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
       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/lib/sane and adding an entry to the dll.conf con-
       figuration 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  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
       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/lib/sane/libsane-dll.a
              The static library implementing this backend.

       /usr/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 /etc/sane.d.  If the
              value of the environment variable ends with the directory  sepa-
              rator 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 "/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)