.\" $NetBSD: dlfcn.3,v 1.3 1996/01/09 19:43:34 pk Exp $ .\" .\" Copyright (c) 1995 Paul Kranenburg .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" 3. All advertising materials mentioning features or use of this software .\" must display the following acknowledgement: .\" This product includes software developed by Paul Kranenburg. .\" 3. The name of the author may not be used to endorse or promote products .\" derived from this software without specific prior written permission .\" .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd September 30, 1995 .Dt DLFCN 3 .Os .Sh NAME .Nm dlopen .Nm dlclose .Nm dlsym .Nm dlctl .Nm dlerror .Nd dynamic link interface .Sh SYNOPSIS .Fd #include <dlfcn.h> .Ft "void *" .Fn dlopen "char *path" "int mode" .Ft "int" .Fn dlclose "void *handle" .Ft "void *" .Fn dlsym "void *handle" "char *symbol" .Ft "int" .Fn dlctl "void *handle" "int cmd" "void *data" .Ft "char *" .Fn dlerror "void" .Sh DESCRIPTION These functions provide an interface to the run-time linker .Xr ld.so . They allow new shared objects to be loaded into the process' address space under program control. The .Fn dlopen function takes a name of a shared object as the first argument. The shared object is mapped into the address space, relocated and its external references are resolved in the same way as is done with the implicitly loaded shared libraries at program startup. The argument can either be an absolute pathname or it can be of the form .Sm off .Do Xo lib Ao name Ac .so .Op .xx Op .yy Xc .Dc .Sm on in which case the same library search rules apply that are used for .Dq intrinsic shared library searches. The second argument has currently no effect, but should be set to .Dv DL_LAZY for future compatibility. .Fn dlopen returns a handle to be used in calls to .Fn dlclose , .Fn dlsym and .Fn dlctl . If the named shared object has already been loaded by a previous call to .Fn dlopen .Pq and not yet unloaded by Fn dlclose , a handle refering to the resident copy is returned. .Pp .Fn dlclose unlinks and removes the object referred to by .Fa handle from the process address space. If multiple calls to .fn dlopen have been done on this object .Po or the object was one loaded at startup time .Pc the object is removed when its reference count drops to zero. .Pp .Fn dlsym looks for a definition of .Fa symbol in the shared object designated by .Fa handle . The symbols address is returned. If the symbol cannot be resolved, .Dv NULL is returned. .Pp .Fn dlctl provides an interface similar to .Xr ioctl 2 to control several aspects of the run-time linker's operation. This interface is .Ud . .Pp .Fn dlerror return a character string representing the most recent error that has occurred while processing one of the other functions described here. .Sh SEE ALSO .Xr ld 1 , .Xr rtld 1 , .Xr link 5 .Sh HISTORY Some of the .Nm dl* functions first appeared in SunOS 4. .Sh BUGS An error that occurs while processing a .Fn dlopen request results in the termination of the program.