https://DevOpsCloud.io -- Cloud Monk Losang Jinpa, Ph.D., MCSE/MCT, GitOps DevOps Engineer

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Fair Use Source: B004OEJMZM-TLPI2010

BRIEF CONTENTS

• Preface

• Chapter 1: History and Standards

• Chapter 2: Fundamental Concepts

• Chapter 3: System Programming Concepts

• Chapter 4: File I/O: The Universal I/O Model

• Chapter 5: File I/O: Further Details

• Chapter 6: Processes

• Chapter 7: Memory Allocation

• Chapter 8: Users and Groups

• Chapter 9: Process Credentials

• Chapter 10: Time

• Chapter 11: System Limits and Options

• Chapter 12: System and Process Information

• Chapter 13: File I/O Buffering

• Chapter 14: File Systems

• Chapter 15: File Attributes

• Chapter 16: Extended Attributes

• Chapter 17: Access Control Lists

• Chapter 18: Directories and Links

• Chapter 19: Monitoring File Events

• Chapter 20: Signals: Fundamental Concepts

• Chapter 21: Signals: Signal Handlers

• Chapter 22: Signals: Advanced Features

• Chapter 23: Timers and Sleeping

• Chapter 24: Process Creation

• Chapter 25: Process Termination

• Chapter 26: Monitoring Child Processes

• Chapter 27: Program Execution

• Chapter 28: Process Creation and Program Execution in More Detail

• Chapter 29: Threads: Introduction

• Chapter 30: Threads: Thread Synchronization

• Chapter 31: Threads: Thread Safety and Per-Thread Storage

• Chapter 32: Threads: Thread Cancellation

• Chapter 33: Threads: Further Details

• Chapter 34: Process Groups, Sessions, and Job Control

• Chapter 35: Process Priorities and Scheduling

• Chapter 36: Process Resources

• Chapter 37: Daemons

• Chapter 38: Writing Secure Privileged Programs

• Chapter 39: Capabilities

• Chapter 40: Login Accounting

• Chapter 41: Fundamentals of Shared Libraries

• Chapter 42: Advanced Features of Shared Libraries

• Chapter 43: Interprocess Communication Overview

• Chapter 44: Pipes and FIFOs

• Chapter 45: Introduction to System V IPC

• Chapter 46: System V Message Queues

• Chapter 47: System V Semaphores

• Chapter 48: System V Shared Memory

• Chapter 49: Memory Mappings

• Chapter 50: Virtual Memory Operations

• Chapter 51: Introduction to POSIX IPC

• Chapter 52: POSIX Message Queues

• Chapter 53: POSIX Semaphores

• Chapter 54: POSIX Shared Memory

• Chapter 55: File Locking

• Chapter 56: Sockets: Introduction

• Chapter 57: Sockets: UNIX Domain

• Chapter 58: Sockets: Fundamentals of TCP/IP Networks

• Chapter 59: Sockets: Internet Domains

• Chapter 60: Sockets: Server Design

• Chapter 61: Sockets: Advanced Topics

• Chapter 62: Terminals

• Chapter 63: Alternative I/O Models

• Chapter 64: Pseudoterminals

• Appendix A: Tracing System Calls

• Appendix B: Parsing Command-Line Options

• Appendix C: Casting the NULL Pointer

• Appendix D: Kernel Configuration

• Appendix E: Further Sources of Information

• Appendix F: Solutions to Selected Exercises

• Bibliography

• Index

• CONTENTS IN DETAIL

• PREFACE

1 HISTORY AND STANDARDS

• 1.1 A Brief History of UNIX and C

• 1.2 A Brief History of Linux

• 1.2.1 The GNU Project

• 1.2.2 The Linux Kernel

• 1.3 Standardization

• 1.3.1 The C Programming Language

• 1.3.2 The First POSIX Standards

• 1.3.3 X/Open Company and The Open Group

• 1.3.4 SUSv3 and POSIX.1-2001

• 1.3.5 SUSv4 and POSIX.1-2008

• 1.3.6 UNIX Standards Timeline

• 1.3.7 Implementation Standards

• 1.3.8 Linux, Standards, and the Linux Standard Base

• 1.4 Summary

2 FUNDAMENTAL CONCEPTS

• 2.1 The Core Operating System: The Kernel

• 2.2 The Shell

• 2.3 Users and Groups

• 2.4 Single Directory Hierarchy, Directories, Links, and Files

• 2.5 File I/O Model

• 2.6 Programs

• 2.7 Processes

• 2.8 Memory Mappings

• 2.9 Static and Shared Libraries

• 2.10 Interprocess Communication and Synchronization

• 2.11 Signals

• 2.12 Threads

• 2.13 Process Groups and Shell Job Control

• 2.14 Sessions, Controlling Terminals, and Controlling Processes

• 2.15 Pseudoterminals

• 2.16 Date and Time

• 2.17 Client-Server Architecture

• 2.18 Realtime

• 2.19 The /proc File System

• 2.20 Summary

3 SYSTEM PROGRAMMING CONCEPTS

• 3.1 System Calls

• 3.2 Library Functions

• 3.3 The Standard C Library; The GNU C Library (glibc)

• 3.4 Handling Errors from System Calls and Library Functions

• 3.5 Notes on the Example Programs in This Book

• 3.5.1 Command-Line Options and Arguments

• 3.5.2 Common Functions and Header Files

• 3.6 Portability Issues

• 3.6.1 Feature Test Macros

• 3.6.2 System Data Types

• 3.6.3 Miscellaneous Portability Issues

• 3.7 Summary

• 3.8 Exercise

4 FILE I/O: THE UNIVERSAL I/O MODEL

• 4.1 Overview

• 4.2 Universality of I/O

• 4.3 Opening a File: open()

