sane-dll - SANE dynamic backend loader
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 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 and lines starting with
a hash mark (#) are ignored. A sample configuration file is shown
# this is a comment
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_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
alias Epson net:somehost:epson:/dev/sgX
alias "Siemens ST400" st400:/dev/sgY
alias "Read from file" pnm:0
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
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 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 separator
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
SANE_DEBUG_DLL [Toc] [Back]
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.
0 print severe errors only
1 print normal errors and important messages
2 print normal messages
3 print debugging messages
4 print everything
sane(7), scanimage(1), sane-"backendname"(5)
11 Nov 2001 sane-dll(5)
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