Table Of ContentThe Linux Programming Interface
Table of Contents
Praise for The Linux Programming Interface
Preface
1. History and Standards
A Brief History of UNIX and C
A Brief History of Linux
The GNU Project
The Linux Kernel
Standardization
The C Programming Language
The First POSIX Standards
X/Open Company and The Open Group
SUSv3 and POSIX.1-2001
SUSv4 and POSIX.1-2008
UNIX Standards Timeline
Implementation Standards
Linux, Standards, and the Linux Standard Base
Summary
2. Fundamental Concepts
The Core Operating System: The Kernel
The Shell
Users and Groups
Single Directory Hierarchy, Directories, Links, and Files
File I/O Model
Programs
Processes
Memory Mappings
Static and Shared Libraries
Interprocess Communication and Synchronization
Signals
Threads
Process Groups and Shell Job Control
Sessions, Controlling Terminals, and Controlling Processes
Pseudoterminals
Date and Time
Client-Server Architecture
Realtime
The /proc File System
Summary
3. System Programming Concepts
System Calls
Library Functions
The Standard C Library; The GNU C Library (glibc)
Handling Errors from System Calls and Library Functions
Notes on the Example Programs in This Book
Command-Line Options and Arguments
Common Functions and Header Files
Portability Issues
Feature Test Macros
System Data Types
Miscellaneous Portability Issues
Summary
Exercise
4. File I/O: The Universal I/O Model
Overview
Universality of I/O
Opening a File: open()
The open() flags Argument
Errors from open()
The creat() System Call
Reading from a File: read()
Writing to a File: write()
Closing a File: close()
Changing the File Offset: lseek()
Operations Outside the Universal I/O Model: ioctl()
Summary
Exercises
5. File I/O: Further Details
Atomicity and Race Conditions
File Control Operations: fcntl()
Open File Status Flags
Relationship Between File Descriptors and Open Files
Duplicating File Descriptors
File I/O at a Specified Offset: pread() and pwrite()
Scatter-Gather I/O: readv() and writev()
Truncating a File: truncate() and ftruncate()
Nonblocking I/O
I/O on Large Files
The devfd Directory
Creating Temporary Files
Summary
Exercises
6. Processes
Processes and Programs
Process ID and Parent Process ID
Memory Layout of a Process
Virtual Memory Management
The Stack and Stack Frames
Command-Line Arguments (argc, argv)
Environment List
Accessing the environment from a program
Performing a Nonlocal Goto: setjmp() and long jmp()
Summary
Exercises
7. Memory Allocation
Allocating Memory on the Heap
Adjusting the Program Break: brk() and sbrk()
Allocating Memory on the Heap: malloc() and free()
Implementation of malloc() and free()
Other Methods of Allocating Memory on the Heap
Allocating Memory on the Stack: alloca()
Summary
Exercises
8. Users and Groups
The Password File: etcpasswd
The Shadow Password File: etcshadow
The Group File: etcgroup
Retrieving User and Group Information
Password Encryption and User Authentication
Summary
Exercises
9. Process Credentials
Real User ID and Real Group ID
Effective User ID and Effective Group ID
Set-User-ID and SetGroup-ID Programs
Saved Set-User-ID and Saved SetGroup-ID
FileSystem User ID and FileSystem Group ID
Supplementary Group IDs
Retrieving and Modifying Process Credentials
Retrieving and Modifying Real, Effective, and Saved Set IDs
Retrieving and Modifying FileSystem IDs
Retrieving and Modifying Supplementary Group IDs
Summary of Calls for Modifying Process Credentials
Example: Displaying Process Credentials
Summary
Exercises
10. Time
Calendar Time
Time-Conversion Functions
Converting time_t to Printable Form
Converting Between time_t and Broken-Down Time
Converting Between Broken-Down Time and Printable Form
Timezones
Locales
Updating the System Clock
The Software Clock (Jiffies)
Process Time
Summary
Exercise
11. System Limits and Options
System Limits
Retrieving System Limits (and Options) at Run Time
Retrieving File-Related Limits (and Options) at Run Time
Indeterminate Limits
System Options
Summary
Exercises
12. System and Process Information
The /proc File System
Obtaining Information About a Process: procPID
System Information Under /proc
Accessing /proc Files
System Identification: uname()
Summary