• 4.3.1 The open() flags Argument

• 4.3.2 Errors from open()

• 4.3.3 The creat() System Call

• 4.4 Reading from a File: read()

• 4.5 Writing to a File: write()

• 4.6 Closing a File: close()

• 4.7 Changing the File Offset: lseek()

• 4.8 Operations Outside the Universal I/O Model: ioctl()

• 4.9 Summary

• 4.10 Exercises

5 FILE I/O: FURTHER DETAILS

• 5.1 Atomicity and Race Conditions

• 5.2 File Control Operations: fcntl()

• 5.3 Open File Status Flags

• 5.4 Relationship Between File Descriptors and Open Files

• 5.5 Duplicating File Descriptors

• 5.6 File I/O at a Specified Offset: pread() and pwrite()

• 5.7 Scatter-Gather I/O: readv() and writev()

• 5.8 Truncating a File: truncate() and ftruncate()

• 5.9 Nonblocking I/O

• 5.10 I/O on Large Files

• 5.11 The /dev/fd Directory

• 5.12 Creating Temporary Files

• 5.13 Summary

• 5.14 Exercises

6 PROCESSES

• 6.1 Processes and Programs

• 6.2 Process ID and Parent Process ID

• 6.3 Memory Layout of a Process

• 6.4 Virtual Memory Management

• 6.5 The Stack and Stack Frames

• 6.6 Command-Line Arguments (argc, argv)

• 6.7 Environment List

• 6.8 Performing a Nonlocal Goto: setjmp() and longjmp()

• 6.9 Summary

• 6.10 Exercises

7 MEMORY ALLOCATION

• 7.1 Allocating Memory on the Heap

• 7.1.1 Adjusting the Program Break: brk() and sbrk()

• 7.1.2 Allocating Memory on the Heap: malloc() and free()

• 7.1.3 Implementation of malloc() and free()

• 7.1.4 Other Methods of Allocating Memory on the Heap

• 7.2 Allocating Memory on the Stack: alloca()

• 7.3 Summary

• 7.4 Exercises

8 USERS AND GROUPS

• 8.1 The Password File: /etc/passwd

• 8.2 The Shadow Password File: /etc/shadow

• 8.3 The Group File: /etc/group

• 8.4 Retrieving User and Group Information

• 8.5 Password Encryption and User Authentication

• 8.6 Summary

• 8.7 Exercises

9 PROCESS CREDENTIALS

• 9.1 Real User ID and Real Group ID

• 9.2 Effective User ID and Effective Group ID

• 9.3 Set-User-ID and Set-Group-ID Programs

• 9.4 Saved Set-User-ID and Saved Set-Group-ID

• 9.5 File-System User ID and File-System Group ID

• 9.6 Supplementary Group IDs

• 9.7 Retrieving and Modifying Process Credentials

• 9.7.1 Retrieving and Modifying Real, Effective, and Saved Set IDs

• 9.7.2 Retrieving and Modifying File-System IDs

• 9.7.3 Retrieving and Modifying Supplementary Group IDs

• 9.7.4 Summary of Calls for Modifying Process Credentials

• 9.7.5 Example: Displaying Process Credentials

• 9.8 Summary

• 9.9 Exercises

10 TIME

• 10.1 Calendar Time

• 10.2 Time-Conversion Functions

• 10.2.1 Converting time_t to Printable Form

• 10.2.2 Converting Between time_t and Broken-Down Time

• 10.2.3 Converting Between Broken-Down Time and Printable Form

• 10.3 Timezones

• 10.4 Locales

• 10.5 Updating the System Clock

• 10.6 The Software Clock (Jiffies)

• 10.7 Process Time

• 10.8 Summary

• 10.9 Exercise

11 SYSTEM LIMITS AND OPTIONS

• 11.1 System Limits

• 11.2 Retrieving System Limits (and Options) at Run Time

• 11.3 Retrieving File-Related Limits (and Options) at Run Time

• 11.4 Indeterminate Limits

• 11.5 System Options

• 11.6 Summary

• 11.7 Exercises

12 SYSTEM AND PROCESS INFORMATION

• 12.1 The /proc File System

• 12.1.1 Obtaining Information About a Process: /proc/PID

• 12.1.2 System Information Under /proc

• 12.1.3 Accessing /proc Files

• 12.2 System Identification: uname()

• 12.3 Summary

• 12.4 Exercises

13 FILE I/O BUFFERING

• 13.1 Kernel Buffering of File I/O: The Buffer Cache

• 13.2 Buffering in the stdio Library

• 13.3 Controlling Kernel Buffering of File I/O

• 13.4 Summary of I/O Buffering

• 13.5 Advising the Kernel About I/O Patterns

• 13.6 Bypassing the Buffer Cache: Direct I/O

• 13.7 Mixing Library Functions and System Calls for File I/O

• 13.8 Summary

• 13.9 Exercises

14 FILE SYSTEMS

• 14.1 Device Special Files (Devices)

• 14.2 Disks and Partitions

• 14.3 File Systems

• 14.4 I-nodes

• 14.5 The Virtual File System (VFS)

• 14.6 Journaling File Systems

• 14.7 Single Directory Hierarchy and Mount Points

• 14.8 Mounting and Unmounting File Systems

• 14.8.1 Mounting a File System: mount()

• 14.8.2 Unmounting a File System: umount() and umount2()

