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.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
.\"
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
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.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" Japanese Version Copyright (c) 2006 Akihiro MOTOKI all rights reserved.
.\" Translated 2006-04-18, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2009-02-23, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.19
.\"
.TH SEM_OPEN 3 2009-02-20 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH ̾Á°
.\"O sem_open \- initialize and open a named semaphore
sem_open \- ̾Á°ÉÕ¤­¥»¥Þ¥Õ¥©¤ò½é´ü²½¤·¡¢¥ª¡¼¥×¥ó¤¹¤ë
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.BR "#include <fcntl.h>" "           /* For O_* constants */"
.BR "#include <sys/stat.h>" "        /* For mode constants */"
.B #include <semaphore.h>
.sp
.BI "sem_t *sem_open(const char *" name ", int " oflag );
.BI "sem_t *sem_open(const char *" name ", int " oflag ", "
.BI "                mode_t " mode ", unsigned int " value );
.fi
.sp
.\"O Link with \fI\-lrt\fP or \fI\-pthread\fP.
\fI\-lrt\fP ¤Þ¤¿¤Ï \fI\-pthread\fP ¤Ç¥ê¥ó¥¯¤¹¤ë¡£
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O .BR sem_open ()
.\"O creates a new POSIX semaphore or opens an existing semaphore.
.\"O The semaphore is identified by
.\"O .IR name .
.\"O For details of the construction of
.\"O .IR name ,
.\"O see
.\"O .BR sem_overview (7).
.BR sem_open ()
¤Ï¡¢¿·µ¬¤Î POSIX ¥»¥Þ¥Õ¥©¤òºîÀ®¤¹¤ë¤«¡¢´û¸¤Î¥»¥Þ¥Õ¥©¤Î¥ª¡¼¥×¥ó¤ò¹Ô¤¦¡£
¥»¥Þ¥Õ¥©¤Ï
.I name
¤Ç¼±Ê̤µ¤ì¤ë¡£
.I name
¤Î¹½À®¤Î¾ÜºÙ¤Ï
.BR sem_overview (7)
¤ò»²¾È¡£

.\"O The
.\"O .I oflag
.\"O argument specifies flags that control the operation of the call.
.\"O (Definitions of the flags values can be obtained by including
.\"O .IR <fcntl.h> .)
.I oflag
°ú¤­¿ô¤Ë¤Ï¡¢
.BR sem_open ()
¤ÎÆ°ºî¤òÀ©¸æ¤¹¤ë¥Õ¥é¥°¤ò»ØÄꤹ¤ë
(oflag ¤ÎÃͤÎÄêµÁ¤Ï
.I <fcntl.h>
¤Î¥¤¥ó¥¯¥ë¡¼¥É¤Ë¤è¤êÆÀ¤é¤ì¤ë)¡£
.\"O If
.\"O .B O_CREAT
.\"O is specified in
.\"O .IR oflag ,
.\"O then the semaphore is created if
.\"O it does not already exist.
.\"O The owner (user ID) of the semaphore is set to the effective
.\"O user ID of the calling process.
.\"O The group ownership (group ID) is set to the effective group ID
.\"O of the calling process.
.\"O .\" In reality the file system IDs are used on Linux.
.I oflag
¤Ë
.B O_CREAT
¤¬»ØÄꤵ¤ì¤ë¤È¡¢¤Þ¤À¸ºß¤·¤Ê¤¤¾ì¹ç¤Ë¤Ï¤½¤Î¥»¥Þ¥Õ¥©¤¬ºîÀ®¤µ¤ì¤ë¡£
¥»¥Þ¥Õ¥©¤Î½êÍ­¼Ô (¥æ¡¼¥¶ ID)¡¢¥°¥ë¡¼¥×½êÍ­¸¢ (¥°¥ë¡¼¥× ID) ¤Ë¤Ï¡¢
¤½¤ì¤¾¤ì¸Æ¤Ó½Ð¤·¸µ¥×¥í¥»¥¹¤Î¼Â¸ú UID¡¢¼Â¸ú GID ¤¬ÀßÄꤵ¤ì¤ë¡£
.\" ¼ÂºÝ¤Ï¡¢Linux ¤Ç¤Ï¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à ID ¤¬»ÈÍѤµ¤ì¤ë¡£
.\"O If both
.\"O .B O_CREAT
.\"O and
.\"O .B O_EXCL
.\"O are specified in
.\"O .IR oflag ,
.\"O then an error is returned if a semaphore with the given
.\"O .I name
.\"O already exists.
