Sri Manikanta Palakollu

Practical System Programming with C

Pragmatic Example Applications in Linux and Unix-Based Operating Systems

1st ed.
Sri Manikanta Palakollu
freelance, Hanuman Junction, Hanuman Junction, 521105, Andhra Pradesh, India
ISBN 978-1-4842-6320-4e-ISBN 978-1-4842-6321-1
https://doi.org/10.1007/978-1-4842-6321-1
© Sri Manikanta Palakollu 2021
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Introduction
The main goal of this book is to introduce system programming using the C language. The topics covered in this book teach you how to programmatically manipulate Linux and POSIX-based operating systems. The wide variety of topics include

  • The basics of the Linux operating system

  • Multithreaded programming in C

  • Deadlocks

  • An introduction to POSIX standards

  • The need for processes and signals

  • Various IPC techniques

  • Developing client-server architecture using TCP and UDP protocols

The prerequisites for learning the concepts discussed in this book are

  • A basic knowledge of the C programming language

  • A basic knowledge of operating systems

Acknowledgments

I would like to thank my savior, the Lord Jesus Christ, for giving me the strength, knowledge, wisdom, and ability to write this book. I would like to express my deepest gratitude to the Apress team: Steve Anglin (Acquisition Editor), Mark Powers (Coordinating Editor), and Matthew Moodie (Development Editor) for giving me this opportunity and providing constant support during the entire development process. Thanks to my technical reviewer for his efforts in reviewing this book.

Special thanks to my friends Sai Vardhan Poloju, Aravind Medamoni, Vamsi Thanjagari, and PTS Vaishnavi for helping me during this journey.

Thanks to my spiritual parents, Rev. Amos Varma and Amrutha, for their constant prayer support and love. I would like to thank my parents, Basaveswara Rao and Vijaya Lakshmi, for their love and support. I thank my brother Santhosh and my sister Sri Lakshmi for helping me design the diagrams in this book.

