LESSKEY(1)                  General Commands Manual                 LESSKEY(1)

NAME
       lesskey - customize key bindings for less

SYNOPSIS (deprecated)
       lesskey [-o output] [--] [input]
       lesskey [--output=output] [--] [input]
       lesskey -V
       lesskey --version

SCOPE
       This document describes the format of the lesskey source file, which is
       used  by  less  version 582 and later.  In previous versions of less, a
       separate program called lesskey was used to compile the lesskey  source
       file  into  a  format  understood by less.  This compilation step is no
       longer required and the lesskey program is  therefore  deprecated,  al‐
       though the file format remains supported by less itself.

DESCRIPTION
       A  lesskey  file  specifies a set of key bindings and environment vari‐
       ables to be used by subsequent invocations of less.

FILE FORMAT
       The input file consists of one or more sections.  Each  section  starts
       with  a  line  that  identifies the type of section.  Possible sections
       are:

       #command
              Customizes command key bindings.

       #line‐edit
              Customizes line‐editing key bindings.

       #env   Defines environment variables.

       Blank lines and lines which start with a hash mark (#) are ignored, ex‐
       cept as noted below.

COMMAND SECTION
       The command section begins with the line

       #command

       If the command section is the first section in the file, this line  may
       be omitted.  The command section consists of lines of the form:

            string <whitespace> action [extra‐string] <newline>

       Whitespace  is  any  sequence  of  one or more spaces and/or tabs.  The
       string is the command key(s) which invoke the action.  The  string  may
       be a single command key, or a sequence of up to 15 keys.  The action is
       the  name  of  the less action, from the list below.  The characters in
       the string may appear literally, or be prefixed by a caret to  indicate
       a  control  key.  A backslash followed by one to three octal digits may
       be used to specify a character by its octal value.   A  backslash  fol‐
       lowed by certain characters specifies input characters as follows:
            \b   BACKSPACE   (0x08)
            \e   ESCAPE      (0x1B)
            \n   NEWLINE     (0x0A)
            \r   RETURN      (0x0D)
            \t   TAB         (0x09)

            \k  followed by a single character represents the char(s) produced
            when one of these keys is pressed:
            \kb   BACKSPACE (the BACKSPACE key)
            \kB   ctrl‐BACKSPACE
            \kd   DOWN ARROW
            \kD   PAGE DOWN
            \ke   END
            \kh   HOME
            \ki   INSERT
            \kl   LEFT ARROW
            \kL   ctrl‐LEFT ARROW
            \kr   RIGHT ARROW
            \kR   ctrl‐RIGHT ARROW
            \kt   BACKTAB
            \ku   UP ARROW
            \kU   PAGE UP
            \kx   DELETE
            \kX   ctrl‐DELETE
            \k1   F1


            A backslash followed by any other character indicates that charac‐
            ter is to be taken literally.  Characters which must  be  preceded
            by  backslash  include  caret, space, tab, hash mark and the back‐
            slash itself.

            An action may be followed by an "extra" string.  When such a  com‐
            mand  is  entered while running less, the action is performed, and
            then the extra string is parsed, just as if it were  typed  in  to
            less.   This  feature  can  be used in certain cases to extend the
            functionality of a command.  For example, see  the  "{"  and  ":t"
            commands  in  the  example  below.  The extra string has a special
            meaning for the "quit" action: when less quits, the ASCII value of
            the first character of the extra string is used as its  exit  sta‐
            tus.

EXAMPLE
       The following input file describes the set of default command keys used
       by  less.   Documentation  on each command can be found in the less man
       page, under the key sequence which invokes the command.

