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.\"                 copyright (C) 1995 Michael Shields.
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.\" 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 1993-07-24 by Rik Faith <faith@cs.unc.edu>
.\" Modified 1995-05-18 by Jim Van Zandt <jrv@vanzandt.mv.com>
.\" Sun Feb 11 14:07:00 MET 1996  Martin Schulze  <joey@linux.de>
.\"	* layout slightly modified
.\"
.\" Modified Mon Oct 21 23:05:29 EDT 1996 by Eric S. Raymond <esr@thyrsus.com>
.\" Modified Thu Feb 24 01:41:09 CET 2000 by aeb
.\" Modified Thu Feb  9 22:32:09 CET 2001 by bert hubert <ahu@ds9a.nl>, aeb
.\" Modified Mon Nov 11 14:35:00 PST 2002 by Ben Woodard <ben@zork.net>
.\"
.\" Japanese Version Copyright (c) 1997 HANATAKA Shinya
.\"         all rights reserved.
.\" Translated Sun Feb 23 22:43:33 JST 1997
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Modified Sun Mar 12 16:22:57 JST 2000
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated & Modified Mon Jun  4 01:13:06 JST 2001
.\"         by Yuichi SATO <ysato@h4.dion.ne.jp>
.\" Updated & Modified Sun Jul  1 09:58:38 JST 2001 by Yuichi SATO
.\" Updated & Modifedd Mon Jan 14 07:15:45 JST 2002 by Yuichi SATO
.\" Updated 2002-09-24 Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\" Updated 2003-01-19 Akihiro MOTOKI <amotoki@dd.iij4u.or.jp>
.\"
.\"WORD:	synchronous		Ʊ
.\"WORD:	multiplexing		¿Ų
.\"WORD:	file descriptor		ե뵭һ
.\"WORD:	descriptor		һ
.\"WORD:	macro			ޥ
.\"WORD:	block			(block)
.\"WORD:	block			ػ(block)
.\"WORD:	signal			ʥ
.\"WORD:	timeout			ڤ(timeout)
.\"WORD:	portable		ܿΤ
.\"
.TH SELECT 2 2001-02-09 "Linux 2.4" "Linux Programmer's Manual"
.SH ̾
select, pselect, FD_CLR, FD_ISSET, FD_SET, FD_ZERO \- ¿Ų줿 I/O ƱȤ
.SH 
/* POSIX 1003.1-2001 ˽ */
.br
.B #include <sys/select.h>
.sp
/* εʤ˽ */
.br
.B #include <sys/time.h>
.br
.B #include <sys/types.h>
.br
.B #include <unistd.h>
.sp
\fBint select(int \fIn\fB, fd_set *\fIreadfds\fB,
fd_set *\fIwritefds\fB, fd_set *\fIexceptfds\fB,
struct timeval *\fItimeout\fB);
.sp
\fBint pselect(int \fIn\fB, fd_set *\fIreadfds\fB,
fd_set *\fIwritefds\fB, fd_set *\fIexceptfds\fB,
const struct timespec *\fItimeout\fB, const sigset_t *\fIsigmask\fB);
.sp
.BI "FD_CLR(int " fd ", fd_set *" set );
.br
.BI "FD_ISSET(int " fd ", fd_set *" set );
.br
.BI "FD_SET(int " fd ", fd_set *" set );
.br
.BI "FD_ZERO(fd_set *" set );
.fi
.SH 
.B select

.B pselect
ξؿϡʣΥե뵭һ (file descriptor) ƻ뤷
ξ֤ѲΤԤġ
.PP
2 ĤδؿεǽƱǤ뤬ʲ 3 ۤʤ:
.TP
(i)
.B select
ؿϡॢȻ֤λ˹¤
.I struct timeval
(áޥñ)Ѥ롣

.B pselect
ؿǤϡ¤
.I struct timespec
(áʥñ)Ѥ롣
.TP
(ii)
.B select
ؿϡĤ֤򼨤
.I timeout
ѥ᡼򹹿뤳Ȥ롣
.B pselect
ؿϡΥѥ᡼ѹʤ
.TP
(iii)
.B select
ؿ
.I sigmask
ѥ᡼
.I sigmask
 NULL ꤷ
.B pselect
Ʊư򤹤롣
.PP
3 ĤΩһҽδƻԤ
.I readfds
˥ꥹȤ줿ΤˤĤƤϡɤ߹ߤǽɤƻ뤹
(Τˤȡ (block) ʤɤळȤǤ뤫Ĵ٤롣
ե뵭һҤեνü (end-of-file) 
ɤ߹߲ǽ˴ޤޤ)
.I writefds
˥ꥹȤ줿ΤˤĤƤϡߤ˽񤭹ߤǽɤƻ뤹롣
.I exceptfds
ˤΤˤĤƤϡ㳰δƻԤʤλˡºݤˤɤ
һҤξ֤ѲˡƤѹ롣
.PP
뤿 4 ĤΥޥ (macro) 󶡤Ƥ롣
.B FD_ZERO
Ͻõ (clear) 롣
.B FD_SET

