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DLINFO(3)	       FreeBSD Library Functions Manual		     DLINFO(3)

NAME
     dlinfo -- information about dynamically loaded object

LIBRARY
     Standard C	Library	(libc, -lc)

SYNOPSIS
     #include <link.h>
     #include <dlfcn.h>

     int
     dlinfo(void * restrict handle, int	request, void *	restrict p);

DESCRIPTION
     The dlinfo() function provides information	about dynamically loaded
     object.  The action taken by dlinfo() and exact meaning and type of p
     argument depend on	value of the request argument provided by caller.

     The handle	argument is either the value returned from the dlopen(3) func-
     tion call or special handle RTLD_SELF.  If	handle is the value returned
     from dlopen(3), the information returned by the dlinfo() function per-
     tains to the specified object.  If	handle is the special handle
     RTLD_SELF,	the information	returned pertains to the caller	itself.

     Possible values for the request argument are:

     RTLD_DI_LINKMAP
	     Retrieve the Link_map (struct link_map) structure pointer for the
	     specified handle.	On successful return, the p argument is	filled
	     with the pointer to the Link_map structure	(Link_map **p)
	     describing	a shared object	specified by the handle	argument.  The
	     Link_map structures are maintained	as a doubly linked list	by
	     ld.so(1), in the same order as dlopen(3) and dlclose(3) are
	     called.  See EXAMPLES, example 1.

	     The Link_map structure is defined in <link.h> and has the follow-
	     ing members:

		   caddr_t	   l_addr;    /* Base Address of library */
		   const char	   *l_name;   /* Absolute Path to Library */
		   const void	   *l_ld;     /* Pointer to .dynamic in	memory */
		   struct link_map *l_next,   /* linked	list of	mapped libs */
				   *l_prev;

	     l_addr  The base address of the object loaded into	memory.

	     l_name  The full name of the loaded shared	object.

	     l_ld    The address of the	dynamic	linking	information segment
		     (PT_DYNAMIC) loaded into memory.

	     l_next  The next Link_map structure on the	link-map list.

	     l_prev  The previous Link_map structure on	the link-map list.

     RTLD_DI_SERINFO
	     Retrieve the library search paths associated with the given
	     handle argument.  The p argument should point to Dl_serinfo
	     structure buffer (Dl_serinfo *p).	The Dl_serinfo structure must
	     be	initialized first with the RTLD_DI_SERINFOSIZE request.

	     The returned Dl_serinfo structure contains	dls_cnt	Dl_serpath
	     entries.  Each entry's dlp_name field points to the search	path.
	     The corresponding dlp_info	field contains one of more flags indi-
	     cating the	origin of the path (see	the LA_SER_* flags defined in
	     the <link.h> header file).	 See EXAMPLES, example 2, for a	usage
	     example.

     RTLD_DI_SERINFOSIZE
	     Initialize	a Dl_serinfo structure for use in a RTLD_DI_SERINFO
	     request.  Both the	dls_cnt	and dls_size fields are	returned to
	     indicate the number of search paths applicable to the handle, and
	     the total size of a Dl_serinfo buffer required to hold dls_cnt
	     Dl_serpath	entries	and the	associated search path strings.	 See
	     EXAMPLES, example 2, for a	usage example.

     RTLD_DI_ORIGIN
	     Retrieve the origin of the	dynamic	object associated with the
	     handle.  On successful return, p argument is filled with the char
	     pointer (char *p).

RETURN VALUES
     The dlinfo() function returns 0 on	success, or -1 if an error occurred.
     Whenever an error has been	detected, a message detailing it can be
     retrieved via a call to dlerror(3).

EXAMPLES
     Example 1:	Using dlinfo() to retrieve Link_map structure.

     The following example shows how dynamic library can detect	the list of
     shared libraries loaded after caller's one.  For simplicity, error	check-
     ing has been omitted.

	   Link_map *map;

	   dlinfo(RTLD_SELF, RTLD_DI_LINKMAP, &map);

	   while (map != NULL) {
		   printf("%p: %s\n", map->l_addr, map->l_name);
		   map = map->l_next;
	   }

     Example 2:	Using dlinfo() to retrieve the library search paths.

     The following example shows how a dynamic object can inspect the library
     search paths that would be	used to	locate a simple	filename with
     dlopen(3).	 For simplicity, error checking	has been omitted.

	   Dl_serinfo	    _info, *info = &_info;
	   Dl_serpath	   *path;
	   unsigned int	    cnt;

	   /* determine	search path count and required buffer size */
	   dlinfo(RTLD_SELF, RTLD_DI_SERINFOSIZE, (void	*)info);

	   /* allocate new buffer and initialize */
	   info	= malloc(_info.dls_size);
	   info->dls_size = _info.dls_size;
	   info->dls_cnt = _info.dls_cnt;

	   /* obtain sarch path	information */
	   dlinfo(RTLD_SELF, RTLD_DI_SERINFO, (void *)info);

	   path	= &info->dls_serpath[0];

	   for (cnt = 1; cnt <=	info->dls_cnt; cnt++, path++) {
		   (void) printf("%2d: %s\n", cnt, path->dls_name);
	   }

SEE ALSO
     rtld(1), dladdr(3), dlopen(3), dlsym(3)

HISTORY
     The dlinfo() function first appeared in the Solaris operating system.  In
     FreeBSD, it first appeared	in FreeBSD 4.8.

AUTHORS
     The FreeBSD implementation	of the dlinfo()	function was originally	writ-
     ten by Alexey Zelkin <phantom@FreeBSD.org>	and later extended and
     improved by Alexander Kabaev <kan@FreeBSD.org>.

     The manual	page for this function was written by Alexey Zelkin
     <phantom@FreeBSD.org>.

FreeBSD	9.3		       February	14, 2003		   FreeBSD 9.3

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | SEE ALSO | HISTORY | AUTHORS

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