.I oflag
¤Ë
.B O_CREAT
¤È
.B O_EXCL
¤ÎξÊý¤¬»ØÄꤵ¤ì¤¿¾ì¹ç¡¢»ØÄꤵ¤ì¤¿Ì¾Á°
.I name
¤Î¥»¥Þ¥Õ¥©¤¬¤¹¤Ç¤Ë¸ºß¤¹¤ë¤È¥¨¥é¡¼¤¬ÊÖ¤µ¤ì¤ë¡£
.PP
.\"O If
.\"O .B O_CREAT
.\"O is specified in
.\"O .IR oflag ,
.\"O then two additional arguments must be supplied.
.I oflag
¤Ë
.B O_CREAT
¤ò»ØÄꤹ¤ë¾ì¹ç¡¢¤µ¤é¤Ë°ú¤­¿ô¤¬ 2 ¤ÄɬÍפǤ¢¤ë¡£
.\"O The
.\"O .I mode
.\"O argument specifies the permissions to be placed on the new semaphore,
.\"O as for
.\"O .BR open (2).
.\"O (Symbolic definitions for the permissions bits can be obtained by including
.\"O .IR <sys/stat.h> .)
.\"O The permissions settings are masked against the process umask.
.\"O Both read and write permission should be granted to each class of
.\"O user that will access the semaphore.
.I mode
°ú¤­¿ô¤Ï¡¢
.BR open (2)
¤ÈƱ¤¸¤è¤¦¤Ë¡¢¿·¤·¤¤¥»¥Þ¥Õ¥©¤ËÀßÄꤵ¤ì¤ë¥¢¥¯¥»¥¹µö²Ä (permission) ¤ò
»ØÄꤹ¤ë¡£µö²ÄÀßÄê¤Ï¥×¥í¥»¥¹¤Î umask ¤Ç¥Þ¥¹¥¯¤µ¤ì¤ë
(µö²Ä¥Ó¥Ã¥È¤Î¥·¥ó¥Ü¥ëÄêµÁ¤Ï
.I <sys/stat.h>
¤Î¥¤¥ó¥¯¥ë¡¼¥É¤Ë¤è¤êÆÀ¤é¤ì¤ë)¡£
¥»¥Þ¥Õ¥©¤Ë¥¢¥¯¥»¥¹¤·¤è¤¦¤È¤¹¤ë¥æ¡¼¥¶¤Ï¡¢Æɤ߽Ф·µö²Ä¤È½ñ¤­¹þ¤ßµö²Ä¤Î
ξÊý¤òÆÀ¤ëɬÍפ¬¤¢¤ë¡£
.\"O The
.\"O .I value
.\"O argument specifies the initial value for the new semaphore.
.\"O If
.\"O .B O_CREAT
.\"O is specified, and a semaphore with the given
.\"O .I name
.\"O already exists, then
.\"O .I mode
.\"O and
.\"O .I value
.\"O are ignored.
.I value
°ú¤­¿ô¤Ï¿·¤·¤¤¥»¥Þ¥Õ¥©¤Î½é´üÃͤò»ØÄꤹ¤ë¡£
.B O_CREAT
¤¬»ØÄꤵ¤ì¡¢»ØÄꤷ¤¿Ì¾Á°
.I name
¤Î¥»¥Þ¥Õ¥©¤¬¤¹¤Ç¤Ë¸ºß¤¹¤ë¾ì¹ç¡¢
.I mode
¤È
.I value
¤Ï̵»ë¤µ¤ì¤ë¡£
.\"O .SH RETURN VALUE
.SH ÊÖ¤êÃÍ
.\"O On success,
.\"O .BR sem_open ()
.\"O returns the address of the new semaphore;
.\"O this address is used when calling other semaphore-related functions.
.\"O On error,
.\"O .BR sem_open ()
.\"O returns
.\"O .BR SEM_FAILED ,
.\"O with
.\"O .I errno
.\"O set to indicate the error.
À®¸ù¤¹¤ë¤È¡¢
.BR sem_open ()
¤Ï¿·¤·¤¤¥»¥Þ¥Õ¥©¤Î¥¢¥É¥ì¥¹¤òÊÖ¤¹¡£
¤³¤Î¥¢¥É¥ì¥¹¤Ï¾¤Î¥»¥Þ¥Õ¥©´ØÏ¢¤Î´Ø¿ô¤ò¸Æ¤Ó½Ð¤¹ºÝ¤Ë»ÈÍѤµ¤ì¤ë¡£
¥¨¥é¡¼¤Î¾ì¹ç¡¢
.BR sem_open ()
¤Ï
.B SEM_FAILED
¤òÊÖ¤·¡¢
.I errno
¤Ë¥¨¥é¡¼¤ò¼¨¤¹Ãͤò¥»¥Ã¥È¤¹¤ë¡£
.\"O .SH ERRORS
.SH ¥¨¥é¡¼
.TP
.B EACCES
.\"O The semaphore exists, but the caller does not have permission to
.\"O open it.
