.\" Hey Emacs! This file is -*- nroff -*- source.
.\"
.\" Copyright (C) 2006 Michael Kerrisk <mtk.manpages@gmail.com>
.\" A few fragments remain from an earlier (1992) page by
.\" Drew Eckhardt (drew@cs.colorado.edu),
.\"
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
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.\" 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.
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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.\" manual page may be incorrect or out-of-date.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
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.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" Modified by Michael Haardt (michael@moria.de)
.\" Modified Sat Jul 24 13:22:07 1993 by Rik Faith (faith@cs.unc.edu)
.\" Modified 21 Aug 1994 by Michael Chastain (mec@shell.portal.com):
.\"   Referenced 'clone(2)'.
.\" Modified 1995-06-10, 1996-04-18, 1999-11-01, 2000-12-24
.\"   by Andries Brouwer (aeb@cwi.nl)
.\" Modified, 27 May 2004, Michael Kerrisk <mtk.manpages@gmail.com>
.\"     Added notes on capability requirements
.\" 2006-09-04, Michael Kerrisk
.\"     Greatly expanded, to describe all attributes that differ
.\"	parent and child.
.\"
.\" Japanese Version Copyright (c) 1996 TABATA Tomohira
.\"         all rights reserved.
.\" Translated Thu Jun 27 20:35:06 JST 1996
.\"         by TABATA Tomohira <loba@k2.t.u-tokyo.ac.jp>
.\" Modified Sun Dec 14 00:43:22 JST 1997
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Modified Tue Jul 10 05:36:22 JST 2001
.\"         by Yuichi SATO <ysato@h4.dion.ne.jp>, LDP v1.38
.\" Updated & Modified Wed Dec 29 12:33:12 JST 2004
.\"         by Yuichi SATO <ysato444@yahoo.co.jp>, LDP v2.01
.\" Updated & Modified Wed Jan  3 04:11:03 JST 2007 by Yuichi SATO, LDP v2.43
.\" Updated 2008-08-04, Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>, LDP v3.05
.\"
.TH FORK 2 2009-02-04 "Linux" "Linux Programmer's Manual"
.SH ̾
fork \- ҥץ
.SH 
.B #include <unistd.h>
.sp
.B pid_t fork(void);
.SH 
.BR fork ()
ϸƤӽФץʣƿץ롣
\fIchild\fP ǻȤ뿷ץϡʲ
\fIparent\fP ǻȤƤӽФץδʣǤ:
.IP * 3
ҥץȼΥץ ID 
 PID ϴ¸ΤɤΥץ롼
.RB ( setpgid (2))
 ID Ȥפʤ
.IP *
ҥץοƥץ ID ϡƥץΥץ ID ƱǤ롣
.IP *
ҥץϿƥץΥå
.RB ( mlock (2),
.BR mlockall (2))
Ѥʤ
.IP *
ץλ
.RB ( getrusage (2))
 CPU ५
.RB ( times (2))
ҥץǤ 0 ˥ꥻåȤ롣
.IP *
ҥץνԤΥʥν
.RB ( sigpending (2))
ϡ֤Ǥ϶ˤʤ롣
.IP *
ҥץϿƥץ饻ޥեĴ
.RB ( semop (2))
Ѥʤ
.IP *
ҥץϿƥץ쥳ɥå
.RB ( fcntl (2))
Ѥʤ
.IP *
ҥץϿƥץ饿ޡ
.RB ( setitimer (2),
.BR alarm (2),
.BR timer_create (2))
Ѥʤ
.IP *
ҥץϿƥץäƱ I/O 
.RB ( aio_read (3),
.BR aio_write (3))
Ѥʤ
.PP
嵭ΥꥹȤˤץ°ϡPOSIX.1-2001 ƻꤵƤ롣
ƥץȻҥץϡʲ Linux ͭΥץ°ۤʤ:
.IP * 3
ҥץϿƥץǥ쥯ȥѹ (dnotify)
.RB ( fcntl (2)
ˤ
.B F_NOTIFY
򻲾) Ѥʤ
.IP *
.BR prctl (2)

.B PR_SET_PDEATHSIG
꤬ꥻåȤ졢ҥץϿƥץλȤ
ʥʤ
.IP *
.BR madvise (2)