• 14.9 Advanced Mount Features

• 14.9.1 Mounting a File System at Multiple Mount Points

• 14.9.2 Stacking Multiple Mounts on the Same Mount Point

• 14.9.3 Mount Flags That Are Per-Mount Options

• 14.9.4 Bind Mounts

• 14.9.5 Recursive Bind Mounts

• 14.10 A Virtual Memory File System: tmpfs

• 14.11 Obtaining Information About a File System: statvfs()

• 14.12 Summary

• 14.13 Exercise

15 FILE ATTRIBUTES

• 15.1 Retrieving File Information: stat()

• 15.2 File Timestamps

• 15.2.1 Changing File Timestamps with utime() and utimes()

• 15.2.2 Changing File Timestamps with utimensat() and futimens()

• 15.3 File Ownership

• 15.3.1 Ownership of New Files

• 15.3.2 Changing File Ownership: chown(), fchown(), and lchown()

• 15.4 File Permissions

• 15.4.1 Permissions on Regular Files

• 15.4.2 Permissions on Directories

• 15.4.3 Permission-Checking Algorithm

• 15.4.4 Checking File Accessibility: access()

• 15.4.5 Set-User-ID, Set-Group-ID, and Sticky Bits

• 15.4.6 The Process File Mode Creation Mask: umask()

• 15.4.7 Changing File Permissions: chmod() and fchmod()

• 15.5 I-node Flags (ext2 Extended File Attributes)

• 15.6 Summary

• 15.7 Exercises

16 EXTENDED ATTRIBUTES

• 16.1 Overview

• 16.2 Extended Attribute Implementation Details

• 16.3 System Calls for Manipulating Extended Attributes

• 16.4 Summary

• 16.5 Exercise

17 ACCESS CONTROL LISTS

• 17.1 Overview

• 17.2 ACL Permission-Checking Algorithm

• 17.3 Long and Short Text Forms for ACLs

• 17.4 The ACL_MASK Entry and the ACL Group Class

• 17.5 The getfacl and setfacl Commands

• 17.6 Default ACLs and File Creation

• 17.7 ACL Implementation Limits

• 17.8 The ACL API

• 17.9 Summary

• 17.10 Exercise

18 DIRECTORIES AND LINKS

• 18.1 Directories and (Hard) Links

• 18.2 Symbolic (Soft) Links

• 18.3 Creating and Removing (Hard) Links: link() and unlink()

• 18.4 Changing the Name of a File: rename()

• 18.5 Working with Symbolic Links: symlink() and readlink()

• 18.6 Creating and Removing Directories: mkdir() and rmdir()

• 18.7 Removing a File or Directory: remove()

• 18.8 Reading Directories: opendir() and readdir()

• 18.9 File Tree Walking: nftw()

• 18.10 The Current Working Directory of a Process

• 18.11 Operating Relative to a Directory File Descriptor

• 18.12 Changing the Root Directory of a Process: chroot()

• 18.13 Resolving a Pathname: realpath()

• 18.14 Parsing Pathname Strings: dirname() and basename()

• 18.15 Summary

• 18.16 Exercises

19 MONITORING FILE EVENTS

• 19.1 Overview

• 19.2 The inotify API

• 19.3 inotify Events

• 19.4 Reading inotify Events

• 19.5 Queue Limits and /proc Files

• 19.6 An Older System for Monitoring File Events: dnotify

• 19.7 Summary

• 19.8 Exercise

20 SIGNALS: FUNDAMENTAL CONCEPTS

• 20.1 Concepts and Overview

• 20.2 Signal Types and Default Actions

• 20.3 Changing Signal Dispositions: signal()

• 20.4 Introduction to Signal Handlers

• 20.5 Sending Signals: kill()

• 20.6 Checking for the Existence of a Process

• 20.7 Other Ways of Sending Signals: raise() and killpg()

• 20.8 Displaying Signal Descriptions

• 20.9 Signal Sets

• 20.10 The Signal Mask (Blocking Signal Delivery)

• 20.11 Pending Signals

• 20.12 Signals Are Not Queued

• 20.13 Changing Signal Dispositions: sigaction()

• 20.14 Waiting for a Signal: pause()

• 20.15 Summary

• 20.16 Exercises

21 SIGNALS: SIGNAL HANDLERS

• 21.1 Designing Signal Handlers

• 21.1.1 Signals Are Not Queued (Revisited)

• 21.1.2 Reentrant and Async-Signal-Safe Functions

• 21.1.3 Global Variables and the sig_atomic_t Data Type

• 21.2 Other Methods of Terminating a Signal Handler

• 21.2.1 Performing a Nonlocal Goto from a Signal Handler

• 21.2.2 Terminating a Process Abnormally: abort()

• 21.3 Handling a Signal on an Alternate Stack: sigaltstack()

• 21.4 The SA_SIGINFO Flag

• 21.5 Interruption and Restarting of System Calls

• 21.6 Summary

• 21.7 Exercise

22 SIGNALS: ADVANCED FEATURES

• 22.1 Core Dump Files

• 22.2 Special Cases for Delivery, Disposition, and Handling

• 22.3 Interruptible and Uninterruptible Process Sleep States

• 22.4 Hardware-Generated Signals

• 22.5 Synchronous and Asynchronous Signal Generation

• 22.6 Timing and Order of Signal Delivery

• 22.7 Implementation and Portability of signal()

• 22.8 Realtime Signals

• 22.8.1 Sending Realtime Signals

• 22.8.2 Handling Realtime Signals

• 22.9 Waiting for a Signal Using a Mask: sigsuspend()

• 22.10 Synchronously Waiting for a Signal

• 22.11 Fetching Signals via a File Descriptor

• 22.12 Interprocess Communication with Signals

• 22.13 Earlier Signal APIs (System V and BSD)

