BRLTTY(1) BRLTTY User's Manual BRLTTY(1)
NAME
brltty - refreshable braille display driver for Linux/Unix
SYNOPSIS
brltty [option ...]
DESCRIPTION
brltty is a background process (daemon) which provides access to the
console screen (when in text mode) for a blind person using a refresh-
able braille display. It drives the braille display, and provides com-
plete screen review functionality. Some speech capability has also
been incorporated.
OPTIONS
Options can be passed to brltty in a number of ways. From most to
least influential, these are:
1. Command Line Options
2. Boot Parameters
3. Environment Variables (if the -E (--environment-variables) option
is in effect)
4. The Configuration File
5. Built-in Defaults
Command Line Options
The options are processed sequentially from left to right. If an op-
tion is specified more than once, or in case of a conflict, the right-
most specification takes precedence.
The following options are supported:
-a table (--attributes-table=)
The path to the attributes table. Relative paths are anchored
at /etc/brltty/Attributes. The .atb extension is optional. The
built-in default is left_right.atb.
-b driver,...|auto (--braille-driver=)
The driver for the braille display (see Driver Specification).
The built-in default is auto.
-c table (--contraction-table=)
The path to the contraction table. Relative paths are anchored
at /etc/brltty/Contraction. The .ctb extension is optional.
-d device,... (--braille-device=)
The device to which the braille display is connected. The
built-in default is usb:,bluetooth:.
The general form of a braille device specification is quali-
fier:data. For backward compatibility with earlier releases, if
the qualifier is omitted then serial: is assumed. The following
device types are supported:
Bluetooth
For a bluetooth device, specify bluetooth:address. The
address must be six two-digit hexadecimal numbers sepa-
rated by colons, e.g. 01:23:45:67:89:AB.
Serial For a serial device, specify serial:device. The serial:
qualifier is optional (for backward compatibility). If a
relative path is given then it's anchored at /dev/ (the
usual location where devices are defined on a Unix-like
system). The following device specifications all refer
to the primary serial device on Linux: serial:ttyS0, se-
rial:/dev/ttyS0, ttyS0, /dev/ttyS0.
USB For a USB device, specify usb:. brltty will search for
the first USB device which matches the braille display
driver being used. If this is inadequate, e.g. if you
have more than one USB braille display which requires the
same driver, then you can refine the device specification
by appending the serial number of the display to it, e.g.
usb:12345. N.B.: The "identification by serial number"
feature doesn't work for some models because some manu-
facturers either don't set the USB serial number descrip-
tor at all or do set it but not to a unique value.
A comma-delimited list of braille devices may be specified. If
this is done then autodetection is performed on each listed de-
vice in sequence. This feature is particularly useful if you
have a braille display with more than one interface, e.g. both a
serial and a USB port.
-e (--standard-error)
Write logs to standard error rather than to the system log (use-
ful for debugging).
-f file (--configuration-file=)
The path to the configuration file. Relative paths are anchored
at the current working directory. The built-in default is
/etc/brltty.conf.
-h (--help)
Print a command line usage summary (commonly used options only),
and then exit.
-i name (--speech-input=)
The file system object (FIFO, named pipe, named socket, etc)
which gives other applications access to brltty's speech driver
for text-to-speech conversion. It's created at start-up and re-
moved at termination. Relative paths are anchored at the cur-
rent working directory. The built-in default is that the file
system object is not created.
-k table (--keyboard-table=)
The path to the keyboard table. Relative paths are anchored at
/etc/brltty/Keyboard. The .ktb extension is optional.
-l level (--log-level=)
The minimum severity level for messages written to the log. Any
of the following numbers, or any abbreviation of their corre-
sponding names, may be specified:
0 emergency
1 alert
2 critical
3 error
4 warning
5 notice
6 information
7 debug
The built-in default is notice.
-m device (--midi-device=)
The device to use for the Musical Instrument Digital Interface.
For ALSA it's client:port, where each may be either a number or
a case-sensitive substring of its name. For other interfaces
it's the full path to an appropriate system device. The built-
in default is:
Linux/ALSA the first available MIDI output port
Linux/OSS /dev/sequencer
-n (--no-daemon)
Remain in the foreground (useful for debugging).
-o name=value,... (--override-preference=)
Override a preference setting. For the location of the prefer-
ences file, see the -F (--preferences-file) option.
-p device (--pcm-device=)
The device to use for digital audio. For ALSA it's name[:argu-
ment,...]. For other interfaces it's the full path to an appro-
priate system device. The built-in default is:
FreeBSD /dev/dsp
Linux/ALSA hw:0,0
Linux/OSS /dev/dsp
NetBSD /dev/audio
OpenBSD /dev/audio
Qnx the preferred PCM output device
Solaris /dev/audio
-q (--quiet)
Suppress the start-up messages. This is done by reducing the
default log level (see the -l (--log-level=) option) to warning
(information if either -v (--verify) or -V (--version) is also
specified).
