ld.so(o)                                                 ld.so(o)



NAME
       ld.so/ld-linux.so - dynamic linker/loader

DESCRIPTION
       ld.so loads the shared libraries needed by a program, pre-
       pares the program  to  run,  and  then  runs  it.   Unless
       explicitly  specified  via the -static option to ld during
       compilation, all Linux programs are incomplete and require
       further linking at run time.

       The  necessary  shared libraries needed by the program are
       searched for in the following order

       o      Using  the  environment  variable   LD_LIBRARY_PATH
              (LD_AOUT_LIBRARY_PATH  for a.out programs).  Except
              if the executable is  a  setuid/setgid  binary,  in
              which case it is ignored.

       o      From the cache file /etc/ld.so.cache which contains
              a compiled list of candidate  libraries  previously
              found in the augmented library path.

       o      In the default path /usr/lib, and then /lib.

ENVIRONMENT
       LD_LIBRARY_PATH
              A  colon-separated  list of directories in which to
              search for ELF libraries at execution-time.   Simi-
              lar to the PATH environment variable.

       LD_PRELOAD
              A  whitespace-separated  list  of additional, user-
              specified, ELF shared libraries to be loaded before
              all  others.  This can be used to selectively over-
              ride functions  in  other  shared  libraries.   For
              setuid/setgid  ELF  binaries, only libraries in the
              standard search directories that  are  also  setgid
              will be loaded.

       LD_TRACE_LOADED_OBJECTS
              If  present, causes the program to list its dynamic
              library dependencies, as if run by ldd, instead  of
              running normally.

       LD_BIND_NOW
              If  present,  causes  the dynamic linker to resolve
              all symbols at program startup instead of when they
              are first referenced.

       LD_AOUT_LIBRARY_PATH
              A  colon-separated  list of directories in which to
              search for a.out libraries at execution-time.  Sim-
              ilar to the PATH environment variable.

       LD_AOUT_PRELOAD
              The  name  of  an additional, user-specified, a.out
              shared library to be loaded after all others.  This
              can  be  used  to selectively override functions in
              other shared libraries.

       LD_NOWARN
              Suppress  warnings  about  a.out   libraries   with
              incompatible minor version numbers.

       LD_KEEPDIR
              Don't  ignore  the  directory in the names of a.out
              libraries to be loaded.   Use  of  this  option  is
              strongly discouraged.

FILES
       /lib/ld.so          a.out dynamic linker/loader
       /lib/ld-linux.so.*  ELF dynamic linker/loader
       /etc/ld.so.cache    File  containing  a  compiled  list of
                           directories in  which  to  search  for
                           libraries  and an ordered list of can-
                           didate libraries.
       /etc/ld.so.preload  File containing a whitespace separated
                           list  of  ELF  shared  libraries to be
                           loaded before the program.   libraries
                           and   an  ordered  list  of  candidate
                           libraries.
       lib*.so*            shared libraries

SEE ALSO
       ldd(d), ldconfig(g).

BUGS
       Currently ld.so has no means of  unloading  and  searching
       for compatible or newer version of libraries.

       ld.so functionality is only available for executables com-
       piled using libc version 4.4.3 or greater.

AUTHORS
       David Engel, Eric Youngdale, Peter MacDonald, Hongjiu  Lu,
       Linus Torvalds, Lars Wirzenius and Mitch D'Souza (not nec-
       essarily in that order).



                          14 March 1998                  ld.so(o)