Unix Lecture Notes

Introduction to System Programming
	Introduction
	A Programming Illusion
	Cornerstones of UNIX
		Files and the File Hierarchy
		Processes
		Users and Groups
		Privileged and Non-Privileged Instructions
		Environments
		Shells
		Online Documentation: The Man Pages
	The UNIX Kernel API
		System Resources
		System Calls
		System Libraries
	UNIX and Related Standards
		The Problem
		The Solution: Standards
	The C Library and C Standards
	Learning System Programming by Example
	The UNIX File Hierarchy
		About Pathnames and Directories
			Working with Directories
		Files and Filenames
			Filenames
			What is a File?
			Working with Files
			File Attributes
			Viewing and Modifying File Attributes
			Symbolic Links
	Under the Hood: How Logging In Works
	UNIX From The System Programmer's Perspective
	A First System Program
		A First Attempt at the more Program
		A Bit About Terminals
		Device Special Files
			Examples
		A Second Attempt at the more Program
		What Is Still Wrong?
		A Third Attempt at the more Program
	Where We Go from Here
Brief History of UNIX
UNIX at the User Level
	Notation
	Logging In
	Logging Out
	Online Help: The man Pages
	Shells
		Shell Features
			Standard I/O and Redirection
			Command Separators and Multitasking
			The Shell as a Command
			Scripts
			Some Historical Remarks About Shells
Login Records, File I/O, and Performance
	Introduction
	Commands Are (Usually) Programs
	The who Command
	Researching Commands In UNIX
		Reading Man Pages
		Man Page Searching
	Digging Deeper into the who Command
		Reading the Correct Header Files
		What Next?
	Writing who
		Reading Structures From a File
		The open() and close() System Calls
		A First Attempt at Writing who
		What to Do with System Call Errors
		Displaying login Records
		A Second Attempt at Writing who
			Suppressing Records That Are Not Active Logins
			Displaying Login Time in Human-Readable Form
		A Third Version of who
		A POSIX-compliant Version
		Summary
	Using a File in Read/Write Mode
		Opening a File in Read/Write Mode
		Logout Records
		Using lseek to Move the File Pointer
		Updating the utmp File on Logout
		Another Use of lseek
	Performance and Efficiency : Writing the cp Command
		What cp Does
		Opening/Creating Files For Writing
			Creating/Truncating Files
			Writing to Files
		A First Attempt at cp
		Timing Programs
		Buffering and its Impact on Performance
		System Call Overhead
		System Buffering
		Memory Mapped I/O
	Returning to who
		User-Defined Buffering
		Final Comments
	Filters: An Introduction
		sort
		head and tail
		cut
		Regular Expressions and grep
			Examples
		The Rest of the grep Family
			egrep
			fgrep
	File Globs
3 File Systems and the File Hierarchy
	3.1 Introduction
	3.2 File System Abstraction
	3.3 File System Mounting
	3.4 Disk Partitions
	3.5 UNIX File Systems
	3.6 The Principal Components of a UNIX File System
		3.6.1 Defining and Creating File Systems
		3.6.2 File Storage
		3.6.3 How the Kernel Creates Files
		3.6.4 How the Kernel Accesses Files
	3.7 The ls Command
	3.8 The Directory Interface
	3.9 Implementing ls
	3.10 A Second Version of ls
		3.10.1 Adding the -l Option to ls
		3.10.2 Converting File Mode to String Format
		3.10.3 Converting User/Group ID to Strings
		3.10.4 Formatting Time
		3.10.5 Getting the Name of the Reference of a Link
	3.11 The Three Special Bits
		3.11.1 The Set-User-ID Bit
		3.11.2 The Set-Group-ID Bit
		3.11.3 The Sticky-Bit
		3.11.4 The Special Bits and ls
	3.12 A Final Version of ls
	3.13 Modifying File Attributes
		3.13.1 Type of a File
		3.13.2 Permission Bits and Special Bits
		3.13.3 Number of Links to a File
		3.13.4 Owner and Group of a File
		3.13.5 Size of a File
		3.13.6 Modification and Access Time
		3.13.7 Name of a File
	3.14 Traversing the Tree, Up and Down
	3.15 The pwd Command
		3.15.1 Implementing the pwd Command
		3.15.2 About pwd
		3.15.3 How pwd Works
		3.15.4 A First Version of pwd
		3.15.5 Multiple File Systems: Mounting
		3.15.6 Duplicate I-node Numbers and Cross-Device Links
		3.15.7 A Second Version of pwd
		3.15.8 Symbolic Links
		3.15.9 System Calls Related to Symbolic Links
	3.16 Tree Walks
		3.16.1 The nftw() Tree Walk Function
		3.16.2 The du Command
		3.16.3 The fts File Hierarchy Traversal Functions
Appendix A
	A.1 Useful Command-Line Options for ls
		A.1.1 Bit Masks
	A.2 The find Command
Control of Disk and Terminal I/O
	Overview
	Open Files
		Using fcntl() to Control File Descriptor Attributes
		Appending and Race Conditions
		Controlling the Connection When Opening a File
	Device Files
		Naming and Organizing Device Files
		Accessing Devices Via Device Files
		Device Drivers and the /dev Directory
		Disk Drivers
