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
       @LIBDIR@ 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 @CONFIGDIR@/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 @CONFIGDIR@/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

       @CONFIGDIR@/dll.aliases
              The list of aliased or hidden backends.

       @CONFIGDIR@/dll.conf
              The backend configuration file (see also description of SANE_CONFIG_DIR below).

       @LIBDIR@/libsane-dll.a
              The static library implementing this backend.

       @LIBDIR@/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 @CONFIGDIR@.  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 "@CONFIGDIR@" 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

@PACKAGEVERSION@                           13 Jul 2008                                sane-dll(5)