• 22.14 Summary

• 22.15 Exercises

23 TIMERS AND SLEEPING

• 23.1 Interval Timers

• 23.2 Scheduling and Accuracy of Timers

• 23.3 Setting Timeouts on Blocking Operations

• 23.4 Suspending Execution for a Fixed Interval (Sleeping)

• 23.4.1 Low-Resolution Sleeping: sleep()

• 23.4.2 High-Resolution Sleeping: nanosleep()

• 23.5 POSIX Clocks

• 23.5.1 Retrieving the Value of a Clock: clock_gettime()

• 23.5.2 Setting the Value of a Clock: clock_settime()

• 23.5.3 Obtaining the Clock ID of a Specific Process or Thread

• 23.5.4 Improved High-Resolution Sleeping: clock_nanosleep()

• 23.6 POSIX Interval Timers

• 23.6.1 Creating a Timer: timer_create()

• 23.6.2 Arming and Disarming a Timer: timer_settime()

• 23.6.3 Retrieving the Current Value of a Timer: timer_gettime()

• 23.6.4 Deleting a Timer: timer_delete()

• 23.6.5 Notification via a Signal

• 23.6.6 Timer Overruns

• 23.6.7 Notification via a Thread

• 23.7 Timers That Notify via File Descriptors: The timerfd API

• 23.8 Summary

• 23.9 Exercises

24 PROCESS CREATION

• 24.1 Overview of fork(), exit(), wait(), and execve()

• 24.2 Creating a New Process: fork()

• 24.2.1 File Sharing Between Parent and Child

• 24.2.2 Memory Semantics of fork()

• 24.3 The vfork() System Call

• 24.4 Race Conditions After fork()

• 24.5 Avoiding Race Conditions by Synchronizing with Signals

• 24.6 Summary

• 24.7 Exercises

25 PROCESS TERMINATION

• 25.1 Terminating a Process: _exit() and exit()

• 25.2 Details of Process Termination

• 25.3 Exit Handlers

• 25.4 Interactions Between fork(), stdio Buffers, and _exit()

• 25.5 Summary

• 25.6 Exercise

26 MONITORING CHILD PROCESSES

• 26.1 Waiting on a Child Process

• 26.1.1 The wait() System Call

• 26.1.2 The waitpid() System Call

• 26.1.3 The Wait Status Value

• 26.1.4 Process Termination from a Signal Handler

• 26.1.5 The waitid() System Call

• 26.1.6 The wait3() and wait4() System Calls

• 26.2 Orphans and Zombies

• 26.3 The SIGCHLD Signal

• 26.3.1 Establishing a Handler for SIGCHLD

• 26.3.2 Delivery of SIGCHLD for Stopped Children

• 26.3.3 Ignoring Dead Child Processes

• 26.4 Summary

• 26.5 Exercises

27 PROGRAM EXECUTION

• 27.1 Executing a New Program: execve()

• 27.2 The exec() Library Functions

• 27.2.1 The PATH Environment Variable

• 27.2.2 Specifying Program Arguments as a List

• 27.2.3 Passing the Caller’s Environment to the New Program

• 27.2.4 Executing a File Referred to by a Descriptor: fexecve()

• 27.3 Interpreter Scripts

• 27.4 File Descriptors and exec()

• 27.5 Signals and exec()

• 27.6 Executing a Shell Command: system()

• 27.7 Implementing system()

• 27.8 Summary

• 27.9 Exercises

28 PROCESS CREATION AND PROGRAM EXECUTION IN MORE DETAIL

• 28.1 Process Accounting

• 28.2 The clone() System Call

• 28.2.1 The clone() flags Argument

• 28.2.2 Extensions to waitpid() for Cloned Children

• 28.3 Speed of Process Creation

• 28.4 Effect of exec() and fork() on Process Attributes

• 28.5 Summary

• 28.6 Exercise

29 THREADS: INTRODUCTION

• 29.1 Overview

• 29.2 Background Details of the Pthreads API

• 29.3 Thread Creation

• 29.4 Thread Termination

• 29.5 Thread IDs

• 29.6 Joining with a Terminated Thread

• 29.7 Detaching a Thread

• 29.8 Thread Attributes

• 29.9 Threads Versus Processes

• 29.10 Summary

• 29.11 Exercises

30 THREADS: THREAD SYNCHRONIZATION

• 30.1 Protecting Accesses to Shared Variables: Mutexes

• 30.1.1 Statically Allocated Mutexes

• 30.1.2 Locking and Unlocking a Mutex

• 30.1.3 Performance of Mutexes

• 30.1.4 Mutex Deadlocks

• 30.1.5 Dynamically Initializing a Mutex

• 30.1.6 Mutex Attributes

• 30.1.7 Mutex Types

• 30.2 Signaling Changes of State: Condition Variables

• 30.2.1 Statically Allocated Condition Variables

• 30.2.2 Signaling and Waiting on Condition Variables

• 30.2.3 Testing a Condition Variable’s Predicate

• 30.2.4 Example Program: Joining Any Terminated Thread

• 30.2.5 Dynamically Allocated Condition Variables

• 30.3 Summary

• 30.4 Exercises

31 THREADS: THREAD SAFETY AND PER-THREAD STORAGE

• 31.1 Thread Safety (and Reentrancy Revisited)

