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This module provides wrappers for the System V IPC family of functions. It includes semaphores, shared memory and inter-process messaging (IPC).
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.
Tabela 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 |
The messaging functions may be used to send and receive messages to/from other processes. They provide a simple and effective means of exchanging data between processes, without the need for setting up an alternative using Unix domain sockets.
Notatka: To rozszerzenie nie jest dostępne na platformie Windows.
Do zbudowania tego rozszerzenia nie są wymagane żadne zewnętrzne biblioteki.
Support for this functions are not enabled by default. To enable System V semaphore support compile PHP with the option --enable-sysvsem. To enable the System V shared memory support compile PHP with the option --enable-sysvshm. To enable the System V messages support compile PHP with the option --enable-sysvmsg.
Na działanie tych funcji wpływają ustawienia zawarte w pliku php.ini.
Tabela 2. Semaphore Configuration Options
Name | Default | Changeable | Changelog |
---|---|---|---|
sysvmsg.value | "42" | PHP_INI_ALL | |
sysvmsg.string | "foobar" | PHP_INI_ALL |
Poniższe stałe są zdefiniowane w tym rozszerzeniu i stają się dostępne, gdy rozszerzenie jest dokompilowane do PHP, lub załadowane dynamicznie przy starcie.
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Generated: 2007-01-26 18:02:40