.B FD_CLR
Ͻ˵һҤɲäꤹ롣
.B FD_ISSET
Ͻ˵һҤ뤫ɤĴ٤; 
.B select
λ˻ȤǤ롣
.PP
.I n
 3 Ĥνˤ뵭һҤκͤ 1 ­ΤǤ롣
.PP
.I timeout

.B select
֤äƤޤǤηв֤ξ¤Ǥ롣 0 ˤ뤳ȤǤ
ξ
.B select
Ϥ֤äƤ롣
(ˡϥݡ (polling) ԤΤǤ롣)
.I timeout
 NULL (ॢȤʤ)
ꤵȡ
.B select
̵¤ (block) 롣
.PP
.I sigmask
ϡʥޥ
.RB ( sigprocmask (2)
򻲾) ؤΥݥ󥿤Ǥ롣
.I sigmask
 NULL Ǥʤ硢
.B pselect

.I sigmask
ؤƤ륷ʥޥǸߤΥʥޥ֤Ƥ顢
`select' ؿ¹Ԥ
λ˥ʥޥ򸵤Υʥޥ᤹
.PP
ֲ餫Υ٥
(ʥե뵭һҤξѲ) ԤȤˤϡ
֤򤱤뤿 atomic ʥƥȤɬפˤʤפȤΤ
.B pselect
ιͤǤ롣
(ʥϥɥ餬ե饰ꤷΤȤ롣
ΤȤե饰ΥƥȤ³
.BR select ()
ƤӽФȡ
ʥ뤬ƥȤľ夫ĸƤӽФľϤ
.BR select ()
ϱʵפ˥ϥ󥰤Ƥޤ⤷ʤ

.B pselect
Ȥȡޤʥػ (block) ơäƤ륷ʥ
˾ߤ
.I sigmask

.BR pselect ()
ƤӽФȤǡ򤱤뤳ȤǤ롣)
Ԥ Linux ˤ
.IR pselect ()
ƥॳ뤬ʤΤǡ
ߤ glibc2 롼ˤϤζ礬ǽޤޤޤˤʤäƤ롣
.SS ॢ
δؿ˴ޤޤִϢι¤Τϡ
.I <sys/time.h>
ƤꡢΤ褦ˤʤäƤ롣

.RS
.nf
struct timeval { 
    long    tv_sec;         /*  */
    long    tv_usec;        /* ޥ */
};
.fi
.RE

.RS
.nf
struct timespec {
    long    tv_sec;         /*  */
    long    tv_nsec;        /* ʥ */
};
.fi
.RE
(âPOSIX 1003.1-2001 ǤˤĤƤϲΡաפ򻲾)
.PP
ñ̰ʲ٤ǥ꡼פ¸
ܿ (portable) ι⤤ˡȤơ
3 ĤνƤ
.I n
 0 
.I timeout
 NULL Ǥʤͤꤷ
.B select
ƤӽФȤˡȤäƤ륳ɤ⤢롣
.PP
Linux Ǥϡ
.B select
ؿ
.I timeout
ѹĤ߻֤ȿǤ褦ˤʤäƤ롣
¾ΤۤȤɤμǤϤΤ褦ˤʤäƤʤ
Τᡢ
.I timeout
򻲾Ȥ Linux Υɤ¾Υڥ졼ƥ󥰡ƥذܿ
ȡ롼פ timeval ¤ΤˤΤޤ޺Ѥ
.B select
ʣԤʤäƤ륳ɤ Linux ذܿˡ꤬롣
.B select
֤äƤ
.I timeout
̤Ǥȹͤ٤Ǥ롣
.\" .PP
.\" BSD ǤϥॢȤäƤ⡢
.\" ե뵭һҥӥåȤѤʤפʹȤ롣
.\" Linux  SUSv2 ˽äƤꡢ
.\" ॢȤκݤˤϥӥåȥޥ 0 ˤפȤΤϳΤ˻¤Ǥ롣
.SH ֤
硢
.B select

