'\" t
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.\" Japanese Version Copyright (c) 2006 Akihiro MOTOKI all rights reserved.
.\" Translated 2006-04-18, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2008-08-07, Akihiro MOTOKI, LDP v3.05
.\" Updated 2009-02-23, Akihiro MOTOKI, LDP v3.19
.\"
.TH SEM_OVERVIEW 7 2009-02-25 "Linux" "Linux Programmer's Manual"
.SH ̾
sem_overview \- POSIX ޥեγ
.SH 
POSIX ޥեѤȡץ䥹åɴ֤Ǥư
Ʊ뤳ȤǤ롣

ޥեǤꡢͤϷ褷 0 ̤ˤʤ뤳Ȥϵʤ
ޥեФƤǤ 2 ĤǤ:
ޥեͤ 1 䤹
.RB ( sem_post (3));
ޥեͤ 1 餹
.RB ( sem_wait (3))
ޥեͤǤ 0 ξ硢ޥեͤ 0 礭ʤޤ
.BR sem_wait (3)
 (block) 롣

POSIX ޥեˤϡ̾դޥե (named semaphore) 
̾ʤޥե (unnamed semaphore)  2Ĥη롣
.TP
.B ̾դޥե
̾դޥե
.I /somename
Ȥ̾Ǽ̤롣
̾ϡ
.BI NAME_MAX \-4
(ʤ 251) ʸ NULL ü줿ʸǡ
.\" glibc allows the initial slash to be omitted, and makes
.\" multiple initial slashes equivalent to a single slash.
.\" This differs from the implementation of POSIX message queues.
åǻϤޤꡢåʳʸ 1 ʸʾ³Ǥ롣
.\" glibc allows subdirectory components in the name, in which
.\" case the subdirectory tree must exist under /dev/shm, and
.\" the fist subdirectory component must exist as the name
.\" sem.name, and all of the subdirectory components must allow the
.\" required permissions if a user wants to create a semaphore
.\" object in a subdirectory.
.BR sem_open (3)
Ʊ̾ϤȤˤꡢ2 ĤΥץ֤Ʊ̾Υޥե
ФԤȤǤ롣

.BR sem_open (3)
ؿϡ̾դޥե뤫¸ߤ̾դ
ޥե򥪡ץ󤹤롣
ޥե򥪡ץ󤷤ϡ
.BR sem_post (3)

.BR sem_wait (3)
ȤäƥޥեǤ롣
ץޥեλѤ򽪤ݤϡ
.BR sem_close (3)
Ȥäƥޥե򥯥Ǥ롣
륻ޥեɤΥץѤʤʤȡ
.BR sem_unlink (3)
ȤäƤΥޥե򥷥ƥफ뤳ȤǤ롣
.TP
.B ̾ʤޥե (١ޥե)
̾ʤޥե̾ʤꡢޥեϡ
ʣåɴ֤Ƕͭ줿ΰ衢⤷ʣץ֤
ͭ줿ΰ֤ (Ԥ
.IR "åɶͭޥե (thread-shared semaphore)" 
Ԥ
.IR "ץͭޥե (process-shared semaphore)"
ȸƤ)åɶͭޥեϡƱץΥåɴ֤Ƕͭ줿
ΰ衢㤨ѿ (global variable) ֤롣
ץͭޥեϡͭΰ (㤨С
.BR semget (2)
ȤäƺǤ System V ͭꡦȤ
.BR shm_open (3)
ȤäƺǤ POSIX ͭꡦ֥)
֤ʤФʤʤ

̾ʤޥեϡѤ
.BR sem_init (3)
ȤäƽʤФʤʤ
ޥե
.BR sem_post (3)

.BR sem_wait (3)
ȤäǤ롣
ޥեϤɬפʤʤäȤ䡢
ޥե֤Ƥˤϡ
.BR sem_destroy (3)
Ȥäƥޥե˴٤Ǥ롣
.PP
λĤǤϡPOSIX ޥե Linux μξܺ
ˤĤ롣
.SS С
С 2.6 ΥͥǤϡLinux 
̾ʤΥåɶͭޥեΤߤ򥵥ݡȤƤ
Linux 2.6  NPTL åɼ󶡤Ƥ glibc ä
ƥǤϡPOSIX ޥեδʼ󶡤롣
.SS ³
POSIX ̾դޥեϥͥݻ롣
.BR sem_unlink (3)
ǺʤСޥե
ƥबåȥ󤵤ޤ¸ߤ³롣
.SS 
POSIX ޥե API Ѥץ
.I cc \-lrt
ǥѥ뤷ꥢ륿饤֥
.I librt
ȥ󥯤ʤФʤʤ
.SS ե륷ƥͳǤ̾դޥեؤΥ
Linux Ǥϡ̾դޥեϲۥե륷ƥ
(virtual file system) 
.I \fBsem.\fPsomename
Ȥ̾Ǻ롣ۥե륷ƥ̾
.I /dev/shm
ʲ˥ޥȤ롣
(줬ޥե̾ʸξ¤
.B NAME_MAX
ǤϤʤ
.BI NAME_MAX \-4
ȤʤäƤͳǤ롣)

Linux 2.6.19 ʹߤǤϡΥǥ쥯ȥ۲ΥեФ ACL 
Ǥ֥ȤؤεĤ桼ñ̡롼ñ̤椹뤳Ȥ
Ǥ롣
.SH 
POSIX.1-2001.
.SH 
System V ޥե
.RB ( semget (2),
.BR semop (2)
ʤ) ϸŤޥե API Ǥ롣 POSIX ޥե System V 
ñǡޤ߷פ줿󥿥ե󶡤Ƥ롣
ǡPOSIX ޥե System V ޥե٤
ѤǤ륷ƥबʤ (äˡŤƥǤϾʤ)
.SH 
Ƽ POSIX ޥեؿѤ㤬
.BR sem_wait (3)
˵ܤƤ롣
.SH Ϣ
.BR sem_close (3),
.BR sem_destroy (3),
.BR sem_getvalue (3),
.BR sem_init (3),
.BR sem_open (3),
.BR sem_post (3),
.BR sem_unlink (3),
.BR sem_wait (3),
.BR pthreads (7)