The Unix Platform

1
The Unix Platform

• originally developed by ATTs Bell Labs
• became popular in universities and small
  companies
• multi-user computing system
• runs on many different hardware platforms
• usually a CLI, though GUIs (Xwindows) are
  available
• most commands only 2 or 3 letters long

2
UNIX Flavors

• many different versions of UNIX
• UNIX as a trademark registered by ATT
• ULTRIX Digital Equipment Corporation
• AIX IBM
• XENIX developed for PCs
• AUX Apple Computer
• SunOS Sun Microsystems
• Mach NeXT computer

3
The Unix Platform

• division of work between a kernel and numerous
  shells
• kernel - the part of UNIX that does the real
  operating system work
• shells - the part of the UNIX that interprets the
  command that you type at the prompt
• Bourne shell prompt
• C-shell prompt

4
The Unix Model
your command
5
Interacting with Unix

• Unix is case sensitive
• Prompt tells you when the system is ready for
  input
• A shell interprets the command so that the kernel
  can process it.

6
Simple Unix Commands

• whoami
• shows login name, your terminal connection, and
  your last login
• date
• displays the current time and date

• pwd
• (print working directory) shows what directory
  you are in
• man command
• provides help on the command

7
Unix Pathnames

• Filename can be up to 256 characters long (in
  most versions)
• Pathnames have only 2 parts
• directory path
• file name
• all components separated by forward slash
• last component is always the filename

8
Unix Wildcards

• asterisk
• can represent zero or more characters
• can be placed anywhere in the filename
• alone is equivalent to DOS .
• question mark ?
• represent a single character

9
Listing Directory Contents

• ls
• ls -l
• long (detailed) listing
• ls -a
• all files listed, including hidden files, which
  begin with a dot (.)
• ls -F
• shows directories with a trailing /

10
Hidden Unix Files

• .login - environmental setting file
• .cshrc - initialization file
• .history - your transaction history log
• .mailrc - your mail program setting
• .newsrc - list of subscribed newsgroups

11
Changing Directories

• cd directory_name
• change to a child directory
• cd /
• change to the root directory
• cd ..
• change to the parent directory
• cd
• return to your home (login) directory

12
Creating Deleting Directories

• mkdir directory_name
• directory_name can be a full pathname, beginning
  with /
• directory_name can be a partial pathname
• rmdir directory_name
• remove a directory from the system
• the directory has to be empty to be removed

13
Copying, Moving, and Renaming Files

• Copying files
• cp file1 file2
• if file2 already exists it is overwritten
• if file2 does not exist, it is created

• Moving files
• mv file1 file2
• renames file1 to file2
• file2 may include a pathname
• mv file1 ../directory/file2
• the .. moves up one level

14
Displaying Text Files

• cat
• displays the entire contents of the file
• more
• display the content of a file one screenful at a
  time
• hit spacebar to go to the next page, return to go
  to next line
• type q to exit and return to the prompt

15
Deleting Files

• rm filename
• may use wildcards ( or ?)
• rm .com
• rm proj?.doc
• -e option displays a message after deleting each
  file
• be careful in doing rm

16
Unix File Protection

• Three categories
• user, group, others
• Three options
• read, write, execute

17
File Permissions

• Read permission
• allows looking at or making copies of the file
• Write permission
• allows making changes to the file
• Execute permission
• allows executing the file
• if a file is not executable, this permission is
  irrelevant

18
Directory Permissions

• Read permission
• allows listing of files in the directory
• Write permission
• allows renaming files and deleting files in the
  directory
• Execute permission
• allows using the directory in a pathname and
  changing to the directory

19
Setting Protections Syntax

• chmod who(or -, )what
• who specifies category (u, g, and/or o)
• use to add permissions, - to remove
  permissions, to set all possible permissions
• what specifies permissions (r, w, and/or x)