		Pseudo-Terminals
		Character I/O Interfaces
		Other Character Devices
		Writing to a Device File
	Terminals and Terminal I/O
		An Experiment
		Terminal Devices: An Overview
		The stty Command
		Programming the Terminal Driver
		Implementing stty: showtty
		Non-Canonical Terminal Modes
		Other Terminal Processing Modes
	I/O Control Using ioctl
	Summary
Interactive Programs and Signals
	The Different Types of UNIX Programs
		Software Tools (Filters)
		Daemons
		Interactive User Programs
	Designing Interactive User Programs
		Two Different Paradigms
		A Simple Text Editor: simplevi
			Features of simplevi
			Program Design
			Terminal Interaction
			The Main Program
		Non-Blocking Input
		Allowing Time-Outs
		A Test Program
	Signals
		Typing Ctrl-C at a Terminal
		Sources of Signals
		Signal Types
		Sending Signals
		Signal Generation and Delivery
		Signal Handling
		Putting It Together
		Weaknesses of the Signal Mechanism
		Signal Handling The "Right" Way
		Multiple Signals
		The sigaction() call
		The sigaction struct
			Example
			Example
		Creating Signal Mask Sets
		Blocking Signals Temporarily around Critical Sections
	Summary
Event Driven Programming
	Introduction
	Common Features of Event-Driven Programs
	Terminal-based Games
	The Curses (NCurses) Library
		NCurses Basics
		Screen Updating
		Building Programs
		A Core Repertoire of Functions
		Important Points About Windows and Refreshing
		A Few Simple Programs
	User Input in NCurses
	Multiple Windows in NCurses
	Adding Timing to Programs: Sleeps
	Combining User Input and Timing
	Timing with the alarm() and pause() system calls
	Interval Timers
		Three kinds of timers: Real, Virtual, and Profile
		The Initial and Repeating Values
		How Timers Are Implemented in UNIX
		Timer Limitations and Precautions
	Timers and Signals in Video Games
		Cautions About Signal Handler Design
		A Demonstration
	Non-polling Input
		Non-polling I/O Using the O_ASYNC Flag
		The bouncestr.c Program Using O_ASYNC: Flawed Version
		The bouncestr.c Program Using O_ASYNC : A Proper Solution
		The bouncestr.c Program Using AIO
		Simulating Multiple Timers
		Summary
Process Architecture and Control
	Introduction
	Examining Processes on the Command Line
	Process Groups
	Foreground and Background Processes
	Sessions
	The Memory Architecture of a Process
		Overview
		The Process Structure
		The User Structure
		The Text Segment
		The Stack Segment
		The Data Segment
		From File to Memory
		A Program To Display The Virtual Memory Boundaries
	Creating New Processes Using fork
		Other Versions of fork()
		Synchronizing Processes with Signals
	Executing Programs: The exec family
		The execve() System Call
		The exec() Library Functions
	Synchronizing Parents and Children: wait and exit
		Exit() Stage Left
		Waiting for Children to Terminate
		Using wait()
		Using waitpid()
		Non-blocking waits
		Waiting for State Changes in Children
	Summary
Interprocess Communication, Part I
	Introduction
	Unnamed Pipes
		Parent and Child Sharing a Pipe
		Atomic Writes
			More About fpathconf()
		Pipe Capacity
		Caveats and Reminders Regarding Blocking I/O and Pipes
	I/O Redirection Revisited
		Simulating Output Redirection
		Simulating the '|' Shell Operator
		The popen() Library Function
	Named Pipes
		Named Pipes at the Command Level
		Programming With Named Pipes
			Example
		An Iterative Server
		Concurrent Servers
			The Concurrent Server Client
			The Concurrent Server
	Daemon Processes
	Multiplexed I/O With select
	Summary
Interprocess Communication, Part II
	Sockets
		Background
		Connections
		Communication Basics
		The Socket InterfaceThis section must be updated. Some of the methods described are now obsolete.
		Setting Up a Connection Oriented Service
		Programming a Connection Oriented Server
		A Connection-Oriented Client Using Multiplexed I/O
Threads
	Introduction
	Thread Concepts
	Programming Using Threads
	Overview of the Pthread Library
	Thread Management
		Creating Threads
			Design Decision Regarding Shared Data
		Thread Identification
		Thread Termination
		Thread Joining and Joinability
		Detached Threads
		Thread Cancellation
		Thread Properties
			Stack Size
	Mutexes
		Introduction
		Creating and Initializing Mutexes
		Locking a Mutex
		Unlocking a Mutex
		Destroying a Mutex
		Examples Using a Normal Mutex
		Other Types of Mutexes
	Condition Variables
		Creating and Destroying Condition Variables
		Waiting on Conditions
		Waking Threads Blocked on Conditions
		Condition Attributes
		Example
	Barrier Synchronization
		Motivation
		PThreads Barriers
		Example
	Reader/Writer Locks
		Introduction
		Using Reader/Writer Locks
		Further Details
		Example
	Other Topics Not Covered