—Sri Manikanta Palakollu

Table of Contents
Chapter 1:​ Introduction to the Linux Environment 1
Getting Familiar with the Linux Architecture 2
Hardware Layer 3
Kernel 3
Shell 8
System Library 8
Linux Kernels vs.​ Other OS Kernels 9
Introduction to Files 9
Text File 10
Program File 10
Binary File 10
Special File 11
Regular File 11
File Handling Utilities 11
mkdir 11
cd 12
rmdir 12
rm 13
touch 15
ls 15
cat 17
head 17
tail 19
nl 20
wc 21
copy 22
ulimit 22
File Permission Commands 22
chmod 23
Process Utilities 26
Process 26
Process Commands 27
Network Utilities 29
ifconfig 30
hostname 30
netstat 30
nslookup 32
traceroute 33
host 34
ping 34
dig 35
Summary 36
Chapter 2:​ Multithreading in C 37
Introduction to Threads 37
Thread Classification 39
User-Level Threads 39
Kernel-Level Threads 41
Threads vs.​ Processes 42
New State 43
Ready State 44
Wait State 44
Running State 44
Terminated 44
Introduction to Multithreading 45
Multitasking Architecture 45
Multithreading Architecture 46
Importance of Multithreading 47
Concurrency 49
Parallelism 50
Support of Multithreading in C 50
pthread_​create 51
pthread_​join 52
pthread_​self 53
pthread_​equal 53
pthread_​exit 53
pthread_​cancel 54
pthread_​detach 54
Creating Threads 54
Practical Examples of Multithreading 58
Thread Termination 58
Thread Equal Property 59
Passing a Single Argument to a Thread Function 60
Passing Multiple Arguments as Parameters 61
The Relationship Between Threads and the CPU 63
Multithreading Use Cases 63
Summary 64
Chapter 3:​ Introduction to POSIX Standards and System-Level APIs 65
Understanding POSIX Standards 65
POSIX.​1 Standards 66
POSIX.​1b Standards 67
POSIX.​1c Standards 67
POSIX.​2 Standards 67
POSIX Support 68
Introduction to APIs 68
User Mode 69
Supervisor Mode 69
The Importance of System-Level APIs 70
Built-in APIs in C 70
Summary 71
Chapter 4:​ Files and Directories 73
File Systems 73
File Metadata and Inodes 78
System Calls and I/​O Operations for Files 82
creat 85
open 87
close 88
read 89
write 91
Append Operations in Files Using System Calls 92
File Permissions 93
chmod Function to Change Permissions 93
File Permissions Check 94
Soft and Hard Links 96
Soft Links 96
Hard Links 101
System Calls for Directories 104
Creating a Directory 104
Deleting a Directory 105
Getting the Current Working Directory 106
Changing Directory 107
Reading a Directory 108
Closing a Directory 109
Summary 111
Chapter 5:​ Process and Signals 113
Introduction to the Process Environment 114
Environment List 115
Memory Layout of a C Program 117
Command-Line Arguments 118
Process Termination Methodologies 119
Environment Variables 121
User-Level Environment Variables 121
System-Level Environment Variable 121
Environment Variable Examples 121
Accessing an Environment Variable 122
Setting a New Environment Variable 122
Deleting Environment Variables 123
Accessing Environment Variables in C 123
Setting a New Environment Variable Using C 124
Deleting an Environment Variable 126
Kernel Support for Processes 127
Process Scheduler 128
Memory Manager 128
Virtual File System 129
Process Creation 129
Zombie Process 132
Orphan Process 133
System Calls for Process Management 134
Introduction to Signals 152
Catch the Signal 152
Ignore the Signal 152
Default Action 153
Types of Signals 156
System Calls for Signals 157
Summary 163
Chapter 6:​ Interprocess Communication 165
Introduction to IPC 166
Independent Processes 166
Cooperating Processes 166
The Benefits of IPC 168
Modes of Communication 168
Simplex 169
Half Duplex 169
Full Duplex 170
Types of IPC 171
Pipes 172
FIFO (Named Pipe) 173
Message Queues 173
Semaphores 173
Shared Memory 174
Sockets 174
Anonymous Pipes 174
APIs for Anonymous Pipes 175
Creating Anonymous Pipes 177
Implementation of Pipes Using Child and Parent Processes 180
Working with Named Pipes 183
mknod() System Call 183
mkfifo() System Call 185
mknod vs.​ mkfifo 186
Creating FIFO 186
Using Message Queues 192
APIs for Message Queues 193
Message Queue Implementation 201
Introduction to Semaphores 206
Binary Semaphores 206
Counting Semaphores 207
Characteristics of Semaphores 207
The Advantages of Using a Semaphore 207
The Disadvantages of Using a Semaphore 208
Semaphore vs.​ Mutex 208
APIs for a Semaphore 209
Accessing Global Data Without Semaphores 211
Implementing the Data Consistent Model Using a Semaphore and a Mutex 212
Summary 214
Chapter 7:​ Shared Memory 215
Introduction to Shared Memory 215
API for Shared Memory 218
shmget() 218
shmat() 219
shmdt() 220
shmctl() 220
Kernel Support for Shared Memory 221
Implementation of Shared Memory 222
Shared Memory Writers Program 222
Shared Memory Reader Program 223
Summary 224
Chapter 8:​ Socket Programming 225
Introduction to Sockets 225
Stream Sockets 226
Datagram Sockets 226
Raw Sockets 226
Domain Sockets 227
Internet Domain Sockets 227
IPC Over Network 227
Communication Style 227
Namespaces 228
Protocol 228
API for Socket Programming 228
OSI Architecture Model 230
Physical Layer 231
Data Link Layer 232
Network Layer 233
Transport Layer 234
Session Layer 235
Presentation Layer 236
Application Layer 236
Advantages of the OSI Model 237
Disadvantages of the OSI Model 237
TCP/​IP Architecture Model 237
Network Access Layer 239
Internet Layer 239
Transport Layer 240
Application Layer 241
Advantages of TCP/​IP 242
Disadvantages of TCP/​IP 242
Client-Server Architecture 242
Client 242
Server 243
Examining the Client-Server Architecture 243
Advantages of the Client-Server Model 244
Disadvantages of the Client-Server Model 244
System Calls for Socket Programming 244
socket() 245
bind() 246
listen() 246
accept() 247
send() 247
recv() 248
sendto() 249
recvfrom() 249
close() 250
Implementation of Client Server Architecture 250
TCP Client-Server Architecture 250
TCP Client-Server Code 253
UDP Client Server Architecture 259
UDP Client-Server Code 260
Summary 266
Index 267
About the Author
Sri Manikanta Palakollu

is a programmer and software developer with experience in C, C++, Java, and Python as well as Linux and POSIX-based systems-level programming. He is a tech reviewer for various tech book publishers. He has written many technical articles on data science, programming, and cybersecurity. Sri Manikanta has won a national-level hackathon and contributes to various open source projects.

 
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