62 lines
2.5 KiB
HTML
62 lines
2.5 KiB
HTML
<html><!-- This HTML file has been created by texi2html 1.29
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from syscalls.texi on 4 June 1994 -->
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<TITLE>Syscall specifications of Linux - semget</TITLE>
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<P>Go to the <A HREF="syscalls_77.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_77.html">previous</A>, <A HREF="syscalls_79.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_79.html">next</A> section.<P>
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<H2><A NAME="SEC78" HREF="syscalls_toc.html#SEC78" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_toc.html#SEC78">semget</A></H2>
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<P>
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<H3>SYNOPSIS</H3>
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<P>
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<CODE>int semget(key_t <VAR>key</VAR>, int <VAR>nsems</VAR>, int <VAR>semflg</VAR>);</CODE>
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<H3>PARAMETERS</H3>
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<P>
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<VAR>key</VAR>: [in] the semaphore set identificator.
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<P>
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<VAR>nsems</VAR>: [in] the number of semaphore in the set.
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<P>
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<VAR>semflg</VAR>: [in] flags (see description).
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<P>
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<H3>DESCRIPTION</H3>
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<P>
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Gets a semaphore set identifier. If <VAR>key</VAR> is <CODE>IPC_PRIVATE</CODE>, a
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new set is created. Otherwise, the result depends on the value of
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<VAR>semflg</VAR>:
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<P>
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<DL COMPACT>
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<DT><CODE>IPC_CREAT</CODE>
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<DD>creates a new queue for the key if it does not already exist.
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<P>
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<DT><CODE>IPC_EXCL</CODE>
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<DD>if there is already a existing queue associated with <VAR>key</VAR>, the call
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fails.
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</DL>
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<P>
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The 9 lower bits of <VAR>semflg</VAR> specify the permission bits of the new
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set. They have the same layout and meaning as those for files.
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However, the execute permissions are meaningless for sets.
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<P>
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When creating a set the system sets the appropriate parameters in the
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<CODE>semid_ds</CODE> structure associated with the new set. When accessing
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an already existing set, the system simply check if the set can be
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accessed.
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<P>
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<H3>RETURN VALUE</H3>
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<P>
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On success, the call returns the new semaphore set identificator. On
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error -1 is returned and <CODE>errno</CODE> is set to one of the following
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values:
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<P>
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<UL>
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<LI><CODE>EACCESS</CODE>: the task has no access permission to the set.
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<LI><CODE>EEXIST</CODE>: <CODE>IPC_CREAT</CODE> and <CODE>IPC_EXCL</CODE> were specified
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and the set already exists.
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<LI><CODE>EIDRM</CODE>: the set no longer exists in the system.
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<LI><CODE>ENOENT</CODE>: the set never existed.
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<LI><CODE>ENOSPC</CODE>: the maximum number of semaphore sets for the system
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has been reached.
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<LI><CODE>ENOMEM</CODE>
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</UL>
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<P>
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<P>Go to the <A HREF="syscalls_77.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_77.html">previous</A>, <A HREF="syscalls_79.html" tppabs="http://www.infran.ru/TechInfo/syscalls/syscalls_79.html">next</A> section.<P>
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