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
       option is specified more than once, or  in  case  of  a  conflict,  the
       rightmost 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:COM1,
                     serial:/dev/COM1, COM1, /dev/COM1.

              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
              device 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
              removed 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
              appropriate.

       -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
              parameter  is specified more than once then the rightmost speci-
              fication 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 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
              updated.  The built-in default is //var/lib/brltty.

       -V (--version)
              Print the versions of brltty itself,  the  server  side  of  its
              application  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 6.8.

       -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=)
              option 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
              details.

       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
              details.

       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

              dp  DotPad

              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 6.8                       February 2026                       BRLTTY(1)
