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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@146503 c90b9560-bf6c-de11-be94-00142212c4b1
109 lines
3.7 KiB
XML
109 lines
3.7 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.5 $ -->
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<!-- splitted from ./en/functions/shmop.xml, last change in rev 1.12 -->
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<refentry id="function.shmop-open">
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<refnamediv>
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<refname>shmop_open</refname>
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<refpurpose>Create or open shared memory block</refpurpose>
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</refnamediv>
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<refsect1>
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<title>Description</title>
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<methodsynopsis>
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<type>int</type><methodname>shmop_open</methodname>
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<methodparam><type>int</type><parameter>key</parameter></methodparam>
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<methodparam><type>string</type><parameter>flags</parameter></methodparam>
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<methodparam><type>int</type><parameter>mode</parameter></methodparam>
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<methodparam><type>int</type><parameter>size</parameter></methodparam>
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</methodsynopsis>
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<para>
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<function>shmop_open</function> can create or open a shared memory block.
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</para>
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<para>
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<function>shmop_open</function> takes 4 parameters: key, which is the
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system's id for the shared memory block, this parameter can be passed
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as a decimal or hex. The second parameter are the flags that you can use:
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<itemizedlist>
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<listitem>
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<simpara>
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"a" for access (sets SHM_RDONLY for shmat)
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use this flag when you need to open an existing shared memory
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segment for read only
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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"c" for create (sets IPC_CREATE)
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use this flag when you need to create a new shared memory segment
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or if a segment with the same key exists, try to open it for read
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and write
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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"w" for read & write access
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use this flag when you need to read and write to a shared memory
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segment, use this flag in most cases.
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</simpara>
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</listitem>
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<listitem>
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<simpara>
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"n" create a new memory segment (sets IPC_CREATE|IPC_EXCL)
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use this flag when you want to create a new shared memory segment
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but if one already exists with the same flag, fail. This is useful
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for security purposes, using this you can prevent race condition
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exploits.
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</simpara>
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</listitem>
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</itemizedlist>
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The third parameter is the mode, which are the permissions that you
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wish to assign to your memory segment, those are the same as permission
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for a file. Permissions need to be passed in octal form ex. 0644.
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The last parameter is size of the shared memory block you wish to create
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in bytes.
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<note><simpara>
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Note: the 3rd and 4th should be entered as 0 if you are opening an
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existing memory segment. On success <function>shmop_open</function> will
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return an id that you can use to access the shared memory segment
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you've created.
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</simpara></note>
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</para>
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<para>
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<example>
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<title>Create a new shared memory block</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$shm_key = ftok(__FILE__, 't');
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$shm_id = shmop_open($shm_key, "c", 0644, 100);
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?>
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]]>
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</programlisting>
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</example>
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</para>
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<para>
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This example opened a shared memory block with a system id returned by
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<function>ftok</function>.
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</para>
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</refsect1>
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</refentry>
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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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