C Programming in the Linux Environment

Subtitle: An Introduction

Introduction

Briefly introduce the topic.

Mention the division of the programming world into Windows and Linux camps.

Highlight the popularity and community around Linux.

What is Linux?

Explain Linux as a clone of the UNIX operating system.

Mention Linus Torvalds and the open-source nature of Linux.

Discuss the availability and flexibility of Linux.

Linux Distributions

Introduce popular Linux distributions like Ubuntu, RedHat, SUSE, and more.

Highlight that these distributions contain the Linux kernel and various application programs.

C Programming Under Linux

Explain that C programming in Linux is similar but also different from other platforms.

Mention that the usage of standard library functions remains consistent.

"Hello Linux" Program

Present a simple "Hello World" C program for Linux.

Explain how to compile and execute the program using NetBeans or GCC.

Introduction to Processes

Explain the concept of processes in Linux.

Highlight that Linux can run multiple processes simultaneously.

The "Hello Linux" Program - getpid()

Introduce the getpid() function.

Show how getpid() is used to retrieve the process ID of a running program.

Parent and Child Processes

Describe the parent-child relationship between processes.

Introduce the fork() function and show a sample program illustrating it.

Child Process Output

Show the output of the program demonstrating fork() and explain why it appears as it does.

A Real-World Example - Copying Files

Explain the need for creating child processes.

Describe a hypothetical scenario where child processes are useful for concurrent tasks.

"Child and Parent Process IDs" Program

Present a program showing how to retrieve both child and parent process IDs.

Explain the use of getpid() and getppid().

Process Tree in Linux

Describe the hierarchical structure of processes in Linux.

Mention the "init" process as the root of the process tree.

Executing Programs in Child Processes

Introduce the exec() family of functions.

Show how to execute a new program in a child process using execl().

Exec Function Parameters

Explain the parameters required by the exec() functions.

Highlight the importance of using NULL as the end-of-arguments marker.

Code Execution with exec()

Describe how the code execution changes after calling an exec() function.

Use an example with ls to illustrate the point.

Combining fork() and exec()

Emphasize the typical use of fork() and exec() together to create child processes.

Linux Programming Essentials

Subtitle: Zombies, Orphans, and Event-Driven Programming

Introduction to Process Table

Linux maintains a 'Process Table' that contains information about running processes.

This table includes an 'exit code' indicating the reason for termination.

Parent processes query the exit code to remove entries in the table.

Child Terminates Earlier

When a child process ends before the parent, its entry remains in the process table.

Such processes are known as 'Zombies.'

A parent should query immediately to prevent a Zombie.

Parent Terminates Earlier

If the parent terminates without querying, the child becomes an 'Orphan.'

The 'init' process adopts the Orphaned process, then queries the table.

The child process does not become a Zombie.

Handling Child and Parent Termination

Prevent Zombie and Orphan processes by querying exit codes in the parent.

Cleanup is important for ensuring proper resource management.

Code Example: Preventing Zombies

Show the C code example with fork, waitpid, and signal handling.

Signal Communication

Communication with the OS is done using signals.

Signals are sent from the OS to the program.

Signals can be caught and handled by the program.

Handling SIGINT and SIGTERM

SIGINT (Ctrl+C) and SIGTERM (kill command) can be handled in C programs.

By registering signal handlers, programs can define custom behavior for these signals.

Handling Multiple Signals

Multiple signals can be handled using different signal handlers.

Register each signal with its associated handler using g_signal_connect.

Signal Blocking

Signal blocking is used to defer signal delivery during critical code sections.

Use sigprocmask to block and unblock signals.

Blocked signals are delivered once unblocked.

Event-Driven Programming in Linux

Event-driven programming is used for creating GUI programs.

GTK library simplifies the creation of GUI applications.

Events trigger specific functions within the program.

Creating a Simple Window with GTK

Show a C code example for creating a basic window using GTK.

Explain the steps: initialization, creating a window, setting title, and handling destroy signal.

Drawing Shapes in a GTK Window

Show another C code example for drawing shapes in a GTK window.

Explain how to handle the expose_event signal and use the Gdk drawing functions.

Conclusion

You've explored Linux programming essentials.

Signal handling, event-driven programming, and GTK usage are powerful tools.

Now, you're ready to dive deeper into Linux development.

Questions and Answers

Open the Questions for questions and Answers.