ICSA 202: Computing Tools

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ICSA 202 Computing Tools Environments

• Week 5 Introduction to UNIX

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The Unix Platform

• Multi-user computing system
• Runs on many different hardware platforms
• Originally developed by ATTs Bell Labs
• usually a CLI, though GUIs (Xwindows) are
  available

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UNIX Flavors

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

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The Unix Platform

• UNIX divides 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

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The Unix Model
your command
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Interacting with Unix

• Unix is case sensitive
• Commands are very short, often not intuitive
• System does not provide feedback for successful
  commands
• The shell interprets the command so that the
  kernel can process it.

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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 specified

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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

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Unix Wildcards

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

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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 /

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Hidden Unix Files

• Files that begin with a . are hidden
• .login - environmental setting file
• .cshrc - initialization file
• .history - your transaction history log
• .mailrc - your mail program setting

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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

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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

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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

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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

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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

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Unix File Protection

• Three categories of ownership
• user, group, others
• Three options for protection
• read, write, execute

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File Permissions

• Read permission
• allows viewing or copying of the file
• Write permission
• allows modifications to and deletion of the file
  and deletion
• Execute permission
• allows execution of the file
• if a file is not executable, this permission is
  irrelevant

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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 use of the directory in a pathname and
  changing to the directory

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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)

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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

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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

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Pico Editor

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

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Starting Pico

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

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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

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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".

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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

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About Pine

• developed at the University of Washington in 1989
• menu-driven
• contains only a minimum of basic features
• can also be used for reading newsgroups (covered
  next week)

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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

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Pine Mail Codes

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

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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)

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Pine Address Book

• Comparable to VAX aliases
• Can create individual aliases or lists