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[PDF] POSIX Threads Essentials: A Hands-on Tutorial


Introduction




In computing, POSIX Threads, commonly known as pthreads, is an execution model that exists independently from a programming language, as well as a parallel execution model. It allows a program to control multiple different flows of work that overlap in time. Each flow of work is referred to as a thread, and creation and control over these flows is achieved by making calls to the POSIX Threads API.




[PDF] Programming with POSIX threads download



POSIX Threads is an API defined by the Institute of Electrical and Electronics Engineers (IEEE) standard POSIX.1c, Threads extensions (IEEE Std 1003.1c-1995). Implementations of the API are available on many Unix-like POSIX-conformant operating systems such as FreeBSD, NetBSD, OpenBSD, Linux, macOS, Android, Solaris, Redox, and AUTOSAR Adaptive, typically bundled as a library libpthread. DR-DOS and Microsoft Windows implementations also exist: within the SFU/SUA subsystem which provides a native implementation of a number of POSIX APIs, and also within third-party packages such as pthreads-w32, which implements pthreads on top of existing Windows API.


POSIX Threads can provide significant benefits for parallel programming such as improving performance, scalability, modularity, portability, and simplicity. However, using POSIX Threads also requires some skills and knowledge such as understanding concurrency issues, synchronizing threads, managing memory allocation, debugging errors, etc. Therefore, learning how to program with POSIX Threads can be challenging but rewarding for programmers who want to take advantage of parallel computing.


In this article, we will show you how to download and install POSIX Threads on different operating systems, how to use POSIX Threads in C/C++ programming, and how to download a PDF book on programming with POSIX Threads. By the end of this article, you should have a basic understanding of what POSIX Threads are and how to use them effectively.


How to download and install POSIX Threads




Downloading POSIX Threads for different operating systems




Depending on your operating system, you may already have POSIX Threads installed or you may need to download and install them separately. Here are some links and instructions for downloading POSIX Threads for Linux, Windows, macOS, and Android:


  • Linux: Most Linux distributions come with POSIX Threads pre-installed as part of the GNU C Library (glibc). However, if you need to update or install POSIX Threads manually, you can use the package manager of your distribution (such as apt, yum, pacman, etc.) or download the source code from https://www.gnu.org/software/libc/ and compile it yourself.





  • macOS: macOS comes with POSIX Threads pre-installed as part of the Darwin kernel. However, if you need to update or install POSIX Threads manually, you can use the Xcode command-line tools or Homebrew. You can download Xcode from https://developer.apple.com/xcode/ and install the command-line tools by running xcode-select --install in a terminal. You can download Homebrew from https://brew.sh/ and install POSIX Threads by running brew install glibc in a terminal.





Installing POSIX Threads on Linux




If you are using Linux, you probably already have POSIX Threads installed as part of the GNU C Library (glibc). However, if you need to update or install POSIX Threads manually, you can use the package manager of your distribution or compile from source. Here are some examples of how to do that:


  • If you are using Debian or Ubuntu, you can use apt to install glibc by running sudo apt-get update and then sudo apt-get install libc6-dev in a terminal.



  • If you are using Fedora or CentOS, you can use yum to install glibc by running sudo yum update and then sudo yum install glibc-devel in a terminal.



  • If you are using Arch Linux or Manjaro, you can use pacman to install glibc by running sudo pacman -Syu and then sudo pacman -S glibc in a terminal.



Installing POSIX Threads on Windows




If you are using Windows, you have two options for installing POSIX Threads: using the SFU/SUA subsystem or using third-party packages. Here are some steps for doing that:




  • If you want to use third-party packages, you can download pthreads-w32 from https://sourceware.org/pthreads-win32/. Then, you need to extract the files to a folder of your choice. After that, you need to add the folder to your PATH environment variable and copy the libpthreadGC2.a file to your compiler's library folder. Then, you can include the pthread.h header file and link with the libpthread library in your C/C++ code.



