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 back-
       ends.  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/lib64/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

       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 distribu-
       tion.  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

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

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

       /usr/lib64/sane/libsane-dll.a
	      The static library implementing this backend.

       /usr/lib64/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 configura-
	      tion file is searched in two default directories: first, the current working directory (".") and then in /etc/sane.d.  If the  value
	      of the environment variable ends with the directory separator character, then the default directories are searched after the explic-
	      itly specified directories.  For example, setting SANE_CONFIG_DIR to "/tmp/config:" would result in directories  "tmp/config",  ".",
	      and "/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)