-r (--release-device)
Release the device to which the braille display is connected
when the current screen or window can't be read.
-s driver,...|auto (--speech-driver=)
The driver for the speech synthesizer (see Driver Specifica-
tion). The built-in default is auto.
-t table (--text-table=)
The path to the text table. Relative paths are anchored at
/etc/brltty/Text. The .ttb extension is optional. The built-in
default is en-nabcc.ttb (the North American Braille Computer
Code).
-v (--verify)
Print the start-up messages and then exit. This always includes
the versions of brltty itself, the server side of its applica-
tion programming interface, and each of the selected braille and
speech drivers. If the -q (--quiet) option isn't also specified
then it also includes the values of the options after all
sources have been considered. If more than one braille driver
and/or more than one braille device has been specified then
braille display autodetection is performed. If more than one
speech driver has been specified then speech synthesizer autode-
tection is performed.
-x driver (--screen-driver=)
The screen driver. The built-in default is operating system ap-
propriate.
-A name=value,... (--api-parameters=)
Parameters for the application programming interface. If the
same parameter is specified more than once then the rightmost
specification is used. Parameter names may be abbreviated.
-B [driver:]name=value,... (--braille-parameters=)
Parameters for the braille display driver. If the same parame-
ter is specified more than once then the rightmost specification
is used. Parameter names may be abbreviated. If a parameter
assignment is qualified with a driver identification code then
it's only processed if that braille display driver is being
used.
-D directory (--drivers-directory=)
The path to the directory which contains the dynamically load-
able driver objects. The built-in default is /lib/brltty.
-E (--environment-variables)
Recognize environment variables.
-F file (--preferences-file=)
The path to the preferences file. Relative paths are anchored
at /var/lib/brltty. The built-in default is brltty.prefs.
-H (--full-help)
Print a command line usage summary (all options), and then exit.
-I (--install-service)
(Windows only) Install brltty as the BrlAPI service so that it
will be automatically started when the system is booted, and so
that applications can know that a BrlAPI server is running.
-K arg (--keyboard-properties=)
Properties of the keyboard.
-L file (--log-file=)
The file to which log messages are written. Relative paths are
anchored at the current working directory. The default is to
send log messages to the system log.
-M csecs (--message-delay=)
The message hold time in hundredths of a second. The built-in
default is 400 (4 seconds).
-N (--no-api)
Don't start the application programming interface.
-P file (--pid-file=)
The full path to the process identifier file. If this option is
supplied, brltty writes its process identifier (pid) into the
specified file at start-up. The file is removed when brltty
terminates.
-R (--remove-service)
(Windows only) Remove the BrlAPI service so that brltty will not
be automatically started when the system is booted, and so that
applications can know that no BrlAPI server is running.
-S [driver:]name=value,... (--speech-parameters=)
Parameters for the speech synthesizer driver. If the same pa-
rameter is specified more than once then the rightmost specifi-
cation is used. Parameter names may be abbreviated. If a pa-
rameter assignment is qualified with a driver identification
code then it's only processed if that speech synthesizer driver
is being used.
-T directory (--tables-directory=)
The path to the directory which contains the text, contraction,
attributes, keyboard, and input tables. The built-in default is
/etc/brltty.
-U directory (--updatable-directory=)
The path to a directory which contains files that can be up-
dated. The built-in default is /var/lib/brltty.
-V (--version)
Print the versions of brltty itself, the server side of its ap-
plication programming interface, and those drivers which were
configured in at build-time, and then exit. If the -q (--quiet)
option isn't also specified then also print copyright informa-
tion.
-W directory (--writable-directory=)
The path to a directory which can be written to. The built-in
default is /run/brltty.
-X name=value,... (--screen-parameters=)
Parameters for the screen driver. If the same parameter is
specified more than once then the rightmost specification is
used. Parameter names may be abbreviated.
-Y text (--start-message=)
The text to be shown when the braille driver starts and to be
spoken when the speech driver starts. The built-in default is
BRLTTY 6.4.
-Z text (--stop-message=)
The text to be shown when the braille driver stops. The built-
in default is BRLTTY stopped.
Environment Variables
The following environment variables are recognized if the -E (--envi-
ronment-variables) option is specified:
BRLTTY_API_PARAMETERS=name=value,...
Parameters for the application programming interface. See the
-A (--api-parameters=) option for details.
BRLTTY_ATTRIBUTES_TABLE=table
The attributes table. See the -a (--attributes-table=) option
for details.
BRLTTY_BRAILLE_DEVICE=device,...
The device to which the braille display is connected. See the
-d (--braille-device=) option for details.
BRLTTY_BRAILLE_DRIVER=driver,...|auto
The driver for the braille display. See the -b
(--braille-driver=) option for details.
BRLTTY_BRAILLE_PARAMETERS=[driver:]name=value,...
Parameters for the braille display driver. See the -B
(--braille-parameters=) option for details.
BRLTTY_CONFIGURATION_FILE=file
The configuration file. See the -f (--configuration-file=) op-
tion for details.