20
Setting Protections Examples

• chmod ux INDEX
• adds execute permission for the owner, all others
  left unchanged
• chmod go-w file1
• removes write permission for the group and others
• chmod ugorw testfile
• sets the permissions for everyone to read and
  write, but not execute

21
Unix Text Editors

• vi (VIsual editor)
• the first full-screen text editor on UNIX
• emacs
• customizable, extensible display editor
• pico
• simple, display-oriented text editor

22
Pico Editor

• designed for people to use when composing
  messages within pine
• pine composer
• can be used by itself

23
Starting Pico

• pico filename
• if file exists
• pico
• if file is being created
• name the file when you exit from pico editor

24
Pico Navigation

• use arrow keys to move the cursor
• use Backspace key to delete a character at the
  left side of the cursor
• use Enter key to go to the next line
• other functions are available with the
  combinations of Ctrl key () and a letter key

25
Pico File Recovery

• When a running pico process is disconnected, pico
  will save the current work if needed before
  exiting.
• Work is saved under the current filename with
  ".save" appended.
• If the current work is unnamed, it is saved under
  the filename "pico.save".

26
E-Mail Programs (UNIX)

• mailx
• generic mail system
• elm
• an interactive screen-oriented mail system for
  advanced users
• pine
• a screen-oriented message handling tool for
  novices

27
About Pine

• developed at the University of Washington in 1989
• written as an alternative to elm
• simple and clear
• contain only a minimum of basic features
• can also be used for reading newsgroups

28
E-Mailing with Pine (UNIX)

• type pine to start in menu mode
• type pine address to start in new message mode
• e.g., pine ell_at_it.rit.edu
• type pine -i to start in inbox
• shows the list of messages in the mailbox

29
Pine Mail Codes

• N new message
• D deleted message
• A replied message
• message sent directly to you
• X selected message

30
Signature Files

• Appended to the end of every message
• Comes from a .signature file in your home
  directory, which you can create with a text
  editor (e.g. PICO)

31
Pine Address Book

• Comparable to VAX aliases
• Can creat individuals or lists

32
USENET Newsgroups

• a worldwide distributed discussion system
• organized hierarchically with the broadest
  grouping first in the name
• some groups are moderated
• The name of each group is separated from its
  parent and its subgroups by a period.
• e.g., alt.collecting.pen-pencils

33
Newsgroup Hierarchies

• comp computer-related subjects
• news information about newsgroups
• rec recreational topics
• sci the various disciplines of science
• soc a wide range of social issues
• talk debate politics, religion, etc.
• alt alternative subjects
• misc subjects that dont fit elsewhere

34
Using Pine to Access Usenet

• At the Pine Main Menu, press L
• Select the second option, Select Here to See
  Expanded List, and then press Enter
• Press A for subscribing newsgroups
• Type a keyword and press X for finding
  newsgroups which contain the keyword
• Highlight the newsgroup you want to subscribe and
  press Enter twice

35
Using Pine to Read a Newsgroup

• After selecting a newsgroup to read, press Enter
  to open the newsgroup
• Select a message you want to read using the arrow
  keys
• To save a message in a folder in the pine
  program, press S for save
• To save a message as a file in your home
  directory, press E for export

36
Posting an Original Message

• After selecting a newsgroup to post a message,
  press C for composing
• Enter the subject heading and compose a message
• Press X then press Y for sending the
  message.
• It usually takes a couple of hours for a posting
  to reach the newsgroup.

37
Posting a Follow-up Message

• A follow-up message is a reply made to the group
  to comment on a posting.
• Those messages with Re preceding the subject
  heading are the follow-up messages
• After opening the message you want to reply to,
  press R for reply.
• When the prompt asks Post follow-up message to
  newsgroup?, type Y

38
Netiquette

• Keep in mind that you are communicating with
  people who may not share the common background
• Dont use all upper case letters. It usually
  means screaming.
• Use a smiley to inform the reader that you mean
  something in a humorous way.