Initializing Semaphores

• Allocating and initializing semaphores are two separate operations.
  • To initialize a semaphore, use semctl with zero as the second argument,
  • SETALL as the third argument,
  • For the fourth argument, you must create a union semun object and point its array field at an array of unsigned short values. Each value is used to initialize one semaphore in the set.
• The following http://siber.cankaya.edu.tr/SystemsProgramming/cfiles/sem_init.ccode (see Fig. 1.2.2) presents a function that initializes a binary semaphore.

  Figure 5: Initializing a Binary Semaphore