Installing POSIX Threads on macOS




If you are using macOS, you already have POSIX Threads installed as part of the Darwin kernel. However, if you need to update or install POSIX Threads manually, you can use the Xcode command-line tools or Homebrew. Here are some examples of how to do that:


  • If you want to use the Xcode command-line tools, you need to download Xcode from https://developer.apple.com/xcode/ and install it on your Mac. Then, you need to install the command-line tools by running xcode-select --install in a terminal. After that, you can use the POSIX Threads API as if you were on a Unix-like system.



  • If you want to use Homebrew, you need to download Homebrew from https://brew.sh/ and install it on your Mac. Then, you need to install glibc by running brew install glibc in a terminal. After that, you can use the POSIX Threads API as if you were on a Unix-like system.



Installing POSIX Threads on Android




If you are using Android, you can use POSIX Threads as part of the Android Native Development Kit (NDK) or the Java Native Interface (JNI). Here are some steps for doing that:


  • If you want to use the NDK, you need to download it from https://developer.android.com/ndk/downloads and install it on your computer. Then, you need to create a project that uses native code and add the pthread.h header file and link with the libpthread library in your C/C++ code. After that, you can build and run your project on your Android device.



  • If you want to use the JNI, you need to create a project that uses Java code and native code. Then, you need to write a Java class that declares native methods and load a native library that implements those methods using System.loadLibrary(). In your native code, you need to include the pthread.h header file and link with the libpthread library. After that, you can call the native methods from your Java code and run your project on your Android device.



How to use POSIX Threads in C/C++ programming




Including the pthread.h header file




To use POSIX Threads in C/C++ programming, you need to include the pthread.h header file at the beginning of your source code. This header file defines all the types, functions, and constants related to POSIX Threads. For example:


#include


#include


#include


// Your code goes here


You also need to link with the libpthread library when compiling your code. This library provides the implementation of the POSIX Threads API. Depending on your compiler and operating system, you may need to use different options to link with the library. For example:


gcc -o myprogram myprogram.c -lpthread // For GCC on Linux or macOS cl /Fe:myprogram.exe myprogram.c /link pthreadVC2.lib // For Visual Studio on Windows


Creating and joining threads




To create a new thread, you need to use the pthread_create function. This function takes four arguments: a pointer to a pthread_t variable that will store the thread identifier, a pointer to a pthread_attr_t structure that specifies the thread attributes (such as stack size, scheduling policy, etc.), a pointer to a function that will be executed by the thread, and a pointer to an argument that will be passed to the function. For example:


// Define a function that will be executed by the thread void *say_hello(void *arg) char *name = (char *) arg; // Cast the argument to a char pointer printf("Hello, %s!\n", name); // Print a message return NULL; // Return NULL as the thread exit status // Create a new thread pthread_t thread; // Declare a pthread_t variable pthread_attr_t attr; // Declare a pthread_attr_t variable pthread_attr_init(&attr); // Initialize the thread attributes with default values char *name = "Alice"; // Define an argument for the thread function int rc = pthread_create(&thread, &attr, say_hello, name); // Create the thread if (rc != 0) // Check for errors perror("pthread_create"); // Print an error message exit(EXIT_FAILURE); // Exit with failure status


To join a thread, you need to use the pthread_join function. This function takes two arguments: the thread identifier of the thread to join, and a pointer to a void pointer that will store the thread exit status. The function blocks until the thread terminates and returns 0 on success or an error code on failure. For example:


// Join the thread void *status; // Declare a void pointer for the thread exit status int rc = pthread_join(thread, &status); // Join the thread if (rc != 0) // Check for errors perror("pthread_join"); // Print an error message exit(EXIT_FAILURE); // Exit with failure status printf("Thread exited with status %p\n", status); // Print the thread exit status


Passing arguments and returning values from threads




To pass arguments and return values from threads, you need to use void pointers and casting. A void pointer is a pointer that can point to any type of data, but it cannot be dereferenced directly. To use a void pointer, you need to cast it to the appropriate type before dereferencing it. For example:


// Define a function that takes an int argument and returns an int value void *square(void *arg) int n = *(int *) arg; // Cast the argument to an int pointer and dereference it int result = n * n; // Compute the square of n return (void *) result; // Cast the result to a void pointer and return it // Create a new thread and pass an int argument pthread_t thread; // Declare a pthread_t variable pthread_attr_t attr; // Declare a pthread_attr_t variable pthread_attr_init(&attr); // Initialize the thread attributes with default values int n = 10; // Define an int argument for the thread function int rc = pthread_create(&thread, &attr, square, &n); // Create the thread and pass the address of n as the argument // Join the thread and get the int value returned by the thread function void *status; // Declare a void pointer for the thread exit status int rc = pthread_join(thread, &status); // Join the thread int result = (int) status; // Cast the thread exit status to an int value printf("The square of %d is %d\n", n, result); // Print the result


Synchronizing threads with mutexes and condition variables




To synchronize threads with mutexes and condition variables, you need to use the pthread_mutex and pthread_cond functions. A mutex is a mutual exclusion object that allows only one thread at a time to access a shared resource. A condition variable is a synchronization object that allows threads to wait for a certain condition to occur. For example:


// Define a global variable that will be shared by multiple threads int count = 0; // Define a mutex and a condition variable for synchronizing access to count = PTHREAD_MUTEX_INITIALIZER; // Initialize the mutex with default values pthread_cond_t cond = PTHREAD_COND_INITIALIZER; // Initialize the condition variable with default values // Define a function that will be executed by a producer thread void *produce(void *arg) int n = *(int *) arg; // Cast the argument to an int pointer and dereference it for (int i = 0; i


Using other features of POSIX Threads




POSIX Threads also provide other features that can be useful for parallel programming such as thread attributes, thread cancellation, thread-specific data, read-write locks, barriers, and spinlocks. Here are some brief descriptions of these features:


  • Thread attributes: Thread attributes are properties that can be set or modified for each thread. Some examples of thread attributes are stack size, scheduling policy, detach state, etc. To use thread attributes, you need to use the pthread_attr functions such as pthread_attr_init, pthread_attr_setstacksize, pthread_attr_setschedpolicy, etc.



  • Thread cancellation: Thread cancellation is a mechanism that allows one thread to terminate another thread. To use thread cancellation, you need to use the pthread_cancel function to send a cancellation request to a target thread, and the pthread_testcancel function to check if a cancellation request has been received. You can also use the pthread_setcancelstate and pthread_setcanceltype functions to control how a thread responds to cancellation requests.



  • Thread-specific data: Thread-specific data is a mechanism that allows each thread to have its own copy of a global variable. To use thread-specific data, you need to use the pthread_key functions such as pthread_key_create, pthread_setspecific, pthread_getspecific, etc.



  • Read-write locks: Read-write locks are synchronization objects that allow multiple threads to read from a shared resource concurrently, but only one thread to write to it at a time. To use read-write locks, you need to use the pthread_rwlock functions such as pthread_rwlock_init, pthread_rwlock_rdlock, pthread_rwlock_wrlock, etc.



  • Barriers: Barriers are synchronization objects that allow multiple threads to wait for each other at a certain point in the program. To use barriers, you need to use the pthread_barrier functions such as pthread_barrier_init, pthread_barrier_wait, etc.



  • Spinlocks: Spinlocks are synchronization objects that are similar to mutexes, but they use busy-waiting instead of blocking. To use spinlocks, you need to use the pthread_spin functions such as pthread_spin_init, pthread_spin_lock, etc.



How to download a PDF book on programming with POSIX Threads




Finding a reliable source for the PDF book




If you want to download a PDF book on programming with POSIX Threads, you need to find a reliable source that provides high-quality and up-to-date information. Here are some criteria for finding a reliable source for the PDF book:


  • Author credentials: The author of the PDF book should have relevant qualifications and experience in the field of parallel programming and POSIX Threads. You can check the author's bio, publications, affiliations, etc. to verify their credentials.



  • Publication date: The publication date of the PDF book should be recent enough to reflect the current state of the art and standards of POSIX Threads. You can check the publication date on the cover page, the preface, or the bibliography of the PDF book.



Reviews: The reviews of the PDF book should be positive and constructive, indicating that the PDF book is well-written, well-organized, well-explained, and well-researched. You can check the reviews on online platforms such as Amazon, Goodrea


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