            #command
            \r         forw‐line
            \n         forw‐line
            e          forw‐line
            j          forw‐line
            \kd        forw‐line
            ˆE         forw‐line
            ˆN         forw‐line
            k          back‐line
            y          back‐line
            ˆY         back‐line
            ˆK         back‐line
            ˆP         back‐line
            J          forw‐line‐force
            K          back‐line‐force
            Y          back‐line‐force
            d          forw‐scroll
            ˆD         forw‐scroll
            u          back‐scroll
            ˆU         back‐scroll
            \40        forw‐screen
            f          forw‐screen
            ˆF         forw‐screen
            ˆV         forw‐screen
            \kD        forw‐screen
            b          back‐screen
            ˆB         back‐screen
            \ev        back‐screen
            \kU        back‐screen
            z          forw‐window
            w          back‐window
            \e\40      forw‐screen‐force
            F          forw‐forever
            \eF        forw‐until‐hilite
            R          repaint‐flush
            r          repaint
            ˆR         repaint
            ˆL         repaint
            \eu        undo‐hilite
            \eU        clear‐search
            g          goto‐line
            \kh        goto‐line
            <          goto‐line
            \e<        goto‐line
            p          percent
            %          percent
            \e(        left‐scroll
            \e)        right‐scroll
            \kl        left‐scroll
            \kr        right‐scroll
            \e{        no‐scroll
            \e}        end‐scroll
            {          forw‐bracket {}
            }          back‐bracket {}
            (          forw‐bracket ()
            )          back‐bracket ()
            [          forw‐bracket []
            ]          back‐bracket []
            \eˆF       forw‐bracket
            \eˆB       back‐bracket
            G          goto‐end
            \e>        goto‐end
            >          goto‐end
            \ke        goto‐end
            \eG        goto‐end‐buffered
            =          status
            ˆG         status
            :f         status
            /          forw‐search
            ?          back‐search
            \e/        forw‐search *
            \e?        back‐search *
            n          repeat‐search
            \en        repeat‐search‐all
            N          reverse‐search
            \eN        reverse‐search‐all
            ˆOˆN       osc8‐forw‐search
            ˆOn        osc8‐forw‐search
            ˆOˆP       osc8‐back‐search
            ˆOp        osc8‐back‐search
            ˆOˆO       osc8‐open
            &          filter
            m          set‐mark
            M          set‐mark‐bottom
            \em        clear‐mark
            ’          goto‐mark
            ˆXˆX       goto‐mark
            E          examine
            :e         examine
            ˆXˆV       examine
            :n         next‐file
            :p         prev‐file
            t          next‐tag
            T          prev‐tag
            :x         index‐file
            :d         remove‐file
            ‐          toggle‐option
            :t         toggle‐option t
            s          toggle‐option o
                       ## Use a long option name by starting the
                       ## extra string with ONE dash; eg:
                       ##   s toggle‐option ‐log‐file\n
            _          display‐option
            |          pipe
            v          visual
            !          shell
            #          pshell
            +          firstcmd
            H          help
            h          help
            V          version
            0          digit
            1          digit
            2          digit
            3          digit
            4          digit
            5          digit
            6          digit
            7          digit
            8          digit
            9          digit
            q          quit
            Q          quit
            :q         quit
            :Q         quit
            ZZ         quit


PRECEDENCE
       Commands specified by lesskey take precedence  over  the  default  com‐
       mands.   A  default  command key may be disabled by including it in the
       input file with the action "invalid".  Alternatively, a key may be  de‐
       fined to do nothing by using the action "noaction".  "noaction" is sim‐
       ilar  to  "invalid",  but less will give an error beep for an "invalid"
       command, but not for a "noaction" command.  In  addition,  ALL  default
       commands may be disabled by adding this control line to the input file:

       #stop

       This  will  cause  all  default commands to be ignored.  The #stop line
       should be the last line in that section of the file.

       Be aware that #stop can be dangerous.  Since all default  commands  are
       disabled, you must provide sufficient commands before the #stop line to
       enable all necessary actions.  For example, failure to provide a "quit"
       command can lead to frustration.

LINE EDITING SECTION
       The line‐editing section begins with the line:

       #line‐edit

       This  section specifies new key bindings for the line editing commands,
       in a manner similar to the way key bindings for ordinary  commands  are
       specified  in  the #command section.  The line‐editing section consists
       of a list of keys and actions, one per line as in the example below.

EXAMPLE
       The following input file describes the set of default line‐editing keys
       used by less:

            #line‐edit
            \t           forw‐complete
            \17          back‐complete
            \e\t         back‐complete
            ˆL           expand
            ˆV           literal
            ˆA           literal
            \el          right
            \kr          right
            \eh          left
            \kl          left
            \eb          word‐left
            \e\kl        word‐left
            \ew          word‐right
            \e\kr        word‐right
            \ei          insert
            \ex          delete
            \kx          delete
            \eX          word‐delete
            \ekx         word‐delete
            \e\b         word‐backspace
            \e0          home
            \kh          home
            \e$          end
            \ke          end
            \ek          up
            \ku          up
            \ej          down
            ˆG           abort


LESS ENVIRONMENT VARIABLES
       The environment variable section begins with the line

       #env

       Following this line is a  list  of  environment  variable  assignments.
       Each  line consists of an environment variable name, an equals sign (=)
       and the value to be assigned to the environment variable.  White  space
       before  and  after  the  equals sign is ignored.  Variables assigned in
       this way are visible only to less.  If a variable is specified  in  the
       system environment and also in a lesskey file, the value in the lesskey
       file takes precedence.