• 31.2 One-Time Initialization

• 31.3 Thread-Specific Data

• 31.3.1 Thread-Specific Data from the Library Function’s Perspective

• 31.3.2 Overview of the Thread-Specific Data API

• 31.3.3 Details of the Thread-Specific Data API

• 31.3.4 Employing the Thread-Specific Data API

• 31.3.5 Thread-Specific Data Implementation Limits

• 31.4 Thread-Local Storage

• 31.5 Summary

• 31.6 Exercises

32 THREADS: THREAD CANCELLATION

• 32.1 Canceling a Thread

• 32.2 Cancellation State and Type

• 32.3 Cancellation Points

• 32.4 Testing for Thread Cancellation

• 32.5 Cleanup Handlers

• 32.6 Asynchronous Cancelability

• 32.7 Summary

33 THREADS: FURTHER DETAILS

• 33.1 Thread Stacks

• 33.2 Threads and Signals

• 33.2.1 How the UNIX Signal Model Maps to Threads

• 33.2.2 Manipulating the Thread Signal Mask

• 33.2.3 Sending a Signal to a Thread

• 33.2.4 Dealing with Asynchronous Signals Sanely

• 33.3 Threads and Process Control

• 33.4 Thread Implementation Models

• 33.5 Linux Implementations of POSIX Threads

• 33.5.1 LinuxThreads

• 33.5.2 NPTL

• 33.5.3 Which Threading Implementation?

• 33.6 Advanced Features of the Pthreads API

• 33.7 Summary

• 33.8 Exercises

34 PROCESS GROUPS, SESSIONS, AND JOB CONTROL

• 34.1 Overview

• 34.2 Process Groups

• 34.3 Sessions

• 34.4 Controlling Terminals and Controlling Processes

• 34.5 Foreground and Background Process Groups

• 34.6 The SIGHUP Signal

• 34.6.1 Handling of SIGHUP by the Shell

• 34.6.2 SIGHUP and Termination of the Controlling Process

• 34.7 Job Control

• 34.7.1 Using Job Control Within the Shell

• 34.7.2 Implementing Job Control

• 34.7.3 Handling Job-Control Signals

• 34.7.4 Orphaned Process Groups (and SIGHUP Revisited)

• 34.8 Summary

• 34.9 Exercises

35 PROCESS PRIORITIES AND SCHEDULING

• 35.1 Process Priorities (Nice Values)

• 35.2 Overview of Realtime Process Scheduling

• 35.2.1 The SCHED_RR Policy

• 35.2.2 The SCHED_FIFO Policy

• 35.2.3 The SCHED_BATCH and SCHED_IDLE Policies

• 35.3 Realtime Process Scheduling API

• 35.3.1 Realtime Priority Ranges

• 35.3.2 Modifying and Retrieving Policies and Priorities

• 35.3.3 Relinquishing the CPU

• 35.3.4 The SCHED_RR Time Slice

• 35.4 CPU Affinity

• 35.5 Summary

• 35.6 Exercises

36 PROCESS RESOURCES

• 36.1 Process Resource Usage

• 36.2 Process Resource Limits

• 36.3 Details of Specific Resource Limits

• 36.4 Summary

• 36.5 Exercises

37 DAEMONS

• 37.1 Overview

• 37.2 Creating a Daemon

• 37.3 Guidelines for Writing Daemons

• 37.4 Using SIGHUP to Reinitialize a Daemon

• 37.5 Logging Messages and Errors Using syslog

• 37.5.1 Overview

• 37.5.2 The syslog API

• 37.5.3 The /etc/syslog.conf File

• 37.6 Summary

• 37.7 Exercise

38 WRITING SECURE PRIVILEGED PROGRAMS

• 38.1 Is a Set-User-ID or Set-Group-ID Program Required?

• 38.2 Operate with Least Privilege

• 38.3 Be Careful When Executing a Program

• 38.4 Avoid Exposing Sensitive Information

• 38.5 Confine the Process

• 38.6 Beware of Signals and Race Conditions

• 38.7 Pitfalls When Performing File Operations and File I/O

• 38.8 Don’t Trust Inputs or the Environment

• 38.9 Beware of Buffer Overruns

• 38.10 Beware of Denial-of-Service Attacks

• 38.11 Check Return Statuses and Fail Safely

• 38.12 Summary

• 38.13 Exercises

39 CAPABILITIES

• 39.1 Rationale for Capabilities

• 39.2 The Linux Capabilities

• 39.3 Process and File Capabilities

• 39.3.1 Process Capabilities

• 39.3.2 File Capabilities

• 39.3.3 Purpose of the Process Permitted and Effective Capability Sets

• 39.3.4 Purpose of the File Permitted and Effective Capability Sets

• 39.3.5 Purpose of the Process and File Inheritable Sets

• 39.3.6 Assigning and Viewing File Capabilities from the Shell

• 39.4 The Modern Capabilities Implementation

• 39.5 Transformation of Process Capabilities During exec()

• 39.5.1 Capability Bounding Set

• 39.5.2 Preserving root Semantics

• 39.6 Effect on Process Capabilities of Changing User IDs

• 39.7 Changing Process Capabilities Programmatically

• 39.8 Creating Capabilities-Only Environments

• 39.9 Discovering the Capabilities Required by a Program

• 39.10 Older Kernels and Systems Without File Capabilities

• 39.11 Summary

• 39.12 Exercise

40 LOGIN ACCOUNTING

• 40.1 Overview of the utmp and wtmp Files

• 40.2 The utmpx API

• 40.3 The utmpx Structure

• 40.4 Retrieving Information from the utmp and wtmp Files

• 40.5 Retrieving the Login Name: getlogin()

