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Linux System Programming Techniques

Linux System Programming Techniques

By : Jack-Benny Persson
4.8 (8)
Buy this Book
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Linux System Programming Techniques

Linux System Programming Techniques

4.8 (8)
By: Jack-Benny Persson
Buy this Book

Overview of this book

Linux is the world's most popular open source operating system (OS). Linux System Programming Techniques will enable you to extend the Linux OS with your own system programs and communicate with other programs on the system. The book begins by exploring the Linux filesystem, its basic commands, built-in manual pages, the GNU compiler collection (GCC), and Linux system calls. You'll then discover how to handle errors in your programs and will learn to catch errors and print relevant information about them. The book takes you through multiple recipes on how to read and write files on the system, using both streams and file descriptors. As you advance, you'll delve into forking, creating zombie processes, and daemons, along with recipes on how to handle daemons using systemd. After this, you'll find out how to create shared libraries and start exploring different types of interprocess communication (IPC). In the later chapters, recipes on how to write programs using POSIX threads and how to debug your programs using the GNU debugger (GDB) and Valgrind will also be covered. By the end of this Linux book, you will be able to develop your own system programs for Linux, including daemons, tools, clients, and filters.
Table of Contents (14 chapters)
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Preface
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Preface
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Who this book is for
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What this book covers
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To get the most out of this book
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Code in Action
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Download the color images
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Conventions used
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Sections
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Get in touch
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Reviews
1
Chapter 1: Getting the Necessary Tools and Writing Our First Linux Programs
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Chapter 1: Getting the Necessary Tools and Writing Our First Linux Programs
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Technical requirements
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Installing GCC and GNU Make
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Installing GDB and Valgrind
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Writing a simple C program for Linux
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Writing a program that parses command-line options
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Looking up information in the built-in manual page
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Searching the manual for information
Lock Free Chapter
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Chapter 2: Making Your Programs Easy to Script
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Chapter 2: Making Your Programs Easy to Script
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Technical requirements
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Return values and how to read them
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Exiting a program with a relevant return value
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Redirecting stdin, stdout, and stderr
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Connecting programs using pipes
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Writing to stdout and stderr
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Reading from stdin
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Writing a pipe-friendly program
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Redirecting the result to a file
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Reading environment variables
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Chapter 3: Diving Deep into C in Linux
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Chapter 3: Diving Deep into C in Linux
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Technical requirements
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Linking against libraries using GCC
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Changing C standards
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Using system calls – and when not to use them
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Getting information about Linux- and Unix-specific header files
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Defining feature test macros
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Looking at the four stages of compilation
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Compiling with Make
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Writing a generic Makefile with GCC options
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Writing a simple Makefile
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Writing a more advanced Makefile
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Chapter 4: Handling Errors in Your Programs
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Chapter 4: Handling Errors in Your Programs
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Technical requirements
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Why error handling is important in system programming
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Handling some common errors
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Error handling and errno
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Handling more errno macros
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Using errno with strerror()
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Using errno with perror()
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Returning an error value
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Chapter 5: Working with File I/O and Filesystem Operations
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Chapter 5: Working with File I/O and Filesystem Operations
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Technical requirements
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Reading inode information and learning the filesystem
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Creating soft links and hard links
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Creating files and updating the timestamp
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Deleting files
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Getting access rights and ownership
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Setting access rights and ownership
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Writing to files with file descriptors
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Reading from files with file descriptors
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Writing to files with streams
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Reading from files with streams
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Reading and writing binary data with streams
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Moving around inside a file with lseek()
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Moving around inside a file with fseek()
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Chapter 6: Spawning Processes and Using Job Control
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Chapter 6: Spawning Processes and Using Job Control
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Technical requirements
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Exploring how processes are created
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Using job control in Bash
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Controlling and terminating processes using signals
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Replacing the program in a process with execl()
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Forking a process
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Executing a new program in a forked process
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Starting a new process with system()
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Creating a zombie process
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Learning about what orphans are
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Creating a daemon
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Implementing a signal handler
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Chapter 7: Using systemd to Handle Your Daemons
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Chapter 7: Using systemd to Handle Your Daemons
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Technical requirements
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Getting to know systemd
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Writing a unit file for a daemon
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Enabling and disabling a service – and starting and stopping it
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Creating a more modern daemon for systemd
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Making the new daemon a systemd service
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Reading the journal
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Chapter 8: Creating Shared Libraries
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Chapter 8: Creating Shared Libraries
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Technical requirements
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The what and why of libraries
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Creating a static library
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Using a static library
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Creating a dynamic library
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Installing the dynamic library on the system
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Using the dynamic library in a program
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Compiling a statically linked program
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Chapter 9: Terminal I/O and Changing Terminal Behavior
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Chapter 9: Terminal I/O and Changing Terminal Behavior
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Technical requirements
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Viewing terminal information
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Changing terminal settings with stty
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Investigating TTYs and PTYs and writing to them
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Checking if it's a TTY
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Creating a PTY
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Disabling echo for password prompts
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Reading the terminal size
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Chapter 10: Using Different Kinds of IPC
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Chapter 10: Using Different Kinds of IPC
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Technical requirements
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Using signals for IPC – building a client for the daemon
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Communicating with a pipe
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FIFO – using it in the shell
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FIFO – building the sender
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FIFO – building the receiver
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Message queues – creating the sender
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Message queues – creating the receiver
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Communicating between child and parent with shared memory
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Using shared memory between unrelated processes
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Unix socket – creating the server
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Unix socket – creating the client
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Chapter 11: Using Threads in Your Programs
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Chapter 11: Using Threads in Your Programs
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Technical requirements
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Writing your first threaded program
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Reading return values from threads
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Causing a race condition
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Avoiding race conditions with mutexes
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Making the mutex program more efficient
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Using condition variables
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Chapter 12: Debugging Your Programs
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Chapter 12: Debugging Your Programs
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Technical requirements
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Starting GDB
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Stepping inside a function with GDB
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Investigating memory with GDB
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Modifying variables during runtime
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Using GDB on a program that forks
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Debugging programs with multiple threads
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Finding a simple memory leak with Valgrind
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Finding buffer overflows with Valgrind
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Why subscribe?
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Other Books You May Enjoy
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Other Books You May Enjoy
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Making the new daemon a systemd service

Now that we've made a new-style daemon in the previous recipe, we'll see that it's even easier to make a unit file for this daemon.

Knowing how to write unit files to new-style daemons is important since more and more daemons are written this way. When making new daemons for Linux, we should make them in this new style.

Getting ready

For this recipe, you'll need to complete the previous one. It's the daemon from that recipe that we'll use here.

How to do it...

Here, we will make the new-style daemon a systemd service:

  1. Let's begin by moving the daemon to /usr/local/sbin, just as we did with the traditional daemon. Remember, you'll need to be root for this:
    $> sudo mv new-style-daemon /usr/local/sbin/
  2. Now we'll write the new unit file. Create the /etc/systemd/system/new-style-daemon.service file and give it the following content. Remember, you'll need to be root to create...
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