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https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@97548 c90b9560-bf6c-de11-be94-00142212c4b1
124 lines
3.5 KiB
XML
124 lines
3.5 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.8 $ -->
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<reference id="ref.sem">
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<title>Semaphore, Shared Memory and IPC Functions</title>
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<titleabbrev>Semaphore</titleabbrev>
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<partintro>
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<section id="sem.intro">
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&reftitle.intro;
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<para>
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This module provides wrappers for the System V IPC family of functions.
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It includes semaphores, shared memory and inter-process messaging (IPC).
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</para>
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<para>
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Semaphores may be used to provide exclusive access to
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resources on the current machine, or to limit the number of
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processes that may simultaneously use a resource.
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</para>
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<para>
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This module provides also shared memory functions using System V
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shared memory. Shared memory may be used to provide access to
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global variables. Different httpd-daemons and even other programs
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(such as Perl, C, ...) are able to access this data to provide a
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global data-exchange. Remember, that shared memory is NOT safe
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against simultaneous access. Use semaphores for synchronization.
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<table>
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<title>Limits of Shared Memory by the Unix OS</title>
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<tgroup cols="2">
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<tbody>
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<row>
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<entry>SHMMAX</entry>
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<entry>max size of shared memory, normally 131072 bytes</entry>
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</row>
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<row>
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<entry>SHMMIN</entry>
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<entry>minimum size of shared memory, normally 1 byte</entry>
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</row>
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<row>
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<entry>SHMMNI</entry>
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<entry>
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max amount of shared memory segments on a system,
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normally 100
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</entry>
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</row>
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<row>
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<entry>SHMSEG</entry>
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<entry>
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max amount of shared memory segments per process, normally 6
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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<para>
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The messaging functions may be used to send and receive messages to/from
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other processes. They provide a simple and effective means of exchanging
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data between processes, without the need for setting up an alternative
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using unix domain sockets.
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</para>
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<note>
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<simpara>
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These functions do not work on Windows systems.
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</simpara>
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</note>
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</section>
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<section id="sem.requirements">
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&reftitle.required;
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&no.requirement;
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</section>
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<section id="sem.installation">
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&reftitle.install;
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<para>
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Support for this functions are not enabled by default.
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To enable System V semaphore support compile PHP with the option
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<option role="configure">--enable-sysvsem</option>.
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To enable the System V shared memory support compile PHP with the option
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<option role="configure">--enable-sysvshm</option>.
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To enable the System V messages support compile PHP with the option
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<option role="configure">--enable-sysvmsg</option>.
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</para>
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</section>
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&reference.sem.ini;
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<section id="sem.resources">
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&reftitle.resources;
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<para>
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</para>
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</section>
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<section id="sem.constants">
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&reftitle.constants;
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&no.constants;
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</section>
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</partintro>
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&reference.sem.functions;
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</reference>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"../../../manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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