       If the variable name is followed by += rather than =, the string is ap‐
       pended  to the variable’s existing value.  This currently works only if
       any += lines immediately follow the same variable’s original definition
       (with an = line), without any intervening definitions  of  other  vari‐
       ables.   It  can append only to a variable defined earlier in the file;
       it cannot append to a variable in the system environment.   The  string
       is appended literally, without any extra whitespace added, so if white‐
       space  is  desired,  it  should be appended to the end of the preceding
       line.  (It cannot be added to the beginning of the  +=  string  because
       space after the equals sign is ignored, as noted above.)

       In  the string after the = sign, a substring of the form ${NAME} is re‐
       placed with the value of the environment variable "NAME".  The value of
       the variable may come from either the system  environment,  an  earlier
       lesskey  file,  or  an  earlier definition in the current lesskey file.
       Simple  text  replacements  can  be  performed  by  using  the   syntax
       ${NAME/STRING/REPL}.   This  replaces  all instances of "STRING" in the
       named environment variable with the text "REPL".  STRING is matched us‐
       ing a simple text comparison; no metacharacters are supported.  An  in‐
       stance  of  slash  or right curly bracket in STRING or REPL must be es‐
       caped by preceding it with  two  backslashes.   If  REPL  is  an  empty
       string,  all  instances of STRING are removed.  A slash immediately be‐
       fore the right curly bracket may be omitted.  Multiple replacements may
       be performed by using  the  syntax  ${NAME/STRING1/REPL1/STRING2/REPL2}
       and so on.

CONDITIONAL CONFIGURATION
       If  a line begins with #version followed by a relational operator and a
       version number, the remainder of the line is parsed if and only if  the
       running version of less (or lesskey) matches the operator.  This can be
       helpful if a lesskey file is used by different versions of less.

       For  example,  suppose  that  a  new command named ’sideways‐search’ is
       added in less version 777.  Then the following line  would  assign  the
       command  to  the  Q key, but only in versions of less which support it.
       The line would be ignored by versions earlier than 777.

            #version >= 777  Q sideways‐search

       These six operators are supported:
             >    Greater than
             <    Less than
             >=   Greater than or equal to
             <=   Less than or equal to
             =    Equal to
             !=   Not equal to

       The #version feature is not supported in less and lesskey  before  ver‐
       sion 594.  In those older versions, all #version lines are ignored.

EXAMPLE
       The  following  input  file sets the -i and -S options when less is run
       and, on version 595 and higher, adds a --color option.

            #env
            ## (Note that there must be a space at the end of the next line,
            ##  to separate the ‐‐color option from the ‐S option.)
            LESS = -i -S
            #version >= 595  LESS += --color=Hkc

SEE ALSO
       less(1)

WARNINGS
       On MS‐DOS and OS/2 systems, certain keys send a sequence of  characters
       which  start  with  a  NUL character (0).  This NUL character should be
       represented as \340 in a lesskey file.

COPYRIGHT
       Copyright (C) 1984‐2024  Mark Nudelman

       less is part of the GNU project and is free software.  You  can  redis‐
       tribute  it and/or modify it under the terms of either (1) the GNU Gen‐
       eral Public License as published by the Free  Software  Foundation;  or
       (2) the Less License.  See the file README in the less distribution for
       more details regarding redistribution.  You should have received a copy
       of  the  GNU General Public License along with the source for less; see
       the file COPYING.  If not, write to the Free  Software  Foundation,  59
       Temple  Place, Suite 330, Boston, MA  02111‐1307, USA.  You should also
       have received a copy of the Less License; see the file LICENSE.

       less is distributed in the hope that it will be useful, but WITHOUT ANY
       WARRANTY; without even the implied warranty of MERCHANTABILITY or  FIT‐
       NESS  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
       more details.

AUTHOR
       Mark Nudelman
       Report bugs at https://github.com/gwsw/less/issues.

                           Version 668: 06 Oct 2024                 LESSKEY(1)