Linux System Programming by Love, Robert -- Read -- Imperial Library of Trantor

Index

Linux System Programming Foreword Preface

Audience and Assumptions Contents of This Book Versions Covered in This Book Conventions Used in This Book Safari® Books Online Using Code Examples How to Contact Us Acknowledgments

1. Introduction and Essential Concepts

System Programming

System Calls

Invoking system calls

The C Library The C Compiler

APIs and ABIs

APIs ABIs

Standards

POSIX and SUS History C Language Standards Linux and the Standards This Book and the Standards

Concepts of Linux Programming

Files and the Filesystem

Regular files Directories and links Hard links Symbolic links Special files Filesystems and namespaces

Processes

Threads Process hierarchy

Users and Groups Permissions Signals Interprocess Communication Headers Error Handling

Getting Started with System Programming

2. File I/O

Opening Files

The open( ) System Call

Flags for open( )

Owners of New Files Permissions of New Files The creat( ) Function Return Values and Error Codes

Reading via read( )

Return Values Reading All the Bytes Nonblocking Reads Other Error Values Size Limits on read( )

Writing with write( )

Partial Writes Append Mode Nonblocking Writes Other Error Codes Size Limits on write( ) Behavior of write( )

Synchronized I/O

fsync( ) and fdatasync( )

Return values and error codes

sync( ) The O_SYNC Flag O_DSYNC and O_RSYNC

Direct I/O Closing Files

Error Values

Seeking with lseek( )

Seeking Past the End of a File Error Values Limitations

Positional Reads and Writes

Error Values

Truncating Files Multiplexed I/O

select( )

Return values and error codes select( ) example Portable sleeping with select( ) pselect( )

poll( )

Return values and error codes poll( ) example ppoll( )

poll( ) Versus select( )

Kernel Internals

The Virtual Filesystem The Page Cache Page Writeback

Conclusion

3. Buffered I/O

User-Buffered I/O

Block Size

Standard I/O

File Pointers

Opening Files

Modes

Opening a Stream via File Descriptor Closing Streams

Closing All Streams

Reading from a Stream

Reading a Character at a Time

Putting the character back

Reading an Entire Line

Reading arbitrary strings

Reading Binary Data

Writing to a Stream

Writing a Single Character Writing a String of Characters Writing Binary Data

Sample Program Using Buffered I/O Seeking a Stream

Obtaining the Current Stream Position

Flushing a Stream Errors and End-of-File Obtaining the Associated File Descriptor Controlling the Buffering Thread Safety

Manual File Locking Unlocked Stream Operations

Critiques of Standard I/O Conclusion

4. Advanced File I/O

Scatter/Gather I/O

readv( ) and writev( )

Return values writev( ) example readv( ) example Implementation

The Event Poll Interface

Creating a New Epoll Instance Controlling Epoll Waiting for Events with Epoll Edge- Versus Level-Triggered Events

Mapping Files into Memory

mmap( )

The page size

sysconf( ) getpagesize( ) PAGE_SIZE

Return values and error codes Associated signals

munmap( ) Mapping Example Advantages of mmap( ) Disadvantages of mmap( ) Resizing a Mapping

Return values and error codes

Changing the Protection of a Mapping

Return values and error codes

Synchronizing a File with a Mapping

Return values and error codes

Giving Advice on a Mapping

Return values and error codes

Advice for Normal File I/O

The posix_fadvise( ) System Call

Return values and error codes

The readahead( ) System Call

Return values and error codes

Advice Is Cheap

Synchronized, Synchronous, and Asynchronous Operations

Asynchronous I/O

Thread-based asynchronous I/O

I/O Schedulers and I/O Performance

Disk Addressing The Life of an I/O Scheduler Helping Out Reads

The Deadline I/O Scheduler The Anticipatory I/O Scheduler The CFQ I/O Scheduler The Noop I/O Scheduler

Selecting and Configuring Your I/O Scheduler Optimizing I/O Performance

Scheduling I/O in user space

Sorting by path Sorting by inode Sorting by physical block

Conclusion

5. Process Management

The Process ID

Process ID Allocation The Process Hierarchy pid_t Obtaining the Process ID and Parent Process ID

Running a New Process

The Exec Family of Calls

The rest of the family Error values

The fork( ) System Call

Copy-on-write vfork( )

Terminating a Process

Other Ways to Terminate atexit( ) on_exit( ) SIGCHLD

Waiting for Terminated Child Processes

Waiting for a Specific Process Even More Waiting Versatility BSD Wants to Play: wait3( ) and wait4( ) Launching and Waiting for a New Process Zombies

Users and Groups

Real, Effective, and Saved User and Group IDs Changing the Real or Saved User or Group ID Changing the Effective User or Group ID Changing the User and Group IDs, BSD Style Changing the User and Group IDs, HP-UX Style Preferred User/Group ID Manipulations Support for Saved User IDs Obtaining the User and Group IDs

Sessions and Process Groups

Session System Calls Process Group System Calls Obsolete Process Group Functions

Daemons Conclusion

6. Advanced Process Management

Process Scheduling

Big-Oh Notation Timeslices I/O- Versus Processor-Bound Processes Preemptive Scheduling Threading

