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

       sane-dll	- SANE dynamic backend loader

       The  sane-dll library implements	a SANE (Scanner	Access Now Easy) back-
       end 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	 rele-
       vant library in /usr/local/lib/sane and adding an entry to the dll.conf
       configuration file.  In other words, no applications need to  be	 modi-
       fied or recompiled to add support for new devices.

       This backend expects device names of the	form:


       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).

       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

	      #	this is	a comment

       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	 back-
       end 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_BACK-
       ENDS  in	file backend/ 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

	      The list of aliased or hidden backends.

	      The  backend  configuration  file	 (see  also   description   of
	      SANE_CONFIG_DIR below).

	      The static library implementing this backend.

	      The shared library implementing this backend (present on systems
	      that support dynamic loading).

	      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 config-
	      uration 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 directo-
	      ries.   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).

	      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

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

       David Mosberger

				  13 Jul 2008			   sane-dll(5)


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