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sane-dll(5)              SANE Scanner Access Now Easy              sane-dll(5)

NAME
       sane-dll - SANE dynamic backend loader

DESCRIPTION
       The sane-dll library implements a SANE (Scanner Access Now Easy)
       backend that provides access to an arbitrary number of other SANE
       backends.  These backends may either be pre-loaded at the time the
       sane-dll library is built or, on systems that support dynamic loading
       of shared libraries, the backends may be loaded at runtime.  In the
       latter case, adding support for a new backend simply involves
       installing the relevant library in /usr/local/lib/sane and adding an
       entry to the dll.conf configuration file.  In other words, no
       applications need to be modified or recompiled to add support for new
       devices.

DEVICE NAMES
       This backend expects device names of the form:

              backend:device

       Where backend is the name of the backend and device is the name of the
       device in this backend that should be addressed.  If the device name
       does not contain a colon (:), then the entire string is treated as the
       device string for the default backend.  The default backend is the
       backend listed last in the configuration file (see below) or the first
       pre-loaded backend (if any).

CONFIGURATION
       The contents of the dll.conf file is a list of backend names that may
       be loaded dynamically upon demand.  Empty lines are ignored, also
       everything after a hash mark (#). A sample configuration file is shown
       below:

              net
              # this is a comment
              pnm
              mustek

       It is also possible to add a file in /usr/local/etc/sane.d/dll.d that
       contains the list of backends to be added. Backends mentioned in a file
       included in this directory will be added before any backends listed in
       dll.conf.  Files in /usr/local/etc/sane.d/dll.d can be freely named.
       They shall follow the format conventions as apply for dll.conf.

       Note that backends that were pre-loaded when building this library do
       not have to be listed in this configuration file.  That is, if a
       backend was preloaded, then that backend will always be present,
       regardless of whether it's listed in the configuration file or not.

       The list of preloaded backends is determined by macro
       PRELOADABLE_BACKENDS in file backend/Makefile.in of the SANE source
       code distribution.  After changing the value of this macro, it is
       necessary to reconfigure, rebuild, and reinstall SANE for the change to
       take effect.

       Aliases are defined in the config file dll.aliases.  It can contain
       entries of the form

              alias SomeName SaneDeviceName
              alias "Some Name" SaneDeviceName
              hide SaneDeviceName

       For example:

              alias Epson net:somehost:epson:/dev/sgX
              alias "Siemens ST400" st400:/dev/sgY
              hide net:somehost:pnm:0
              hide net:somehost:pnm:1
              alias "Read from file" pnm:0
              hide pnm:1

       Aliased device names are automatically hidden.

       The idea is that users don't have to deal with complicated device names
       (especially for networked devices), and to hide other exported devices
       which might confuse them. Note that a hidden device can still be
       accessed if the device name is known, it just doesn't appear on the
       list.

FILES
       /usr/local/etc/sane.d/dll.aliases
              The list of aliased or hidden backends.

       /usr/local/etc/sane.d/dll.conf
              The backend configuration file (see also description of
              SANE_CONFIG_DIR below).

       /usr/local/lib/sane/libsane-dll.a
              The static library implementing this backend.

       /usr/local/lib/sane/libsane-dll.so
              The shared library implementing this backend (present on systems
              that support dynamic loading).

ENVIRONMENT
       SANE_CONFIG_DIR
              This environment variable specifies the list of directories that
              may contain the configuration file.  Under UNIX, the directories
              are separated by a colon (`:'), under OS/2, they are separated
              by a semi-colon (`;').  If this variable is not set, the
              configuration file is searched in two default directories:
              first, the current working directory (".") and then in
              /usr/local/etc/sane.d.  If the value of the environment variable
              ends with the directory separator character, then the default
              directories are searched after the explicitly specified
              directories.  For example, setting SANE_CONFIG_DIR to
              "/tmp/config:" would result in directories "tmp/config", ".",
              and "/usr/local/etc/sane.d" being searched (in this order).

       SANE_DEBUG_DLL
              If the library was compiled with debug support enabled, this
              environment variable controls the debug level for this backend.
              E.g., a value of 128 requests all debug output to be printed.
              Smaller levels reduce verbosity.

              Value  Description
              0      print severe errors only
              1      print normal errors and important messages
              2      print normal messages
              3      print debugging messages
              4      print everything

              Example: export SANE_DEBUG_DLL=3

SEE ALSO
       sane(7), scanimage(1), sane-"backendname"(5)

AUTHOR
       David Mosberger

                                  13 Jul 2008                      sane-dll(5)