File: dlopen.3

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.\" -*- nroff -*-
.\" Copyright 1995 Yggdrasil Computing, Incorporated.
.\" written by Adam J. Richter (adam@yggdrasil.com),
.\" with typesetting help from Daniel Quinlan (quinlan@yggdrasil.com).
.\"
.\" This is free documentation; you can redistribute it and/or
.\" modify it under the terms of the GNU General Public License as
.\" published by the Free Software Foundation; either version 2 of
.\" the License, or (at your option) any later version.
.\"
.\" The GNU General Public License's references to "object code"
.\" and "executables" are to be interpreted as the output of any
.\" document formatting or typesetting system, including
.\" intermediate and printed output.
.\"
.\" This manual is distributed in the hope that it will be useful,
.\" but WITHOUT ANY WARRANTY; without even the implied warranty of
.\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
.\" GNU General Public License for more details.
.\"
.\" You should have received a copy of the GNU General Public
.\" License along with this manual; if not, write to the Free
.\" Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
.\" USA.
.\"
.\" Modified by David A. Wheeler <dwheeler@dwheeler.com> 2000-11-28.
.\" Applied patch by Terran Melconian, aeb, 2001-12-14
.\"
.\" Japanese Version Copyright (c) 1998 NAKANO Takeo all rights reserved.
.\" Translated Sat May 23 1998 by NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\" Updated & Modified Tue Sep 14 1999 by NAKANO Takeo 
.\"
.\" Modified Sun Mar 19 23:01:38 JST 2000
.\"         by HANATAKA Shinya <hanataka@abyss.rim.or.jp>
.\" Updated Fri Feb 16 JST 2001 by Kentaro Shirakata <argrath@ub32.org>
.\" Updated Fri Dec 21 JST 2001 by Kentaro Shirakata <argrath@ub32.org>
.\"
.TH DLOPEN 3 2001-12-14 "Linux" "Linux Programmer's Manual"
.SH ̾
dlclose, dlerror, dlopen, dlsym \- ʥߥå󥯤ԤؤΥץߥ󥰥󥿡ե
.SH 
.B #include <dlfcn.h>
.sp
.BI "void *dlopen(const char *" filename ", int " flag );
.br
.BI "const char *dlerror(void);"
.br
.BI "void *dlsym(void *" handle ", char *" symbol );
.br
.BI "int dlclose(void *" handle );
.sp
üʥܥ:
.BR "_init" ", " "_fini"
.SH 
.B dlopen
 NUL üʸ
.I filename
ǻꤵ줿̾Υեʥߥå饤֥Ȥƥɤ
Υʥߥå饤֥
Ʃ (opaque) ʡ֥ϥɥפ֤
.\"?? opaque ϥɥ?
.I filename
Хѥ ("/" ǻϤޤѥ) \fIʤ\fPˤϡե
ʲξ꤫鸡롣
.RS
.PP
桼 \fBLD_LIBRARY_PATH\fP Ķѿǻꤵ줿ڤ
ǥ쥯ȥꥹȡ
.PP
\fI/etc/ld.so.cache\fP ˤ饤֥ꡦåΥꥹȡ
.PP
\fI/usr/lib\fP  \fI/lib\fP
.RE
.PP
.I filename
 NULL ݥ󥿤Ǥϡ
֤ϥɥϥᥤץΤΤˤʤ롣
.PP
ץ󤵤줿饤֥ǤγȤϡ
Υ饤֥ΰ¸ꥹȤˤ饤֥꤫Ǥ
.B RTLD_GLOBAL
ե饰ȶ˥ץ󤵤Ƥ饤֥ѤƲ褵롣
¹ԥե뤬 "-rdynamic" ե饰ȤȤ˥󥯤Ƥϡ
¹ԥեΥХ륷ܥ⡢
ʥߥå˥ɤ饤֥ؤλȲѤ롣
.PP
.I flag
ϰʲΤ줫ǤʤФʤʤ:
.B RTLD_LAZY
ϥʥߥå饤֥Υɤ¹Ԥݤ
̤ܥ缡褷ƤȤ򼨤
.B RTLD_NOW