BRLTTY_CONTRACTION_TABLE=table
The contraction table. See the -c (--contraction-table=) option
for details.
BRLTTY_MIDI_DEVICE=device
The device to use for the Musical Instrument Digital Interface.
See the -m (--midi-device=) option for details.
BRLTTY_PCM_DEVICE=device
The device to use for digital audio. See the -p (--pcm-device=)
option for details.
BRLTTY_PREFERENCES_FILE=file
The preferences file. See the -F (--preferences-file=) option
for details.
BRLTTY_RELEASE_DEVICE=on|off
Release the device to which the braille display is connected
when the current screen or window can't be read. See the -r
(--release-device) option for details.
BRLTTY_SCREEN_DRIVER=driver
The screen driver. See the -x (--screen-driver=) option for de-
tails.
BRLTTY_SCREEN_PARAMETERS=name=value,...
Parameters for the screen driver. See the -X (--screen-parame-
ters=) option for details.
BRLTTY_SPEECH_DRIVER=driver,...|auto
The driver for the speech synthesizer. See the -s
(--speech-driver=) option for details.
BRLTTY_SPEECH_INPUT=name
The file system object which gives other applications access to
brltty's speech driver for text-to-speech conversion. See the
-i (--speech-input=) option for details.
BRLTTY_SPEECH_PARAMETERS=[driver:]name=value,...
Parameters for the speech synthesizer driver. See the -S
(--speech-parameters=) option for details.
BRLTTY_TEXT_TABLE=table
The text table. See the -t (--text-table=) option for details.
The Configuration File
Blank lines are ignored. If the character # occurs on any line then
all characters from it to the end of that line are treated as a com-
ment.
The following configuration directives are supported:
api-parameters name=value,...
Parameters for the application programming interface. See the
-A (--api-parameters=) option for details.
attributes-table table
The attributes table. See the -a (--attributes-table=) option
for details.
braille-device device,...
The device to which the braille display is connected. See the
-d (--braille-device=) option for details.
braille-driver driver,...|auto
The driver for the braille display. See the -b
(--braille-driver=) option for details.
braille-parameters [driver:]name=value,...
Parameters for the braille display driver. See the -B
(--braille-parameters=) option for details.
contraction-table table
The contraction table. See the -c (--contraction-table=) option
for details.
midi-device device
The device to use for the Musical Instrument Digital Interface.
See the -m (--midi-device=) option for details.
pcm-device device
The device to use for digital audio. See the -p (--pcm-device=)
option for details.
preferences-file file
The preferences file. See the -F (--preferences-file=) option
for details.
release-device on|off
Release the device to which the braille display is connected
when the current screen or window can't be read. See the -r
(--release-device) option for details.
screen-driver driver
The screen driver. See the -x (--screen-driver=) option for de-
tails.
screen-parameters name=value,...
Parameters for the screen driver. See the -X (--screen-parame-
ters=) option for details.
speech-driver driver,...|auto
The driver for the speech synthesizer. See the -s
(--speech-driver=) option for details.
speech-input 0me
The file system object which gives other applications access to
brltty's speech driver for text-to-speech conversion. See the
-i (--speech-input=) option for details.
speech-parameters [driver:]name=value,...
Parameters for the speech synthesizer driver. See the -S
(--speech-parameters=) option for details.
text-table table
The text table. See the -t (--text-table=) option for details.
Driver Specification
A braille display or speech synthesizer driver must be specified via
its identification code:
al Alva
an Android
at Albatross
ba BrlAPI
bc BrailComm
bd Braudi
bl BrailleLite
bm Baum
bn BrailleNote
cb CombiBraille
ce Cebra
cn Canute
ec EcoBraille
en eSpeak-NG
es eSpeak
eu EuroBraille
fa FrankAudiodata
fl FestivalLite
fs FreedomScientific
fv Festival
gs GenericSay
hd Hedo
hm HIMS
ht HandyTech
hw HumanWare
ir Iris
ic Inceptor
lb Libbraille
lt LogText
mb MultiBraille
md MDV
mm BrailleMemo
mn MiniBraille
mp Mikropuhe
mt Metec
no no driver
np NinePoint
pg Pegasus
pm Papenmeier
sd SpeechDispatcher
sk Seika
sw Swift
th Theta
tn TechniBraille Systems Inc.
ts Telesensory Systems Inc.
vd VideoBraille
vo Voyager, Part232 (serial adapter), BraillePen/EasyLink
vs VisioBraille
vv ViaVoice
xs ExternalSpeech
A comma-delimited list of drivers may be specified. If this is
done then autodetection is performed using each listed driver in
sequence. You may need to experiment in order to determine the
most reliable order since some drivers autodetect better than
others.
If the single word auto is specified then autodetection is per-
formed using only those drivers which are known to be reliable
for this purpose.
SEE ALSO
For full documentation, see brltty's on-line manual at
[http://brltty.app/documentation.html].
brltty 6.4 September 2021 BRLTTY(1)
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