Not exactly as feature rich, as friendly, nor
  convenient as other shell programs
• A better alternative is tcsh
• Command history
• Tab completion (of sorts)
• More compatible with the configuration of the CS
  machines

11
Changing Your Shell

• The program to run (from a prompt) chsh
• It will prompt you for your password
• Enter the shell you want to use instead.
  i.e. /bin/tcsh
• Logout, and then back in. Note It may take a
  minute or two to propagate.

12
Changing Your Password

• The program to run (from a prompt) passwd
• It will ask you for your current password, then
  twice for your new password.
• A good password consists letters numbers and
  perhaps other symbols (, -, , ...).

13
Core Utilities

• The basic utilities you probably should know
  about.
• ls (List contents of directories)
• pwd (Displays your current location)
• cd (Move around from place to place)
• rm (Remove a file or directory)
• mkdir (Make a directory)
• cp (Copy files and directories)
• mv (Move, or rename files and directories)

14
Core Utilities

• More basic utilities
• addpkg (Install software i.e. Java)
• lpr (Print a document)
• lprm (Remove your print job)
• man (Displays documentation)

15
Man Pages

• Most programs you will be using have a man page.
• The format command OPTIONS arg1 arg2 ...
• Do not include the actual square brackets
• arg1 and arg2 are not optional
• Forms of options (aka flags, aka arguments) -a
  where a is a single character (OR) --blah
  where blah is a single word

16
Man Pages

• You can also invoke the program to tell you more.
  (i.e. displaying a usage description) command
  --help (OR) command -h

17
The UNIX File System

• The file system (obviously not exhaustive)Note
  the top, naturally, is called root

/
usr
u
...
bin
...
your_username
...
18
The UNIX File System

• Try this
• cd /
• ls

You are here
/
...
usr
u
19
Relative Paths

• To get back home
• cd u
• cd your_username
• ls

/
u
You are here
your_username
20
Relative Paths

• Both times when cd was used cd u cd
  your_usernameyour target (u, and your_username)
  were contained in the directory you currently
  were in.
• u is relative to root (/)
• your_username is relative to u

21
The UNIX File System

• Try this
• cd /usr
• ls

/
usr
You are here
bin
...
22
Absolute Paths

• To get back home
• cd /u/your_username
• ls

/
u
You are here
your_username
23
Absolute Paths

• This time neither u nor your_username were
  relative to where you currently were.
• You have to tell cd exactly where to look cd
  /u/your_usernameThis tells cd that u is
  contained at the root.
• Generally any path that begins with a / is an
  absolute path

24
More Than One Way Home

• Getting Home--here is a list of helpful
  equivalences cd cd cd / cd
  your_username cd your_username/

25
The UNIX File System

• Dot and Dot-Dot.
• . and .. are very important to you.
• . denotes your current directory
• .. denotes the parent directory (one level up in
  the tree)
• Examples cd . cd .. ./a.out

26
File Permissions

• Allowing everyone to see your code is probably
  not a bright idea.
• You may allow access to certain files or
  directories.
• Though, not covered here, it is possible to allow
  specific people access to your files.
• chmod

27
File Permissions

• The basic modes
• Read
• Write
• Execute
• The modes apply to
• User (you)
• Group (i.e. them)
• Global

28
File Permissions

• Viewing permissions ls -l file.txt
• The format-rw-r--r-- 1 wad them 0 2006-01-27
  1705 file.txt
• The first segment rw- (read, and write) are in
  the user segment. i.e. me.
• The second segment r-- (read only) is in the
  group segment. i.e. group them have read
  permission.
• The last segment r-- (read only again) is in
  the global segment. i.e. anyone can read this
  file.

29
File Permissions

• Changing permissions chmod gw file.txt ls
  -l file.txt-rw-rw-r-- 1 wad them 0 2006-01-27
  1705 file.txt
• Now everyone in the group them can write to
  this file... Not a good idea!
• To protect the file from everyone but yourself
  chmod og-rw file.txt -rw------- 1 wad them 0
  2006-01-27 1705 file.txt

30
File Permissions

• You can also set permission on directories. ls
  -al foodrwx--x--x 48 wad them 2048 Jan 27
  1628 foo
• Note the d as in directory.
• The quick and dirty about directories
• If the directory is executable, one can cd into
  it.
• If the directory is readable, one can use ls to
  view the files contained within.

31
Some Other FAQish things

• To check your disk quota (135 MB) quota -v
• Copy files from ODIN scp file.on.odin.txt
  username_at_cs.pdx.edu/
• Print from ODIN cat file.to.be.printed.txt
  username_at_cs.pdx.edu -C 'lpr -Pfab13501bw1'

32
Play With It

• The only way to become a UNIX guru is to play
  around.
• Try Linux (Ubuntu, Debian, Slackware, etc.)
• Read the man pages.
• Tutorials
• http//www.cat.pdx.edu/tutors
• http//acm.pdx.edu
• If all else fails -gt Google