• 40.6 Updating the utmp and wtmp Files for a Login Session

• 40.7 The lastlog File

• 40.8 Summary

• 40.9 Exercises

41 FUNDAMENTALS OF SHARED LIBRARIES

• 41.1 Object Libraries

• 41.2 Static Libraries

• 41.3 Overview of Shared Libraries

• 41.4 Creating and Using Shared Libraries—A First Pass

• 41.4.1 Creating a Shared Library

• 41.4.2 Position-Independent Code

• 41.4.3 Using a Shared Library

• 41.4.4 The Shared Library Soname

• 41.5 Useful Tools for Working with Shared Libraries

• 41.6 Shared Library Versions and Naming Conventions

• 41.7 Installing Shared Libraries

• 41.8 Compatible Versus Incompatible Libraries

• 41.9 Upgrading Shared Libraries

• 41.10 Specifying Library Search Directories in an Object File

• 41.11 Finding Shared Libraries at Run Time

• 41.12 Run-Time Symbol Resolution

• 41.13 Using a Static Library Instead of a Shared Library

• 41.14 Summary

• 41.15 Exercise

42 ADVANCED FEATURES OF SHARED LIBRARIES

• 42.1 Dynamically Loaded Libraries

• 42.1.1 Opening a Shared Library: dlopen()

• 42.1.2 Diagnosing Errors: dlerror()

• 42.1.3 Obtaining the Address of a Symbol: dlsym()

• 42.1.4 Closing a Shared Library: dlclose()

• 42.1.5 Obtaining Information About Loaded Symbols: dladdr()

• 42.1.6 Accessing Symbols in the Main Program

• 42.2 Controlling Symbol Visibility

• 42.3 Linker Version Scripts

• 42.3.1 Controlling Symbol Visibility with Version Scripts

• 42.3.2 Symbol Versioning

• 42.4 Initialization and Finalization Functions

• 42.5 Preloading Shared Libraries

• 42.6 Monitoring the Dynamic Linker: LD_DEBUG

• 42.7 Summary

• 42.8 Exercises

43 INTERPROCESS COMMUNICATION OVERVIEW

• 43.1 A Taxonomy of IPC Facilities

• 43.2 Communication Facilities

• 43.3 Synchronization Facilities

• 43.4 Comparing IPC Facilities

• 43.5 Summary

• 43.6 Exercises

44 PIPES AND FIFOS

• 44.1 Overview

• 44.2 Creating and Using Pipes

• 44.3 Pipes as a Method of Process Synchronization

• 44.4 Using Pipes to Connect Filters

• 44.5 Talking to a Shell Command via a Pipe: popen()

• 44.6 Pipes and stdio Buffering

• 44.7 FIFOs

• 44.8 A Client-Server Application Using FIFOs

• 44.9 Nonblocking I/O

• 44.10 Semantics of read() and write() on Pipes and FIFOs

• 44.11 Summary

• 44.12 Exercises

45 INTRODUCTION TO SYSTEM V IPC

• 45.1 API Overview

• 45.2 IPC Keys

• 45.3 Associated Data Structure and Object Permissions

• 45.4 IPC Identifiers and Client-Server Applications

• 45.5 Algorithm Employed by System V IPC get Calls

• 45.6 The ipcs and ipcrm Commands

• 45.7 Obtaining a List of All IPC Objects

• 45.8 IPC Limits

• 45.9 Summary

• 45.10 Exercises

46 SYSTEM V MESSAGE QUEUES

• 46.1 Creating or Opening a Message Queue

• 46.2 Exchanging Messages

• 46.2.1 Sending Messages

• 46.2.2 Receiving Messages

• 46.3 Message Queue Control Operations

• 46.4 Message Queue Associated Data Structure

• 46.5 Message Queue Limits

• 46.6 Displaying All Message Queues on the System

• 46.7 Client-Server Programming with Message Queues

• 46.8 A File-Server Application Using Message Queues

• 46.9 Disadvantages of System V Message Queues

• 46.10 Summary

• 46.11 Exercises

47 SYSTEM V SEMAPHORES

• 47.1 Overview

• 47.2 Creating or Opening a Semaphore Set

• 47.3 Semaphore Control Operations

• 47.4 Semaphore Associated Data Structure

• 47.5 Semaphore Initialization

• 47.6 Semaphore Operations

• 47.7 Handling of Multiple Blocked Semaphore Operations

• 47.8 Semaphore Undo Values

• 47.9 Implementing a Binary Semaphores Protocol

• 47.10 Semaphore Limits

• 47.11 Disadvantages of System V Semaphores

• 47.12 Summary

• 47.13 Exercises

48 SYSTEM V SHARED MEMORY

• 48.1 Overview

• 48.2 Creating or Opening a Shared Memory Segment

• 48.3 Using Shared Memory

• 48.4 Example: Transferring Data via Shared Memory

• 48.5 Location of Shared Memory in Virtual Memory

• 48.6 Storing Pointers in Shared Memory

• 48.7 Shared Memory Control Operations

• 48.8 Shared Memory Associated Data Structure

• 48.9 Shared Memory Limits

• 48.10 Summary

• 48.11 Exercises

49 MEMORY MAPPINGS

• 49.1 Overview

• 49.2 Creating a Mapping: mmap()

• 49.3 Unmapping a Mapped Region: munmap()

• 49.4 File Mappings

• 49.4.1 Private File Mappings

• 49.4.2 Shared File Mappings

• 49.4.3 Boundary Cases

• 49.4.4 Memory Protection and File Access Mode Interactions

• 49.5 Synchronizing a Mapped Region: msync()

• 49.6 Additional mmap() Flags

• 49.7 Anonymous Mappings

• 49.8 Remapping a Mapped Region: mremap()

