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RTLD(1)			  BSD General Commands Manual		       RTLD(1)

NAME,, rtld -- run-time link-editor

     The utility is	a self-contained shared	object providing run-
     time support for loading and link-editing shared objects into a process'
     address space.  It	is also	commonly known as the dynamic linker.  It uses
     the data structures contained within dynamically linked programs to de-
     termine which shared libraries are	needed and loads them using the
     mmap(2) system call.

     After all shared libraries	have been successfully loaded,
     proceeds to resolve external references from both the main	program	and
     all objects loaded.  A mechanism is provided for initialization routines
     to	be called on a per-object basis, giving	a shared object	an opportunity
     to	perform	any extra set-up before	execution of the program proper	be-
     gins.  This is useful for C++ libraries that contain static constructors.

     The utility itself is loaded by the kernel together with any
     dynamically-linked	program	that is	to be executed.	 The kernel transfers
     control to	the dynamic linker.  After the dynamic linker has finished
     loading, relocating, and initializing the program and its required	shared
     objects, it transfers control to the entry	point of the program.

     To	locate the required shared objects in the file system, may
     use a "hints" file	prepared by the	ldconfig(8) utility.

     The utility recognizes	a number of environment	variables that
     can be used to modify its behaviour as follows:

     LD_DUMP_REL_POST	If set will	print a	table containing all
			relocations after symbol binding and relocation.

     LD_DUMP_REL_PRE	If set will	print a	table containing all
			relocations before symbol binding and relocation.

     LD_LIBMAP		A library replacement list in the same format as
			libmap.conf(5).	 For convenience, the characters `='
			and `,'	can be used instead of a space and a newline.
			This variable is parsed	after libmap.conf(5), and will
			override its entries.

     LD_LIBMAP_DISABLE	If set,	disables the use of libmap.conf(5) and

     LD_LIBRARY_PATH	A colon	separated list of directories, overriding the
			default	search path for	shared libraries.  This	is ig-
			nored for set-user-ID and set-group-ID programs.

     LD_PRELOAD		A list of shared libraries, separated by colons	and/or
			white space, to	be linked in before any	other shared
			libraries.  If the directory is	not specified then the
			directories specified by LD_LIBRARY_PATH will be
			searched first followed	by the set of built-in stan-
			dard directories.  This	is ignored for set-user-ID and
			set-group-ID programs.

     LD_BIND_NOW	When set to a nonempty string, causes to
			relocate all external function calls before starting
			execution of the program.  Normally, function calls
			are bound lazily, at the first call of each function.
			LD_BIND_NOW increases the start-up time	of a program,
			but it avoids run-time surprises caused	by unexpect-
			edly undefined functions.

			When set to a nonempty string, causes to
			exit after loading the shared objects and printing a
			summary	which includes the absolute pathnames of all
			objects, to standard output.

			When set to a nonempty string, causes to
			expand the summary to indicate which objects caused
			each object to be loaded.


			When set, these	variables are interpreted as format
			strings	a la printf(3) to customize the	trace output
			and are	used by	ldd(1)'s -f option and allows ldd(1)
			to be operated as a filter more	conveniently.  The
			following conversions can be used:

			%a    The main program's name (also known as

			%A    The value	of the environment variable

			%o    The library name.

			%m    The library's major version number.

			%p    The full pathname	as determined by rtld's	li-
			      brary search rules.

			%x    The library's load address.

			Additionally, `\n' and `\t' are	recognized and have
			their usual meaning.

     /var/run/  Hints file.
     /etc/libmap.conf	       The libmap configuration	file.

     ld(1), ldd(1), elf(5), libmap.conf(5), ldconfig(8)

BSD				 May 31, 2003				   BSD


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