update_prebinding file ...-root directory [-pkgs package-name install-
                       location ...] [-files filename ...] [-debug]

DESCRIPTION

     update_prebinding tries to synchronize prebinding information for li-
     braries and executables when new files are added to a system.  Prebinding
     information is pre-calculated address information for libraries used by a
     given executable or library.  By pre-determining where a function in an-
     other library is destined to be placed, the dynamic linker does not have
     to resolve symbols at application startup time, and the application can
     launch faster.

     Because each recompilation of a library or executable may place functions
     at different addresses, a newly installed library or executable's pre-
     binding information might not match the libraries already on the disk.
     When the dynamic linker determines determines that prebinding information
     for a library could be invalid, it defaults to resolving all the names
     for that library, and for all libraries referenced by that library, los-
     ing any advantage of having the prebinding information.

     update_prebinding ensures that prebinding information is up-to-date after
     new prebound applications or new versions of system libraries are in-
     stalled.  Given a list of the newly installed files in a package, up-
     date_prebinding finds all the libraries and executables that may dynami-
     cally load the changed files.  If so, the prebinding information must be
     updated, and update_prebinding performs redo_prebinding to update that
     file.  update_prebinding builds a dependency graph to minimize the files
     that must be updated, and applies a few other heuristics to only call
     redo_prebinding when necessary.

     The root argument specifies the directory tree to search for changed
     files.  This is usually the root directory.  update_prebinding will look
     for dependent libraries and executables within this directory hierarchy,
     but will not go to different file systems.  The argument allows you to
     update prebinding information for a specific file to match a non-running
     version of the operating system on another partition.  update_prebinding
     uses the root to find the system libraries for that version of the OS.
     The root argument is not intended to limit update_prebinding's effect to
     a particular set of executables; instead, you must specify the changed
     files using -files or -pkgs.

     The pkgs argument specifies the packages containing the files to be up-
     dated.  update_prebinding uses this list to determine the files that must
     change, and thus identify the scope of updates necessary.  After the op-
     tion name, list every package that changed, along with its install root
     so that update_prebinding can find the newly installed files.

     If no packages are named on the command line, then update_prebinding
     scans the entire directory hierarchy from the named root looking for exe-
     cutables, then prebinds all executables from least dependent to most.

     efits of prebinding as long as the system libraries used by the applica-
     tion have been correctly prebound.

     Updating prebinding for a given library or application can fail if any of
     its dependent libraries are invalid -- not prebound, expected load ad-
     dress conflicting with other loaded libraries, or missing architecture in
     a fat library.  To test if an application is able to use prebinding in-
     formation, set the environment variable DYLD_PREBIND_DEBUG.  (See dyld(1)
     for details on this option.)

     For efficiency, update_prebinding does not actually execute /usr/bin/re-
     do_prebinding for each file to be updated, but instead executes similar
     code within the update_prebinding process.

SEE ALSO

     dyld(1) redo_prebinding(1)

BSD Experimental               February 14, 2001                             2