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.\" Copyright (C) 2001 Andries Brouwer <aeb@cwi.nl>.
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" 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
.\" permission notice identical to this one.
.\"
.\" 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.\" manual page may be incorrect or out-of-date.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) 2001 Yuichi SATO
.\"         all rights reserved.
.\" Translated Sun Nov  4 14:09:45 2001
.\"         by Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\"
.\"WORD:        lockcount       ¥í¥Ã¥¯¿ô
.\"WORD:        owner thread    ½êÍ­¼Ô¥¹¥ì¥Ã¥É
.\"
.TH FLOCKFILE 3  2008-08-29 "" "Linux Programmer's Manual"
.\"O .SH NAME
.\"O flockfile, ftrylockfile, funlockfile \- lock FILE for stdio
.SH ̾Á°
flockfile, ftrylockfile, funlockfile \- ɸ½àÆþ½ÐÎÏ FILE ¤Î¥í¥Ã¥¯¤ò¹Ô¤¦
.\"O .SH SYNOPSIS
.SH ½ñ¼°
.nf
.B #include <stdio.h>
.sp
.BI "void flockfile(FILE *" filehandle );
.br
.BI "int ftrylockfile(FILE *" filehandle );
.br
.BI "void funlockfile(FILE *" filehandle );
.fi
.sp
.in -4n
.\"O Feature Test Macro Requirements for glibc (see
.\"O .BR feature_test_macros (7)):
glibc ¸þ¤±¤Îµ¡Ç½¸¡ºº¥Þ¥¯¥í¤ÎÍ×·ï
.RB ( feature_test_macros (7)
»²¾È):
.in
.ad l
.sp
.\"O All functions shown above:
¾åµ­¤ÎÁ´¤Æ¤Î´Ø¿ô:
_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
_SVID_SOURCE || _POSIX_SOURCE
.ad b
.\"O .SH DESCRIPTION
.SH ÀâÌÀ
.\"O The stdio functions are thread-safe.
.\"O This is achieved by assigning
.\"O to each
.\"O .I FILE
.\"O object a lockcount and (if the lockcount is nonzero)
.\"O an owning thread.
ɸ½àÆþ½ÐÎÏ´Ø¿ô¤Ï¥¹¥ì¥Ã¥É¥»¡¼¥Õ¤Ç¤¢¤ë¡£¤³¤ì¤Ï¡¢³Æ
.I FILE
¥ª¥Ö¥¸¥§¥¯¥È¤ËÂФ·¡¢¥í¥Ã¥¯¿ô (lockcount) ¤È
(¥í¥Ã¥¯¿ô¤¬ 0 ¤Ç¤Ê¤¤¾ì¹ç¤Ï) ½êÍ­¼Ô¥¹¥ì¥Ã¥É (owner thread)
¤ò´ÉÍý¤¹¤ë¤³¤È¤Ç¼Â¸½¤µ¤ì¤ë¡£
.\"O For each library call, these functions wait until the
.\"O .I FILE
.\"O object
.\"O is no longer locked by a different thread, then lock it, do the
.\"O requested I/O, and unlock the object again.
¥é¥¤¥Ö¥é¥ê¤Î¸Æ¤Ó½Ð¤·¤¬¹Ô¤ï¤ì¤ëËè¤Ë¡¢É¸½àÆþ½ÐÎÏ´Ø¿ô¤Ï
.I FILE
¥ª¥Ö¥¸¥§¥¯¥È¤¬Â¾¤Î¥¹¥ì¥Ã¥É¤Ë¤è¤Ã¤Æ¥í¥Ã¥¯¤µ¤ì¤Æ¤¤¤Ê¤¤¾õÂ֤ˤʤë¤Þ¤ÇÂÔ¤Á¡¢
.I FILE
¥ª¥Ö¥¸¥§¥¯¥È¤ò¥í¥Ã¥¯¤·¡¢Í׵ᤵ¤ì¤ÆÆþ½ÐÎϤò¹Ô¤¤¡¢
¥ª¥Ö¥¸¥§¥¯¥È¤Î¥í¥Ã¥¯¤ò²ò½ü¤¹¤ë¡£
.LP
.\"O (Note: this locking has nothing to do with the file locking done
.\"O by functions like
.\"O .BR flock (2)
.\"O and
.\"O .BR lockf (3).)