Exercises
13. File I/O Buffering
Kernel Buffering of File I/O: The Buffer Cache
Buffering in the stdio Library
Controlling Kernel Buffering of File I/O
Summary of I/O Buffering
Advising the Kernel About I/O Patterns
Bypassing the Buffer Cache: Direct I/O
Mixing Library Functions and System Calls for File I/O
Summary
Exercises
14. File Systems
Device Special Files (Devices)
Disks and Partitions
File Systems
I-nodes
The Virtual File System (VFS)
Journaling File Systems
Single Directory Hierarchy and Mount Points
Mounting and Unmounting File Systems
Mounting a File System: mount()
Unmounting a File System: umount() and umount2()
Advanced Mount Features
Mounting a File System at Multiple Mount Points
Stacking Multiple Mounts on the Same Mount Point
Mount Flags That Are Per-Mount Options
Bind Mounts
Recursive Bind Mounts
A Virtual Memory File System: tmpfs
Obtaining Information About a File System: statvfs()
Summary
Exercise
15. File Attributes
Retrieving File Information: stat()
File Timestamps
Changing File Timestamps with utime() and utimes()
Changing File Timestamps with utimensat() and futimens()
File Ownership
Ownership of New Files
Changing File Ownership: chown(), fchown(), and lchown()
File Permissions
Permissions on Regular Files
Permissions on Directories
Permission-Checking Algorithm
Checking File Accessibility: access()
Set-User-ID, SetGroup-ID, and Sticky Bits
The Process File Mode Creation Mask: umask()
Changing File Permissions: chmod() and fchmod()
I-node Flags (ext2 Extended File Attributes)
Summary
Exercises
16. Extended Attributes
Overview
Extended Attribute Implementation Details
System Calls for Manipulating Extended Attributes
Summary
Exercise
17. Access Control Lists
Overview
ACL Permission-Checking Algorithm
Long and Short Text Forms for ACLs
The ACL_MASK Entry and the ACL Group Class
The getfacl and setfacl Commands
Default ACLs and File Creation
ACL Implementation Limits
The ACL API
Summary
Exercise
18. Directories and Links
Directories and (Hard) Links
Symbolic (Soft) Links
Creating and Removing (Hard) Links: link() and unlink()
Changing the Name of a File: rename()
Working with Symbolic Links: symlink() and readlink()
Creating and Removing Directories: mkdir() and rmdir()
Removing a File or Directory: remove()
Reading Directories: opendir() and readdir()
File Tree Walking: nftw()
The Current Working Directory of a Process
Operating Relative to a Directory File Descriptor
Changing the Root Directory of a Process: chroot()
Resolving a Pathname: realpath()
Parsing Pathname Strings: dirname() and basename()
Summary
Exercises
19. Monitoring File Events
Overview
The inotify API
inotify Events
Reading inotify Events
Queue Limits and /proc Files
An Older System for Monitoring File Events: dnotify
Summary
Exercise
20. Signals: Fundamental Concepts
Concepts and Overview
Signal Types and Default Actions
Changing Signal Dispositions: signal()
Introduction to Signal Handlers
Sending Signals: kill()
Checking for the Existence of a Process
Other Ways of Sending Signals: raise() and killpg()
Displaying Signal Descriptions
Signal Sets
The Signal Mask (Blocking Signal Delivery)
Pending Signals
Signals Are Not Queued
Changing Signal Dispositions: sigaction()
Waiting for a Signal: pause()
Summary
Exercises
21. Signals: Signal Handlers
Designing Signal Handlers
Signals Are Not Queued (Revisited)
Reentrant and Async-Signal-Safe Functions
Global Variables and the sig_atomic_t Data Type
Other Methods of Terminating a Signal Handler
Performing a Nonlocal Goto from a Signal Handler
Terminating a Process Abnormally: abort()
Handling a Signal on an Alternate Stack: sigaltstack()
The SA_SIGINFO Flag
Interruption and Restarting of System Calls
Summary
Exercise
22. Signals: Advanced Features
Core Dump Files
Special Cases for Delivery, Disposition, and Handling
Interruptible and Uninterruptible Process Sleep States
Hardware-Generated Signals
Synchronous and Asynchronous Signal Generation
Timing and Order of Signal Delivery
Implementation and Portability of signal()
Realtime Signals
Sending Realtime Signals
Handling Realtime Signals
Waiting for a Signal Using a Mask: sigsuspend()
Synchronously Waiting for a Signal