• 49.9 MAP_NORESERVE and Swap Space Overcommitting

• 49.10 The MAP_FIXED Flag

• 49.11 Nonlinear Mappings: remap_file_pages()

• 49.12 Summary

• 49.13 Exercises

50 VIRTUAL MEMORY OPERATIONS

• 50.1 Changing Memory Protection: mprotect()

• 50.2 Memory Locking: mlock() and mlockall()

• 50.3 Determining Memory Residence: mincore()

• 50.4 Advising Future Memory Usage Patterns: madvise()

• 50.5 Summary

• 50.6 Exercises

51 INTRODUCTION TO POSIX IPC

• 51.1 API Overview

• 51.2 Comparison of System V IPC and POSIX IPC

• 51.3 Summary

52 POSIX MESSAGE QUEUES

• 52.1 Overview

• 52.2 Opening, Closing, and Unlinking a Message Queue

• 52.3 Relationship Between Descriptors and Message Queues

• 52.4 Message Queue Attributes

• 52.5 Exchanging Messages

• 52.5.1 Sending Messages

• 52.5.2 Receiving Messages

• 52.5.3 Sending and Receiving Messages with a Timeout

• 52.6 Message Notification

• 52.6.1 Receiving Notification via a Signal

• 52.6.2 Receiving Notification via a Thread

• 52.7 Linux-Specific Features

• 52.8 Message Queue Limits

• 52.9 Comparison of POSIX and System V Message Queues

• 52.10 Summary

• 52.11 Exercises

53 POSIX SEMAPHORES

• 53.1 Overview

• 53.2 Named Semaphores

• 53.2.1 Opening a Named Semaphore

• 53.2.2 Closing a Semaphore

• 53.2.3 Removing a Named Semaphore

• 53.3 Semaphore Operations

• 53.3.1 Waiting on a Semaphore

• 53.3.2 Posting a Semaphore

• 53.3.3 Retrieving the Current Value of a Semaphore

• 53.4 Unnamed Semaphores

• 53.4.1 Initializing an Unnamed Semaphore

• 53.4.2 Destroying an Unnamed Semaphore

• 53.5 Comparisons with Other Synchronization Techniques

• 53.6 Semaphore Limits

• 53.7 Summary

• 53.8 Exercises

54 POSIX SHARED MEMORY

• 54.1 Overview

• 54.2 Creating Shared Memory Objects

• 54.3 Using Shared Memory Objects

• 54.4 Removing Shared Memory Objects

• 54.5 Comparisons Between Shared Memory APIs

• 54.6 Summary

• 54.7 Exercise

55 FILE LOCKING

• 55.1 Overview

• 55.2 File Locking with flock()

• 55.2.1 Semantics of Lock Inheritance and Release

• 55.2.2 Limitations of flock()

• 55.3 Record Locking with fcntl()

• 55.3.1 Deadlock

• 55.3.2 Example: An Interactive Locking Program

• 55.3.3 Example: A Library of Locking Functions

• 55.3.4 Lock Limits and Performance

• 55.3.5 Semantics of Lock Inheritance and Release

• 55.3.6 Lock Starvation and Priority of Queued Lock Requests

• 55.4 Mandatory Locking

• 55.5 The /proc/locks File

• 55.6 Running Just One Instance of a Program

• 55.7 Older Locking Techniques

• 55.8 Summary

• 55.9 Exercises

56 SOCKETS: INTRODUCTION

• 56.1 Overview

• 56.2 Creating a Socket: socket()

• 56.3 Binding a Socket to an Address: bind()

• 56.4 Generic Socket Address Structures: struct sockaddr

• 56.5 Stream Sockets

• 56.5.1 Listening for Incoming Connections: listen()

• 56.5.2 Accepting a Connection: accept()

• 56.5.3 Connecting to a Peer Socket: connect()

• 56.5.4 I/O on Stream Sockets

• 56.5.5 Connection Termination: close()

• 56.6 Datagram Sockets

• 56.6.1 Exchanging Datagrams: recvfrom() and sendto()

• 56.6.2 Using connect() with Datagram Sockets

• 56.7 Summary

57 SOCKETS: UNIX DOMAIN

• 57.1 UNIX Domain Socket Addresses: struct sockaddr_un

• 57.2 Stream Sockets in the UNIX Domain

• 57.3 Datagram Sockets in the UNIX Domain

• 57.4 UNIX Domain Socket Permissions

• 57.5 Creating a Connected Socket Pair: socketpair()

• 57.6 The Linux Abstract Socket Namespace

• 57.7 Summary

• 57.8 Exercises

58 SOCKETS: FUNDAMENTALS OF TCP/IP NETWORKS

• 58.1 Internets

• 58.2 Networking Protocols and Layers

• 58.3 The Data-Link Layer

• 58.4 The Network Layer: IP

• 58.5 IP Addresses

• 58.6 The Transport Layer

• 58.6.1 Port Numbers

• 58.6.2 User Datagram Protocol (UDP)

• 58.6.3 Transmission Control Protocol (TCP)

• 58.7 Requests for Comments (RFCs)

• 58.8 Summary

59 SOCKETS: INTERNET DOMAINS

• 59.1 Internet Domain Sockets

• 59.2 Network Byte Order

• 59.3 Data Representation

• 59.4 Internet Socket Addresses

• 59.5 Overview of Host and Service Conversion Functions

• 59.6 The inet_pton() and inet_ntop() Functions

• 59.7 Client-Server Example (Datagram Sockets)

• 59.8 Domain Name System (DNS)

• 59.9 The /etc/services File

• 59.10 Protocol-Independent Host and Service Conversion

• 59.10.1 The getaddrinfo() Function

• 59.10.2 Freeing addrinfo Lists: freeaddrinfo()

