What is Unix?

• A Computer Operating System

  • Software which provides a consistent means for programs to interact with the computer hardware

  • Provides for input, output, data storage and retrieval, program execution

  • Also, the collection of applications and utilities commonly installed on Unix systems

• Created in 1969/70 at Bell Labs as an outgrowth of the 1965 Multics project

  • 1963, Multics introduced the idea of multi-user, multi-tasking, multi-processor OS with hierarchical filesystem. Unix built on these ideas.

  • 1969, the first Unix is written at AT&T Bell Labs after AT&T drops out of the Multics project

  • Unix rewritten in C in 1973, introduced to the world in 1974 in an ACM article

  • AT&T prohibited from distributing Unix commercially by antitrust consent decree

  • Grew to 100,000 sites worldwide by 1984 – largely in academia where source code was available

  • Many “flavors” evolved – most based on either BSD (academia) or SysV (commercial & Govt.). Most differences are transparent to end users

  • Linux introduced in 1991 – circumvented copyright issues, leveraged the power of the Internet. Unix exploded in popularity with desktop computer users.

First Step – Logging in

• Usernames are eight or fewer characters in length, and, by convention, lower case

• Passwords are essential to system security – they should

  • ALWAYS:

    • Be eight characters long

    • Be a mix of letters in upper and lower case, numerals, and punctuation

  • NEVER:

    • Be in any dictionary

    • Be a proper noun

    • Use repeating sets of characters

The Shell - Primary User Interface to the Computer

• Two Main Alternatives

  • Sh – the bourne shell

    • The original shell – available on all Unix systems

    • Awkward in its original implementation, but newer varieties such as ksh and, especially, bash are a pleasure to use.

    • Provides a Complete Programming Environment: Variables, conditionals, loops, etc.

    • Most system shell scripts are written in bourne shell

    • Usually uses a “$” prompt

  • Csh – the “C” shell

    • Available on most systems

    • Written to provide a more familiar interactive environment for C programmers

    • Provides a Complete Programming Environment: Variables, conditionals, loops, etc.

    • Powerful variations are available – e.g. tcsh, zcsh, etc.

    • Usually uses a “%” prompt

Unix is more than the base OS – or kernel. It is a collection of hundreds of small programs, developed and refined over time to make the computer a productive tool. Orthogonality, combined with mechanisms for combining commands makes for a powerful environment.

Navigating the File System

• A hierarchical tree with a root – “/”, branches, and leaves

• Where am I? “pwd” – print working directory

• What’s here? “ls” – list the contents

  • “-l” the long listing

    • Permissions for Owner, Group, and Other

    • Read, Write, Execute

  • “-a” Show hidden files

    • “.” The current directory

    • “..” The parent directory

  • Globbing - *?[

    • "*" substitutes for zero or more characters

    • "?" substitutes for any single character

    • "[]" encloses a character 'class' (eg. [0-9] or [a-z])

  
  

• Moving About with “cd”

  • Absolute and Relative Paths

    • Absolute paths begin at the root - i.e with a "/"

    • Relative paths begin with the current directory

    • Use the double dots ".." to move upward in the tree with relative addressing

  • Using Shortcuts

    • The Twiddle

      • '~/' is a shortcut to your home dir

      • '~/someuser' is a shortcut to someuser's home dir

    • The Dots

      • 'cd ..' moves up one level in the directory tree

      • 'cd ../..' moves up two levels

• Creating and Removing Files and Directories

  • mkdir

  • Redirection – a hint at the power of Unix

    • 'echo sometext > somefile'

    • 'date > datefile'

    • 'date >> datefile'

  • rm, and rmdir – Be Careful!!

• Looking at What You’ve Got

  • cat and more

  • head and tail

Getting Help from the MANual

• How to Ask When You Don’t Know the Question

  • apropos & man –k

  • whatis

• The Sections

  • 1 – User Commands

  • 2 – Programmer’s Manual – system calls

  • 3 – Programmer’s Manual – functions

  • 4 – Special Files

  • 5 – Config Files

  • 8 – Sysadmin Commands

Editing Text Files with Emacs and Vi

• VI – you can’t escape it

  • Available on every Unix system

  • Modal – You’re either entering commands or editing

  • Similar commands are used in many other system tools descended from common ancestry – sed, ed, etc.

  • A Command Overview

    • Inserting Text

      • “i” is for INSERT, “a” is for APPEND

      • “o” is for OPEN a line below, “O” is for OPEN above

    • Deleting Text

      • “x” is for EXPUNGE

      • “dd” is for DELTE LINE

    • Cursor Movement

      • “h” moves LEFT

      • “l” moves RIGHT

      • “k” moves UP

      • “j” moves DOWN

      • “$” moves to the end of the line

      • “0” (zero) moves to the beginning of the line

      • “G” moves to the end of the file

      • “:0” moves to the beginning

    • Saving and Quitting

      • “:w” WRITES a file

      • “:q” QUITS

      • “:wq” WRITES & QUITS

      • “:q!” QUITS, not questions asked!

• Emacs – all things to all people

  • Available on most systems

  • Infinitely extendable – read mail, diagnose your psychoses, etc.

  • Developed by the GNU folks by programmers, for programmers

  • Similar commands are used in other editors – notably Pico, the 'Pine' editor

  • Supports X Windows

  • Uses Control (the <Ctrl> key) and Meta-key (usually <Escape>) to distinguish commands from input

  • A Command Overview

    • Cursor Movement

      • C-f move FORWARD one character

      • C-b move BACKWARD one character

      • C-P move to the PREVIOUS line

      • C-n move to the NEXT line

      • C-a move to the BENNING of the line

      • C-e move to the END of the line

      • C-x[ move to the beginning of the FILE

      • C-x] move to the end of the FILE

    • Deleting Text

      • C-d DELETES a Character

      • M-d DELETES a Word

      • C-k KILLS a Line

    • Retrieving Text

      • C-y YANKS the Kill Buffer

    • Formatting Text

      • M-q REFORMATS a paragraph

    • Saving and Quitting

      • C-x C-s SAVES a file

      • C-x C-c QUITS

    • Seeing the Doctor

      • M-x “doctor” <return>