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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) 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 li-
       brary 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.

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 ev-
       erything	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	 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/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 en-
       tries 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  ac-
       cessed 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 config-
	      uration  file is searched	in two default directories: first, the
	      current  working	directory   (".")   and	  then	 in   /usr/lo-
	      cal/etc/sane.d.	If  the	value of the environment variable ends
	      with the directory separator character, then the default	direc-
	      tories  are searched after the explicitly	specified directories.
	      For example, setting SANE_CONFIG_DIR to "/tmp/config:" would re-
	      sult   in	  directories	"tmp/config",	".",   and   "/usr/lo-
	      cal/etc/sane.d" being searched (in this order).

       SANE_DEBUG_DLL
	      If the library was compiled with debug support enabled, this en-
	      vironment	 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)

NAME | DESCRIPTION | DEVICE NAMES | CONFIGURATION | FILES | ENVIRONMENT | SEE ALSO | AUTHOR

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