Fetching Signals via a File Descriptor
Interprocess Communication with Signals
Earlier Signal APIs (System V and BSD)
Summary
Exercises
23. Timers and Sleeping
Interval Timers
Scheduling and Accuracy of Timers
Setting Timeouts on Blocking Operations
Suspending Execution for a Fixed Interval (Sleeping)
Low-Resolution Sleeping: sleep()
High-Resolution Sleeping: nanosleep()
POSIX Clocks
Retrieving the Value of a Clock: clock_gettime()
Setting the Value of a Clock: clock_settime()
Obtaining the Clock ID of a Specific Process or Thread
Improved High-Resolution Sleeping: clock_nanosleep()
POSIX Interval Timers
Creating a Timer: timer_create()
Arming and Disarming a Timer: timer_settime()
Retrieving the Current Value of a Timer: timer_gettime()
Deleting a Timer: timer_delete()
Notification via a Signal
Timer Overruns
Notification via a Thread
Timers That Notify via File Descriptors: The timerfd API
Summary
Exercises
24. Process Creation
Overview of fork(), exit(), wait(), and execve()
Creating a New Process: fork()
File Sharing Between Parent and Child
Memory Semantics of fork()
The vfork() System Call
Race Conditions After fork()
Avoiding Race Conditions by Synchronizing with Signals
Summary
Exercises
25. Process Termination
Terminating a Process: _exit() and exit()
Details of Process Termination
Exit Handlers
Interactions Between fork(), stdio Buffers, and _exit()
Summary
Exercise
26. Monitoring Child Processes
Waiting on a Child Process
The wait() System Call
The waitpid() System Call
The Wait Status Value
Process Termination from a Signal Handler
The waitid() System Call
The wait3() and wait4() System Calls
Orphans and Zombies
The SIGCHLD Signal
Establishing a Handler for SIGCHLD
Delivery of SIGCHLD for Stopped Children
Ignoring Dead Child Processes
Summary
Exercises
27. Program Execution
Executing a New Program: execve()
The exec() Library Functions
The PATH Environment Variable
Specifying Program Arguments as a List
Passing the Caller’s Environment to the New Program
Executing a File Referred to by a Descriptor: fexecve()
Interpreter Scripts
File Descriptors and exec()
Signals and exec()
Executing a Shell Command: system()
Implementing system()
Summary
Exercises
28. Process Creation and Program Execution in More Detail
Process Accounting
The clone() System Call
The clone() flags Argument
Extensions to waitpid() for Cloned Children
Speed of Process Creation
Effect of exec() and fork() on Process Attributes
Summary
Exercise
29. Threads: Introduction
Overview
Background Details of the Pthreads API
Thread Creation
Thread Termination
Thread IDs
Joining with a Terminated Thread
Detaching a Thread
Thread Attributes
Threads Versus Processes
Summary
Exercises
30. Threads: Thread Synchronization
Protecting Accesses to Shared Variables: Mutexes
Statically Allocated Mutexes
Locking and Unlocking a Mutex
Performance of Mutexes
Mutex Deadlocks
Dynamically Initializing a Mutex
Mutex Attributes
Mutex Types
Signaling Changes of State: Condition Variables
Statically Allocated Condition Variables
Signaling and Waiting on Condition Variables
Testing a Condition Variable’s Predicate
Example Program: Joining Any Terminated Thread
Dynamically Allocated Condition Variables
Summary
Exercises
31. Threads: Thread Safety and PerThread Storage
Thread Safety (and Reentrancy Revisited)
One-Time Initialization
Thread-Specific Data
Thread-Specific Data from the Library Function’s Perspective
Overview of the Thread-Specific Data API
Details of the Thread-Specific Data API
Employing the Thread-Specific Data API
Thread-Specific Data Implementation Limits
Thread-Local Storage
Summary
Exercises
32. Threads: Thread Cancellation
Canceling a Thread
Cancellation State and Type
Cancellation Points
Testing for Thread Cancellation
Cleanup Handlers
Asynchronous Cancelability
Summary
33. Threads: Further Details
Thread Stacks
Threads and Signals
How the UNIX Signal Model Maps to Threads
Manipulating the Thread Signal Mask
Sending a Signal to a Thread
Dealing with Asynchronous Signals Sanely
Threads and Process Control
Thread Implementation Models
Linux Implementations of POSIX Threads
LinuxThreads
NPTL
Which Threading Implementation?
