Unix IPC primitives
Semaphores
System V semaphores
creation: semget
down and up: semop
other operations: semctl
execute man semget, man semop or man semctl for a description
POSIX semaphores
Two types: named and unnamed semaphores.
Named semaphores.
sem_open, sem_close, sem_unlink
created in a virtual filesystem (e.g., /dev/sem).
unnamed semaphores – memory based
sem_init, sem_destroy
down and up.
sem_wait, sem_trywait, sem_timedwait, sem_post
execute man sem_overview for an overview.
Shared memory
Address spaces of processes are independent.
But address spaces are virtual.
The same physical region can be mapped into two or more virtual regions.
This is managed as a resource by the operating system.
System V shared memory
creation – shmget
mapping and unmapping – shmat, shmdt
other operations – shmctl
execute man shmget, man shmat man shmdt or man shmctl for a description.
POSIX shared memory
creation - shm open, ftruncate
mapping and unmapping - mmap, munmap
other operations - close, shm unlink, fchmod,...
execute man shm_overview for an overview
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