Yielding the Processor

Legitimate Uses Yielding, Past and Present

Process Priorities

nice( ) getpriority( ) and setpriority( ) I/O Priorities

Processor Affinity

sched_getaffinity() and sched_setaffinity( )

Real-Time Systems

Hard Versus Soft Real-Time Systems Latency, Jitter, and Deadlines Linux's Real-Time Support Linux Scheduling Policies and Priorities

The first in, first out policy The round-robin policy The normal policy The batch scheduling policy Setting the Linux scheduling policy

Error codes

Setting Scheduling Parameters

Error codes Determining the range of valid priorities

sched_rr_get_interval( )

Error codes

Precautions with Real-Time Processes Determinism

Prefaulting data and locking memory CPU affinity and real-time processes

Resource Limits

The Limits

Default limits

Setting and Retrieving Limits

Error codes

7. File and Directory Management

Files and Their Metadata

The Stat Family Permissions Ownership Extended Attributes

Keys and values Extended attribute namespaces Extended attribute operations

Retrieving an extended attribute Setting an extended attribute Listing the extended attributes on a file Removing an extended attribute

Directories

The Current Working Directory

Obtaining the current working directory Changing the current working directory

Creating Directories Removing Directories Reading a Directory's Contents

Reading from a directory stream Closing the directory stream System calls for reading directory contents

Links

Hard Links Symbolic Links Unlinking

Copying and Moving Files

Copying Moving

Device Nodes

Special Device Nodes The Random Number Generator

Out-of-Band Communication Monitoring File Events

Initializing inotify Watches

Adding a new watch Watch masks

inotify Events

Reading inotify events

Advanced inotify events

Linking together move events

Advanced Watch Options Removing an inotify Watch Obtaining the Size of the Event Queue Destroying an inotify Instance

8. Memory Management

The Process Address Space

Pages and Paging

Sharing and copy-on-write

Memory Regions

Allocating Dynamic Memory

Allocating Arrays Resizing Allocations Freeing Dynamic Memory Alignment

Allocating aligned memory

Older interfaces

Other alignment concerns

Nonstandard types Playing with pointers

Managing the Data Segment Anonymous Memory Mappings

Creating Anonymous Memory Mappings Mapping /dev/zero

Advanced Memory Allocation

Fine-Tuning with malloc_usable_size( ) and malloc_trim( )

Debugging Memory Allocations

Obtaining Statistics

Stack-Based Allocations

Duplicating Strings on the Stack Variable-Length Arrays

Choosing a Memory Allocation Mechanism Manipulating Memory

Setting Bytes Comparing Bytes Moving Bytes Searching Bytes Frobnicating Bytes

Locking Memory

Locking Part of an Address Space Locking All of an Address Space Unlocking Memory Locking Limits Is a Page in Physical Memory?

Opportunistic Allocation

Overcommitting and OOM

9. Signals

Signal Concepts

Signal Identifiers Signals Supported by Linux

Basic Signal Management

Waiting for a Signal, Any Signal Examples Execution and Inheritance Mapping Signal Numbers to Strings

Sending a Signal

Permissions Examples Sending a Signal to Yourself Sending a Signal to an Entire Process Group

Reentrancy

Guaranteed-Reentrant Functions

Signal Sets

More Signal Set Functions

Blocking Signals

Retrieving Pending Signals Waiting for a Set of Signals

Advanced Signal Management

The siginfo_t Structure The Wonderful World of si_code

Sending a Signal with a Payload

Example

Conclusion

10. Time

Time's Data Structures

The Original Representation And Now, Microsecond Precision Even Better: Nanosecond Precision Breaking Down Time A Type for Process Time

POSIX Clocks

Time Source Resolution

Getting the Current Time of Day

A Better Interface An Advanced Interface Getting the Process Time

Setting the Current Time of Day

Setting Time with Precision An Advanced Interface for Setting the Time

Playing with Time Tuning the System Clock Sleeping and Waiting

Sleeping with Microsecond Precision Sleeping with Nanosecond Resolution An Advanced Approach to Sleep A Portable Way to Sleep Overruns Alternatives to Sleeping

Timers

Simple Alarms Interval Timers Advanced Timers

Creating a timer Arming a timer Obtaining the expiration of a timer Obtaining the overrun of a timer Deleting a timer

A. GCC Extensions to the C Language

GNU C Inline Functions Suppressing Inlining Pure Functions Constant Functions Functions That Do Not Return Functions That Allocate Memory Forcing Callers to Check the Return Value Marking Functions As Deprecated Marking Functions As Used Marking Functions or Parameters As Unused Packing a Structure Increasing the Alignment of a Variable Placing Global Variables in a Register Branch Annotation Getting the Type of an Expression Getting the Alignment of a Type The Offset of a Member Within a Structure Obtaining the Return Address of a Function Case Ranges Void and Function Pointer Arithmetic More Portable and More Beautiful in One Fell Swoop

Bibliography

Books on the C Programming Language Books on Linux Programming

About the Author Colophon Copyright

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