• 59.10.3 Diagnosing Errors: gai_strerror()

• 59.10.4 The getnameinfo() Function

• 59.11 Client-Server Example (Stream Sockets)

• 59.12 An Internet Domain Sockets Library

• 59.13 Obsolete APIs for Host and Service Conversions

• 59.13.1 The inet_aton() and inet_ntoa() Functions

• 59.13.2 The gethostbyname() and gethostbyaddr() Functions

• 59.13.3 The getservbyname() and getservbyport() Functions

• 59.14 UNIX Versus Internet Domain Sockets

• 59.15 Further Information

• 59.16 Summary

• 59.17 Exercises

60 SOCKETS: SERVER DESIGN

• 60.1 Iterative and Concurrent Servers

• 60.2 An Iterative UDP echo Server

• 60.3 A Concurrent TCP echo Server

• 60.4 Other Concurrent Server Designs

• 60.5 The inetd (Internet Superserver) Daemon

• 60.6 Summary

• 60.7 Exercises

61 SOCKETS: ADVANCED TOPICS

• 61.1 Partial Reads and Writes on Stream Sockets

• 61.2 The shutdown() System Call

• 61.3 Socket-Specific I/O System Calls: recv() and send()

• 61.4 The sendfile() System Call

• 61.5 Retrieving Socket Addresses

• 61.6 A Closer Look at TCP

• 61.6.1 Format of a TCP Segment

• 61.6.2 TCP Sequence Numbers and Acknowledgements

• 61.6.3 TCP State Machine and State Transition Diagram

• 61.6.4 TCP Connection Establishment

• 61.6.5 TCP Connection Termination

• 61.6.6 Calling shutdown() on a TCP Socket

• 61.6.7 The TIME_WAIT State

• 61.7 Monitoring Sockets: netstat

• 61.8 Using tcpdump to Monitor TCP Traffic

• 61.9 Socket Options

• 61.10 The SO_REUSEADDR Socket Option

• 61.11 Inheritance of Flags and Options Across accept()

• 61.12 TCP Versus UDP

• 61.13 Advanced Features

• 61.13.1 Out-of-Band Data

• 61.13.2 The sendmsg() and recvmsg() System Calls

• 61.13.3 Passing File Descriptors

• 61.13.4 Receiving Sender Credentials

• 61.13.5 Sequenced-Packet Sockets

• 61.13.6 SCTP and DCCP Transport-Layer Protocols

• 61.14 Summary

• 61.15 Exercises

62 TERMINALS

• 62.1 Overview

• 62.2 Retrieving and Modifying Terminal Attributes

• 62.3 The stty Command

• 62.4 Terminal Special Characters

• 62.5 Terminal Flags

• 62.6 Terminal I/O Modes

• 62.6.1 Canonical Mode

• 62.6.2 Noncanonical Mode

• 62.6.3 Cooked, Cbreak, and Raw Modes

• 62.7 Terminal Line Speed (Bit Rate)

• 62.8 Terminal Line Control

• 62.9 Terminal Window Size

• 62.10 Terminal Identification

• 62.11 Summary

• 62.12 Exercises

63 ALTERNATIVE I/O MODELS

• 63.1 Overview

• 63.1.1 Level-Triggered and Edge-Triggered Notification

• 63.1.2 Employing Nonblocking I/O with Alternative I/O Models

• 63.2 I/O Multiplexing

• 63.2.1 The select() System Call

• 63.2.2 The poll() System Call

• 63.2.3 When Is a File Descriptor Ready?

• 63.2.4 Comparison of select() and poll()

• 63.2.5 Problems with select() and poll()

• 63.3 Signal-Driven I/O

• 63.3.1 When Is “I/O Possible” Signaled?

• 63.3.2 Refining the Use of Signal-Driven I/O

• 63.4 The epoll API

• 63.4.1 Creating an epoll Instance: epoll_create()

• 63.4.2 Modifying the epoll Interest List: epoll_ctl()

• 63.4.3 Waiting for Events: epoll_wait()

• 63.4.4 A Closer Look at epoll Semantics

• 63.4.5 Performance of epoll Versus I/O Multiplexing

• 63.4.6 Edge-Triggered Notification

• 63.5 Waiting on Signals and File Descriptors

• 63.5.1 The pselect() System Call

• 63.5.2 The Self-Pipe Trick

• 63.6 Summary

• 63.7 Exercises

64 PSEUDOTERMINALS

• 64.1 Overview

• 64.2 UNIX 98 Pseudoterminals

• 64.2.1 Opening an Unused Master: posix_openpt()

• 64.2.2 Changing Slave Ownership and Permissions: grantpt()

• 64.2.3 Unlocking the Slave: unlockpt()

• 64.2.4 Obtaining the Name of the Slave: ptsname()

• 64.3 Opening a Master: ptyMasterOpen()

• 64.4 Connecting Processes with a Pseudoterminal: ptyFork()

• 64.5 Pseudoterminal I/O

• 64.6 Implementing script(1)

• 64.7 Terminal Attributes and Window Size

• 64.8 BSD Pseudoterminals

• 64.9 Summary

• 64.10 Exercises

A TRACING SYSTEM CALLS

B PARSING COMMAND-LINE OPTIONS

C CASTING THE NULL POINTER

D KERNEL CONFIGURATION

E FURTHER SOURCES OF INFORMATION

F SOLUTIONS TO SELECTED EXERCISES

BIBLIOGRAPHY

INDEX

Fair Use Sources:

• B004OEJMZM-TLPI2010