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: http://oit.cmc.msu.ru/php/ref.sem.html
Дата изменения: Sun Feb 3 22:54:31 2002 Дата индексирования: Mon Oct 1 19:54:50 2012 Кодировка: |
This module provides semaphore functions using System V semaphores. Semaphores may be used to provide exclusive access to resources on the current machine, or to limit the number of processes that may simultaneously use a resource.
This module provides also shared memory functions using System V shared memory. Shared memory may be used to provide access to global variables. Different httpd-daemons and even other programs (such as Perl, C, ...) are able to access this data to provide a global data-exchange. Remember, that shared memory is NOT safe against simultaneous access. Use semaphores for synchronization.
Table 1. Limits of Shared Memory by the Unix OS
SHMMAX | max size of shared memory, normally 131072 bytes |
SHMMIN | minimum size of shared memory, normally 1 byte |
SHMMNI | max amount of shared memory segments on a system, normally 100 |
SHMSEG | max amount of shared memory segments per process, normally 6 |
Note: These functions do not work on Windows systems.