.B MADV_DONTFORK
ե饰ǥޡ줿ޥåԥ󥰤ϡ
.BR fork ()
ˤäưѤʤ
.IP *
ҥץνλʥϾ
.B SIGCHLD
Ǥ
.RB ( clone (2)
򻲾)
.PP
˰ʲˤĤդ뤳:
.IP * 3
ҥץϥ󥰥륹åɤ롣Ĥޤꡢ
.BR fork ()
ƤӽФåɤȤʤ롣
ƥץβۥɥ쥹Τҥץʣ롣
ˤϥߥ塼ƥå (mutex) ξ֡ѿ
pthread ֥Ȥޤޤ롣
줬򰷤ˤϡ
.BR pthread_atfork (3)
Ȥɤ
.IP *
ҥץϿƥץ
ץեǥץνΥԡѤ
ҥץγƥեǥץϡ
ƥץΥեǥץб
Ʊץե뵭 (file description) 򻲾Ȥ
.RB ( open (2)
򻲾)
 2 ĤΥǥץե֥ե饰
ߤΥե륪եåȡʥư (signal-driven) I/O °
.RB ( fcntl (2)
ˤ
.BR F_SETOWN ,
.B F_SETSIG
򻲾) ͭ뤳Ȥ̣롣
.IP *
ҥץϿƥץĥץå塼ǥץ
.RB ( mq_overview (7)
򻲾) νΥԡѤ
ҥץγƥǥץϡ
ƥץΥǥץб
Ʊץå塼ǥץ򻲾Ȥ롣
 2 ĤΥǥץƱե饰
.RI ( mq_flags )
ͭ뤳Ȥ̣롣
.IP *
ҥץϡƥץΥץѤߤΥǥ쥯ȥꥹȥ꡼ν
.RB ( opendir (3)
) ΥԡѾ롣
POSIX.1-2001 ǤϡƥץȻҥץ֤бǥ쥯ȥꥹȥ꡼
ϥǥ쥯ȥꥹȥ꡼ΰ (positioning) ͭƤ褤ȤƤ롣
Linux/glibc Ǥϥǥ쥯ȥꥹȥ꡼ΰ֤ζͭϹԤƤʤ
.SH ֤
硢ƥץˤϻҥץ PID ֤졢
ҥץˤ 0 ֤롣
Ԥ硢ƥץ \-1 ֤졢ҥץ줺
.I errno
Ŭڤꤵ롣
.SH 顼
.TP
.B EAGAIN
ƥץΥڡơ֥Υԡ
ҥץΥ¤ɬפʥ
.BR fork ()
Ƥ뤳ȤǤʤä
.TP
.B EAGAIN
ƤӽФ
.B RLIMIT_NPROC
񸻤 (resource limit) ãˡץǤʤä
¤Ķˤϡץ
.B CAP_SYS_ADMIN
ޤ
.B CAP_SYS_RESOURCE
ѥӥƥ (capability) äƤʤƤϤʤʤ
.TP
.B ENOMEM
꤬­ʤˡ
.BR fork ()
ɬפʥͥ빽¤ΤƤ뤳ȤǤʤä
.SH 
SVr4, 4.3BSD, POSIX.1-2001.
.SH 
Linux Ǥϡ
.BR fork ()
 񤭹߻ԡ (copy-on-write)ڡѤƼƤ롣
äơfork ԤȤͣΥǥåȤϡ
ƥץΥڡơ֥ʣ
ҥץȤΥ¤κΤλ֤ȥ꤬ɬפʤȤǤ롣

glibc 2.3.3 ʹߤǤϡ
NPTL åɼΰȤ󶡤Ƥ glibc 
.BR fork ()
åѡؿϡ
ͥ
.BR fork ()
ƥॳưΤǤϤʤ
.BR clone (2)
ư롣
.BR clone (2)
Ϥե饰ȤơŪ
.BR fork ()
ƥॳƱ̤褦ʥե饰ꤵ롣
glibc Υåѡؿ
.BR pthread_atfork (3)
ȤäꤵƤǤդ fork ϥɥư롣
.\" getpid(2) ֤ͤȤǤ褦˲餫νԤ

.SH 
.BR pipe (2)

.BR wait (2)
򻲾ȡ
.SH Ϣ
.BR clone (2),
.BR execve (2),
.BR setrlimit (2),
.BR unshare (2),
.BR vfork (2),
.BR wait (2),
.BR daemon (3),
.BR capabilities (7),
.BR credentials (7)