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 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  relevant  library  in  /usr/lib/sane  and
       adding  an  entry  to the dll.conf configuration file.  In
       other words, no applications need to be modified or recom­
       piled 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 and lines starting with a hash mark (#) are ignored.
       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 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 "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 descrip­
              tion 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  (pre­
              sent 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
              configuration  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 directo­
              ries.   For  example,  setting  SANE_CONFIG_DIR  to
              "/tmp/config:"    would   result   in   directories

              (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.


SEE ALSO

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


AUTHOR

       David Mosberger


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