(Ãí: ¤³¤Î¥í¥Ã¥¯¤Ï¡¢
.BR flock (2)
¤ä
.BR lockf (3)
¤È¤¤¤Ã¤¿´Ø¿ô¤¬¹Ô¤¦¥í¥Ã¥¯¤È¤ÏÁ´¤¯Ìµ´Ø·¸¤Ç¤¢¤ë¡£)
.LP
.\"O All this is invisible to the C-programmer, but there may be two
.\"O reasons to wish for more detailed control.
.\"O On the one hand, maybe
.\"O a series of I/O actions by one thread belongs together, and should
.\"O not be interrupted by the I/O of some other thread.
.\"O On the other hand, maybe the locking overhead should be avoided
.\"O for greater efficiency.
¤³¤ì¤é¤Î¤³¤È¤Ï¤¹¤Ù¤Æ C ¥×¥í¥°¥é¥Þ¤Ë¤Ï¸«¤¨¤Ê¤¤Éôʬ¤Ç¹Ô¤ï¤ì¤ë¤¬¡¢
¤è¤êºÙ¤«¤¤À©¸æ¤¬¤Ç¤­¤¿Êý¤¬¤è¤¤Íýͳ¤¬2¤Ä¤¢¤ë¤À¤í¤¦¡£°ì¤Ä¤Ï¡¢°ì¤Ä¤Î¥¹¥ì¥Ã¥É¤¬
¹Ô¤¦°ìÏ¢¤ÎÆþ½ÐÎÏÆ°ºî¤Ï°ì½ï¤Ë¹Ô¤ï¤ì¡¢Â¾¤Î¥¹¥ì¥Ã¥É¤ÎÆþ½ÐÎϤˤè¤Ã¤ÆÃæÃǤµ¤ì¤Ê¤¤
Êý¤¬¤è¤¤¤È¤¤¤¦¤³¤È¤Ç¤¢¤í¤¦¡£¤â¤¦°ì¤Ä¤Ï¡¢¸úΨ¤òÂ礭¤¯¾å¤²¤ë¤¿¤á¤Ë¤Ï
¥í¥Ã¥¯¤Î¥ª¡¼¥Ð¥Ø¥Ã¥É¤òÈò¤±¤ëɬÍפ¬¤¢¤ë¤È¤¤¤¦¤³¤È¤Ç¤¢¤í¤¦¡£
.LP
.\"O To this end, a thread can explicitly lock the
.\"O .I FILE
.\"O object,
.\"O then do its series of I/O actions, then unlock.
.\"O This prevents
.\"O other threads from coming in between.
.\"O If the reason for doing
.\"O this was to achieve greater efficiency, one does the I/O with
.\"O the nonlocking versions of the stdio functions: with
.\"O .BR getc_unlocked (3)
.\"O and
.\"O .BR putc_unlocked (3)
.\"O instead of
.\"O .BR getc (3)
.\"O and
.\"O .BR putc (3).
¤³¤ÎÌÜŪ¤ò¼Â¸½¤¹¤ë¤¿¤á¤Ë¡¢
.I FILE
¥ª¥Ö¥¸¥§¥¯¥È¤Î¥í¥Ã¥¯¡¢°ìÏ¢¤ÎÆþ½ÐÎÏÆ°ºî¤Î¼Â¹Ô¡¢
¥í¥Ã¥¯¤Î²ò½ü¤ò¥¹¥ì¥Ã¥É¤¬ÌÀ¼¨Åª¤Ë»Ø¼¨¤¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
¤³¤ì¤Ë¤è¤ê¡¢Â¾¤Î¥¹¥ì¥Ã¥É¤¬ÅÓÃæ¤ÇÆþ½ÐÎϤò¹Ô¤¦¤Î¤òËɻߤ¹¤ë¡£
¤³¤Î¤è¤¦¤Ê¤³¤È¤ò¹Ô¤¦Íýͳ¤¬¸úΨ¤Î¸þ¾å¤Ç¤¢¤ë¤Ê¤é¤Ð¡¢
¥í¥Ã¥¯¤ò¹Ô¤ï¤Ê¤¤¥Ð¡¼¥¸¥ç¥ó¤Îɸ½àÆþ½ÐÎÏ´Ø¿ô¤ò»È¤¦¤³¤È¤â¤Ç¤­¤ë¡£
Î㤨¤Ð¡¢
.BR getc (3)
¤ä
.BR putc (3)
¤ÎÂå¤ï¤ê¤Ë
.BR getc_unlocked (3)
¤ä
.BR putc_unlocked (3)
¤ò»ÈÍѤ¹¤ë¡£
.LP
.\"O The
.\"O .BR flockfile ()
.\"O function waits for \fI*filehandle\fP to be
.\"O no longer locked by a different thread, then makes the
.\"O current thread owner of \fI*filehandle\fP, and increments
.\"O the lockcount.
