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RTLD(1)			FreeBSD	General	Commands Manual		       RTLD(1)

NAME
     ld-elf.so.1, rtld -- run-time link-editor

DESCRIPTION
     The ld-elf.so.1 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
     determine which shared libraries are needed and loads them	using the
     mmap(2) system call.

     After all shared libraries	have been successfully loaded, ld-elf.so.1
     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
     begins.  This is useful for C++ libraries that contain static construc-
     tors.

     The ld-elf.so.1 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, ld-elf.so.1 may
     use a ``hints'' file prepared by the ldconfig(8) utility.

     The ld-elf.so.1 utility recognizes	a number of environment	variables that
     can be used to modify its behaviour as follows:

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

     LD_BIND_NOW      When set to a nonempty string, causes ld-elf.so.1	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 unexpectedly
		      undefined	functions.

     LD_TRACE_LOADED_OBJECTS
		      When set to a nonempty string, causes ld-elf.so.1	to
		      exit after loading the shared objects and	printing a
		      summary which includes the absolute pathnames of all
		      objects, to standard output.

     LD_TRACE_LOADED_OBJECTS_ALL
		      When set to a nonempty string, causes ld-elf.so.1	to
		      expand the summary to indicate which objects caused each
		      object to	be loaded.

     LD_TRACE_LOADED_OBJECTS_FMT1

     LD_TRACE_LOADED_OBJECTS_FMT2
		      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
			    ``__progname'').

		      %A    The	value of the environment variable
			    LD_TRACE_LOADED_OBJECTS_PROGNAME

		      %o    The	library	name.

		      %m    The	library's major	version	number.

		      %p    The	full pathname as determined by rtld's library
			    search rules.

		      %x    The	library's load address.

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

FILES
     /var/run/ld-elf.so.hints

SEE ALSO
     ld(1), ldd(1), elf(5), ldconfig(8)

FreeBSD	10.1		       January 28, 2000			  FreeBSD 10.1

NAME | DESCRIPTION | FILES | SEE ALSO

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