Linux-style, since it is what is described in Steven's Unix Network Programming book. Here is the Linux-style union semun, along with the semctl() call that will destroy the semaphore: union semun { Linux/UNIX System Programming POSIX Shared Memory Michael Kerrisk, man7.org c 2015 February 2015 Outline 22 POSIX Shared Memory 22-1 22.1 Overview 22-3 Commonly, semaphores are used Linux/UNIX System Programming c 2015, Michael Kerrisk POSIX Shared Memory 22-5 §22.1 A Linux semaphore data structure contains the following information: The stylized page/paper, as well as the terms "The Linux Tutorial", "The Linux Server Tutorial", "The Linux Knowledge Base and Tutorial" and "The place where you learn Linux" are service marks of James Mohr. All rights Semaphores are clubbed with message queues and shared memory under the Interprocess Communication (IPC) facilities in Unix-like systems such as Linux. There are two varieties of semaphores, the traditional System V semaphores and the newer POSIX semaphores. In this post we will look at the POSIX semaphores. 2.0 POSIX Semaphores sem_overview - overview of POSIX semaphores Linux supported only unnamed, thread-shared semaphores. On a system with Linux 2.6 and a glibc that provides the NPTL threading implementation, a complete implementation of POSIX semaphores is provided. Semaphore is a hardware or software flag. In programming, especially in UNIX systems, semaphores are a technique for coordinating or synchronizing activities in which multiple process compete for the same operating system resources. In multitasking systems, a semaphore is a variable with a value that indicates the status of a common resource. Semaphore tutorial? - UNIX Programming. Does anybody have a good tutorial for how SysV semaphores work, specifically the semop() function? I've read the description in Stevens' Unix Network Programming several times, but I'm still totally baffled. This tutorial has explored the very basics of multithreade