¤½¤Î¥»¥Þ¥Õ¥©¤¬Â¸ºß¤¹¤ë¤¬¡¢¸Æ¤Ó½Ð¤·¸µ¤Ë¤Ï¤½¤Î¥»¥Þ¥Õ¥©¤ò¥ª¡¼¥×¥ó¤¹¤ë
µö²Ä¤¬¤Ê¤¤¡£
.TP
.B EEXIST
.\"O Both
.\"O .B O_CREAT
.\"O and
.\"O .B O_EXCL
.\"O were specified in
.\"O .IR oflag ,
.\"O but a semaphore with this
.\"O .I name
.\"O already exists.
.I oflag
¤Ë
.B O_CREAT
¤È
.B O_EXCL
¤ÎξÊý¤¬»ØÄꤵ¤ì¤¿¤¬¡¢
.I name
¤È¤¤¤¦Ì¾Á°¤Î¥»¥Þ¥Õ¥©¤Ï¤¹¤Ç¤Ë¸ºß¤¹¤ë¡£
.TP
.B EINVAL
.\"O .I value
.\"O was greater than
.\"O .BR SEM_VALUE_MAX .
.I value
¤¬
.B SEM_VALUE_MAX
¤è¤ê¤âÂ礭¤¤¡£
.TP
.B EINVAL
.\"O .I name
.\"O consists of just "/", followed by no other characters.
.I name
¤¬ "/" ¤À¤±¤Ç¹½À®¤µ¤ì¡¢¤½¤Î¸å¤í¤Ë¾¤Îʸ»ú¤¬Â³¤¤¤Æ¤¤¤Ê¤«¤Ã¤¿¡£
.TP
.B EMFILE
.\"O The process already has the maximum number of files and open.
¥ª¡¼¥×¥ó¤µ¤ì¤¿¥Õ¥¡¥¤¥ë¿ô¤¬¤¹¤Ç¤Ë¤½¤Î¥×¥í¥»¥¹¤Ë¤ª¤±¤ë¾å¸Â¤Ë㤷¤Æ¤¤¤ë¡£
.TP
.B ENAMETOOLONG
.\"O .I name
.\"O was too long.
.I name
¤¬Ä¹¤¹¤®¤ë¡£
.TP
.B ENFILE
.\"O The system limit on the total number of open files has been reached.
¥ª¡¼¥×¥ó¤µ¤ì¤¿¥Õ¥¡¥¤¥ëÁí¿ô¤¬¥·¥¹¥Æ¥àÁ´ÂΤǤξå¸Â¤Ë㤷¤Æ¤¤¤ë¡£
.TP
.B ENOENT
.\"O The
.\"O .B O_CREAT
.\"O flag was not specified in
.\"O .IR oflag
.\"O and no semaphore with this
.\"O .I name
.\"O exists;
.I oflag
¤Ë
.B O_CREAT
¥Õ¥é¥°¤¬»ØÄꤵ¤ì¤Æ¤ª¤é¤º¡¢
.I name
¤È¤¤¤¦Ì¾Á°¤Î¥»¥Þ¥Õ¥©¤â¸ºß¤·¤Ê¤¤¡£
.\"O or,
¤Þ¤¿¤Ï¡¢
.\" this error can occur if we have a name of the (nonportable) form
.\" /dir/name, and the directory /dev/shm/dir does not exist.
.\"O .B O_CREAT
.\"O was specified, but
.\"O .I name
.\"O wasn't well formed.
.B O_CREAT
¤¬»ØÄꤵ¤ì¤¿¤¬¡¢
.I name
¤¬Å¬ÀڤʷÁ¼°¤Ç¤Ï¤Ê¤«¤Ã¤¿¡£
.TP
.B ENOMEM
.\"O Insufficient memory.
½½Ê¬¤Ê¥á¥â¥ê¤¬¤Ê¤¤¡£
.\"O .SH CONFORMING TO
.SH ½àµò
POSIX.1-2001.
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR sem_close (3),
.BR sem_getvalue (3),
.BR sem_post (3),
.BR sem_unlink (3),
.BR sem_wait (3),
.BR sem_overview (7)