.B pselect
ϵһҽ˴ޤޤƤ뵭һҤο֤
ⵯ餺˻ڤˤʤä硢
һҤο 0 ˤʤ뤳Ȥ⤢롣
顼ʤ \-1 ֤
.I errno
Ŭڤͤꤵ; 
.I timeout
̤ȤʤΤǡ顼äϤƤꤷƤϤʤʤ
.SH 顼
.TP
.B EBADF
Τɤ줫̵ʥե뵭һҤͿ줿
.TP
.B EINTR
ػ (block) Ƥʤʥ (signal) 
.TP
.B EINVAL
.I n
顢ޤ
.I timeout
äƤͤǤ롣
.TP
.B ENOMEM
.B select
ơ֥˥Ƥ뤳ȤǤʤä
.SH 
.nf
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>

int
main(void) {
    fd_set rfds;
    struct timeval tv;
    int retval;

    /* stdin (fd 0) ƻ뤷Ϥäɽ롣*/
    FD_ZERO(&rfds);
    FD_SET(0, &rfds);
    /* 5 ôִƻ뤹롣*/
    tv.tv_sec = 5;
    tv.tv_usec = 0;

    retval = select(1, &rfds, NULL, NULL, &tv);
    /* λǤ tv ͤꤷƤϤʤʤ*/

    if (retval == -1)
	perror("select()");
    else if (retval)
        printf("ǡǤޤ\\n");
        /* FD_ISSET(0, &rfds)  true ˤʤ롣*/
    else
        printf("5 ð˥ǡϤޤǤ\\n");

    return 0;
}
.fi
.SH 
4.4BSD
.RB ( select
ؿ 4.2BSD Ǻǽо줷)
BSD åؤΥ򥵥ݡȤƤ BSD ƥ
(System V Ϥޤ) Ȥδ֤Ǥܿ롣 System V ϤǤ
 timeout ѿ exit ˥åȤ뤬
BSD ϤǤϤǤʤΤդ뤳ȡ
.PP
.B pselect
ؿ IEEE Std 1003.1g-2000 (POSIX.1g) 
POSIX 1003.1-2001 ΰƤ롣
δؿ glibc2.1 ʹߤˤ롣
glibc2.0 ˤƱ̾δؿ뤬
.I sigmask
ѥ᡼Ȥʤ
.SH 
fd_set ϸꥵΥХåեǤ롣
 FD_SETSIZE ʾͤ
.I fd
Ф FD_CLR  FD_SET ¹Ԥ硢
ɤΤ褦ư򤹤뤫Ƥʤ
ޤ POSIX Ǥ
.I fd
ͭʥե뵭һҤǤʤФʤʤ

˴ؤơΤʤξǤ timeval ¤Τ 2 ĤΥեɤ
(嵭Τ褦)ξȤ long Ǥꡢ¤Τ
.I <sys/time.h>
Ƥ롣
POSIX 1003.1-2001 βǤϡʲΤ褦ˤʤäƤ롣

.RS
.nf
struct timeval {
	 time_t         tv_sec;     /*  */
	 suseconds_t    tv_usec;    /* ޥ */
};
.fi
.RE

ι¤Τ
.I <sys/select.h>
Ƥꡢǡ time_t  suseconds_t 
.I <sys/types.h>
Ƥ롣
.LP
ץȥפ˴ؤƤϡΤʤξ
.B select
Ȥϡ
.I <time.h>
򥤥󥯥롼ɤФ褤
POSIX 1003.1-2001 δĶ
.B select

.B pselect
Ȥϡ
.I <sys/select.h>
򥤥󥯥롼ɤФ褤
إåե
.I <sys/select.h>
 libc4  libc5 ˤϤʤglibc 2.0 ʹߤ¸ߤ롣
Ȥ glibc 2.0 Ǥ
.B pselect
ΥץȥפְäƤ롣
glibc 2.1-2.2.1 Ǥ
.B _GNU_SOURCE
Ƥˡ
.B pselect
󶡤롣
glibc 2.2.2-2.2.4 Ǥ
.B _XOPEN_SOURCE
Ƥơͤ 600 ʾǤ
.B pselect
󶡤롣
 POSIX 1003.1-2001 ʹߤǤϡǥեȤǥץȥפ󶡤롣
.SH Ϣ
ͻȻν񤫤줿塼ȥꥢȤơ
.BR select_tut (2)
롣
.LP
طꤽʤΤ󤲤Ƥ:
.BR accept (2),
.BR connect (2),
.BR poll (2),
.BR read (2),
.BR recv (2),
.BR send (2),
.BR sigprocmask (2),
.BR write (2)