Advanced Features of the Pthreads API
Summary
Exercises
34. Process Groups, Sessions, and Job Control
Overview
Process Groups
Sessions
Controlling Terminals and Controlling Processes
Foreground and Background Process Groups
The SIGHUP Signal
Handling of SIGHUP by the Shell
SIGHUP and Termination of the Controlling Process
Job Control
Using Job Control Within the Shell
Implementing Job Control
Handling Job-Control Signals
Orphaned Process Groups (and SIGHUP Revisited)
Summary
Exercises
35. Process Priorities and Scheduling
Process Priorities (Nice Values)
Overview of Realtime Process Scheduling
The SCHED_RR Policy
The SCHED_FIFO Policy
The SCHED_BATCH and SCHED_IDLE Policies
Realtime Process Scheduling API
Realtime Priority Ranges
Modifying and Retrieving Policies and Priorities
Relinquishing the CPU
The SCHED_RR Time Slice
CPU Affinity
Summary
Exercises
36. Process Resources
Process Resource Usage
Process Resource Limits
Details of Specific Resource Limits
Summary
Exercises
37. Daemons
Overview
Creating a Daemon
Guidelines for Writing Daemons
Using SIGHUP to Reinitialize a Daemon
Logging Messages and Errors Using syslog
Summary
Exercise
38. Writing Secure Privileged Programs
Is a Set-User-ID or SetGroup-ID Program Required?
Operate with Least Privilege
Be Careful When Executing a Program
Avoid Exposing Sensitive Information
Confine the Process
Beware of Signals and Race Conditions
Pitfalls When Performing File Operations and File I/O
Don't Trust Inputs or the Environment
Beware of Buffer Overruns
Beware of Denial-of-Service Attacks
Check Return Statuses and Fail Safely
Summary
Exercises
39. Capabilities
Rationale for Capabilities
The Linux Capabilities
Process and File Capabilities
Process Capabilities
File Capabilities
Purpose of the Process Permitted and Effective Capability Sets
Purpose of the File Permitted and Effective Capability Sets
Purpose of the Process and File Inheritable Sets
Assigning and Viewing File Capabilities from the Shell
The Modern Capabilities Implementation
Transformation of Process Capabilities During exec()
Capability Bounding Set
Preserving root Semantics
Effect on Process Capabilities of Changing User IDs
Changing Process Capabilities Programmatically
Creating Capabilities-Only Environments
Discovering the Capabilities Required by a Program
Older Kernels and Systems Without File Capabilities
Summary
Exercise
40. Login Accounting
Overview of the utmp and wtmp Files
The utmpx API
The utmpx Structure
Retrieving Information from the utmp and wtmp Files
Retrieving the Login Name: getlogin()
Updating the utmp and wtmp Files for a Login Session
The lastlog File
Summary
Exercises
41. Fundamentals of Shared Libraries
Object Libraries
Static Libraries
Overview of Shared Libraries
Creating and Using Shared Libraries—A First Pass
Creating a Shared Library
Position-Independent Code
Using a Shared Library
The Shared Library Soname
Useful Tools for Working with Shared Libraries
Shared Library Versions and Naming Conventions
Installing Shared Libraries
Compatible Versus Incompatible Libraries
Upgrading Shared Libraries
