sane-dll.5

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
       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 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.  On *NIX systems, the direc-
              tories are separated by a colon (`:'), under OS/2, they are sep-
              arated 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/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/local/etc/sane.d be-
              ing 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)