.B dlopen
νκǸǤ٤Ƥ̤ܥ褷줬Ǥʤˤ 
dlopen ԤȤʤ뤳Ȥ򼨤
.B RTLD_GLOBAL

.I flag
 OR 黻뤳ȤǤ롣ξˤϡ饤֥Ƥ
ܥ뤬³ƥɤ¾Υ饤֥Ǥͭˤʤ롣
.PP
饤֥꤬
.B _init
Ȥ̾Υ롼򥨥ݡȤƤС dlopen λˤ
Υɤ¹Ԥ롣Ʊ饤֥꤬
.B dlopen()
ˤä٥ɤ줿ˤϡƱեϥɥ뤬֤롣
dl 饤֥ϥʥߥåեϥɥΥ󥯿ݻƤ롣
äƥʥߥå饤֥
.B dlclose

.B dlopen
ƱƤӽФʤХɤʤ
.PP
.B dlopen
ϡ餫ͳǼԤ NULL ֤
dl 롼 (dlopen, dlsym, dlclose) Τ줫
Ǥᤤ顼ϡ
.B dlerror()
ˤäƿʹ֤˲ɤʷɽ뤳ȤǤ롣
.B dlerror
Ͻ줿뤤ϺǸ˸ƤӽФ줿饨顼ä
ʤ NULL ֤ (
.B dlerror()
 2 ³ƸƤӽФȡ 2 ܤΥǤɬ NULL ֤롣)
.PP
.B dlsym
 dlopen ˤä֤줿ʥߥå饤֥Ρ֥ϥɥפȡ 
̥ʸǽü줿ʸΥܥ̾˼ꡢ
Υܥ뤬ɤƤ륢ɥ쥹֤
ܥ뤬Ĥʤˤϡ
.B dlsym
 NULL ֤
.B dlsym
Υ顼Ĵ٤ˤϡ
.B dlerror
η̤ѿ¸
줬 NULL ǤʤɤåΤǤ롣
ܥͤºݤ NULL Ǥ⤢뤫Ǥ롣ޤ
.B dlerror
η̤ѿ¸ƤȤɬפʤȤǤ롣ʤʤ⤦
.B dlerror
ƤӽФȡ֤ͤ NULL ȤʤäƤޤǤ롣
.PP
.B RTLD_DEFAULT

.B RTLD_NEXT
ȤĤ̤ʵϥɥ뤬롣
ԤϥǥեȤΥ饤֥긡Ȥäơ륷ܥ뤬
ǽ˸Ȥõ
Ԥ(ʥߥå饤֥ǤΤͭѤǤ뤬)
ǸߤΥ饤֥ʹߡ˴ؿȤõ
ˤꡢ¾ζͭ饤֥δؿؤΥåѡ󶡤Ǥ롣
.PP
.B dlclose
ϥʥߥå饤֥Υϥɥ
.I handle
λȥȤ 1 餹ȥȤ 0 ˤʤꡢ¾
ɤƤ饤֥ˤäƥܥ뤬ȤƤʤС
Υʥߥå饤֥ϥɤ롣
Υʥߥå饤֥ˤä
.B _fini
Ȥ̾Υ롼󤬥ݡȤƤˤϡ
饤֥򥢥ɤľˤΥ롼󤬸ƤӽФ롣
.SH ֤
.B dlclose
 0 ֤顼λ 0 ֤
.SH 
.B math 饤֥ɤ2.0 ;ɽ롣
.RS
.nf
.if t .ft CW
#include <stdio.h>
#include <dlfcn.h>

int main(int argc, char **argv) {
    void *handle;
    double (*cosine)(double);
    char *error;

    handle = dlopen ("/lib/libm.so", RTLD_LAZY);
    if (!handle) {
        fputs (dlerror(), stderr);
        exit(1);
    }

    cosine = dlsym(handle, "cos");
    if ((error = dlerror()) != NULL)  {
        fprintf (stderr, "%s\en", error);
        exit(1);
    }

    printf ("%f\en", (*cosine)(2.0));
    dlclose(handle);
}
.if t .ft P
.fi
.RE
.PP
Υץ "foo.c" ˽񤤤ȤȡʲΥޥɤǥץ
ӥɤ뤳ȤǤ롣
.RS
.LP
gcc -rdynamic -o foo foo.c -ldl
.RE
.SH ռ
dlopen 󥿡եɸ Solaris ȤˤƤ롣
Linux  dlopen μϡ Eric Youngdale ˤäƤʤ줿
ΤȤ Mitch D'Souza, David Engel, Hongjiu Lu, Andreas Schwab 
Ϥä
Υޥ˥奢ڡ Adam Richter 񤤤
.SH Ϣ
.BR ld (1),
.BR ld.so (8),
.BR ldconfig (8),
.BR ldd (1),
.B ld.so.info