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.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
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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>
.\"
.TH SEM_GETVALUE 3 2006-03-25 "Linux" "Linux Programmer's Manual"
.\"O .SH NAME
.SH 名前
.\"O sem_getvalue \- get the value of a semaphore
sem_getvalue \- セマフォの値を取得する
.\"O .SH SYNOPSIS
.SH 書式
.nf
.B #include <semaphore.h>
.sp
.BI "int sem_getvalue(sem_t *" sem ", int *" sval );
.fi
.sp
.\"O Link with \fI\-lrt\fP or \fI\-pthread\fP.
\fI\-lrt\fP または \fI\-pthread\fP でリンクする。
.\"O .SH DESCRIPTION
.SH 説明
.\"O .BR sem_getvalue ()
.\"O places the current value of the semaphore pointed to
.\"O .I sem
.\"O into the integer pointed to by
.\"O .IR sval .
.BR sem_getvalue ()
は、
.I sem
が指すセマフォの現在の値を
.I sval
で指す整数に格納する。

.\"O If one or more processes or threads are blocked
.\"O waiting to lock the semaphore with
.\"O .BR sem_wait (3),
.\"O POSIX.1-2001 permits two possibilities for the value returned in
.\"O .IR sval :
.\"O either 0 is returned;
.\"O or a negative number whose absolute value is the count
.\"O of the number of processes and threads currently blocked in
.\"O .BR sem_wait (3).
.\"O Linux adopts the former behavior.
POSIX.1-2001 によると、
1つ以上のプロセスかスレッドが
.BR sem_wait (3)
でセマフォのロック待ちで停止している場合、
.I sval
で返される値は 0 もしくは負の値のいずれかとなる。
負の値の場合、その絶対値は
.BR sem_wait (3)
で現在停止しているプロセスかスレッドの合計数に等しい。
Linux は前者の動作 (0 を返す動作) を採用している。
.\"O .SH RETURN VALUE
.SH 返り値
.\"O .BR sem_getvalue ()
.\"O returns 0 on success;
.\"O on error, \-1 is returned and
.\"O .I errno
.\"O is set to indicate the error.
成功すると、
.BR sem_getvalue ()
は 0 を返す。エラーの場合、\-1 を返し、
.I errno
にエラーを示す値をセットする。
.\"O .SH ERRORS
.SH エラー
.TP
.B EINVAL
.\"O .I sem
.\"O is not a valid semaphore.
.I sem
は有効なセマフォではない。
.\"O .SH CONFORMING TO
.SH 準拠
POSIX.1-2001.
.\"O .SH NOTES
.SH 注意
.\"O The value of the semaphore may already have changed by the time
.\"O .BR sem_getvalue ()
.\"O returns.
.BR sem_getvalue ()
が返るときには、すでにセマフォの値は変化している可能性がある。
.\"O .SH "SEE ALSO"
.SH 関連項目
.BR sem_post (3),
.BR sem_wait (3),
.BR sem_overview (7)