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

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

DESCRIPTION
     ld-elf.so.1 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.

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

     ld-elf.so.1 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_LIBMAP_DISABLE
                      If set, disables the use of libmap.conf(5).
                      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_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

     /etc/libmap.conf
             The libmap configuration file.

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

FreeBSD 4.10                   January 28, 2000                   FreeBSD 4.10

NAME | DESCRIPTION | FILES | SEE ALSO

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