.BR flockfile ()
´Ø¿ô¤Ï¡¢\fI*filehandle\fP ¤¬Â¾¤Î¥¹¥ì¥Ã¥É¤Ë¥í¥Ã¥¯¤µ¤ì¤Æ¤¤¤Ê
¤¤¾õÂ֤ˤʤë¤Þ¤ÇÂԤ俤ΤÁ¡¢¸½ºß¤Î¥¹¥ì¥Ã¥É¤ò \fI*filehandle\fP ¤Î¥ª¡¼¥Ê¤ËÀß
Äꤷ¡¢¥í¥Ã¥¯¿ô¤ò²Ã»»¤¹¤ë¡£
.LP
.\"O The
.\"O .BR funlockfile ()
.\"O function decrements the lock count.
.BR funlockfile ()
´Ø¿ô¤Ï¡¢¥í¥Ã¥¯¿ô¤ò¸º»»¤¹¤ë¡£
.LP
.\"O The
.\"O .BR ftrylockfile ()
.\"O function is a nonblocking version
.\"O of
.\"O .BR flockfile ().
.\"O It does nothing in case some other thread
.\"O owns \fI*filehandle\fP, and it obtains ownership and increments
.\"O the lockcount otherwise.
.BR ftrylockfile ()
´Ø¿ô¤Ï
.BR flockfile ()
¤Î¥Ö¥í¥Ã¥­¥ó¥°¤ò¹Ô¤ï¤Ê¤¤
¥Ð¡¼¥¸¥ç¥ó¤Ç¤¢¤ë¡£Â¾¤Î¥¹¥ì¥Ã¥É¤¬ \fI*filehandle\fP ¤ò¥í¥Ã¥¯¤·¤Æ¤¤¤ë»þ¤Ï
²¿¤â¹Ô¤ï¤º¡¢¤½¤¦¤Ç¤Ê¤¤¾ì¹ç¤Ï \fI*filehandle\fP ¤Î½êÍ­¸¢¤ò³ÍÆÀ¤·¡¢
¥í¥Ã¥¯¿ô¤ò²Ã»»¤¹¤ë¡£
.\"O .SH "RETURN VALUE"
.SH ÊÖ¤êÃÍ
.\"O The
.\"O .BR ftrylockfile ()
.\"O function returns zero for success
.\"O (the lock was obtained), and nonzero for failure.
.BR ftrylockfile ()
´Ø¿ô¤Ï¥í¥Ã¥¯¤ËÀ®¸ù¤¹¤ë¤È 0 ¤òÊÖ¤·¡¢
¼ºÇÔ¤·¤¿¾ì¹ç¤Ï 0 °Ê³°¤ÎÃͤòÊÖ¤¹¡£
.\"O .SH ERRORS
.\"O None.
.SH ¥¨¥é¡¼
¤Ê¤·¡£
.\"O .SH "CONFORMING TO"
.SH ½àµò
POSIX.1-2001.
.\"O .SH AVAILABILITY
.SH ²ÄÍÑÀ­
.\"O These functions are available when
.\"O .B _POSIX_THREAD_SAFE_FUNCTIONS
.\"O is defined.
.\"O They are in libc since libc 5.1.1 and in glibc
.\"O since glibc 2.0.
.B _POSIX_THREAD_SAFE_FUNCTIONS
¤¬ÄêµÁ¤µ¤ì¤Æ¤¤¤ë¤È¤­¤Ë¤³¤ì¤é¤Î´Ø¿ô¤ò»ÈÍѤ¹¤ë¤³¤È¤¬¤Ç¤­¤ë¡£
5.1.1 °Ê¹ß¤Î libc ¤È 2.0 °Ê¹ß¤Î glibc ¤Ë¸ºß¤¹¤ë¡£
.\"O .SH "SEE ALSO"
.SH ´ØÏ¢¹àÌÜ
.BR unlocked_stdio (3)