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,
 although the file format remains supported by less itself.

DESCRIPTION

 A lesskey file specifies a set of key bindings and environment
 variables 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 are ignored. Any text that follows an unescaped hash mark
 (#) in a line is ignored, except 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 <whitespace> [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 lists in the EXAMPLE sections
 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 followed 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
 character is to be taken literally. Characters which must be
 preceded by backslash include caret, space, tab, hash mark and the
 backslash itself.
 An action may be followed by an "extra" string. When such a
 command 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
 status.

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
 ^E forw-line
 ^N forw-line
 k back-line
 y back-line
 ^Y back-line
 ^K back-line
 ^P back-line
 J forw-line-force
 K back-line-force
 Y back-line-force
 \ej forw-newline
 \ek back-newline
 d forw-scroll
 ^D forw-scroll
 u back-scroll
 ^U back-scroll
 40円 forw-screen
 f forw-screen
 ^F forw-screen
 ^V forw-screen
 \kD forw-screen
 b back-screen
 ^B back-screen
 \ev back-screen
 \kU back-screen
 z forw-window
 w back-window
 \e40円 forw-screen-force
 \eb back-screen-force
 F forw-forever
 \eF forw-until-hilite
 R repaint-flush
 r repaint
 ^R repaint
 ^L 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 []
 \e^F forw-bracket
 \e^B back-bracket
 G goto-end
 \e> goto-end
 > goto-end
 \ke goto-end
 \eG goto-end-buffered
 = status
 ^G 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
 ^O^N osc8-forw-search
 ^On osc8-forw-search
 ^O^P osc8-back-search
 ^Op osc8-back-search
 ^O^O osc8-open
 & filter
 m set-mark
 M set-mark-bottom
 \em clear-mark
 ' goto-mark
 ^X^X goto-mark
 E examine
 :e examine
 ^X^V 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
 \e[M mouse
 \e[< mouse6
 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
 commands. A default command key may be disabled by including it in the
 input file with the action "invalid". Alternatively, a key may be
 defined to do nothing by using the action "noaction". "noaction" is
 similar 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円 back-complete
 \e\t back-complete
 ^L expand
 ^V literal
 ^A 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
 ^G abort
 \e[M mouse
 \e[< mouse6

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
 appended 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 variables. 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 whitespace 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
 replaced 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
 using a simple text comparison; no metacharacters are supported. An
 instance of slash or right curly bracket in STRING or REPL must be
 escaped by preceding it with two backslashes. If REPL is an empty
 string, all instances of STRING are removed. A slash immediately
 before 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
 version 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円 in a lesskey file.

COPYRIGHT

 Copyright (C) 1984-2025 Mark Nudelman
 less is part of the GNU project and is free software. You can
 redistribute it and/or modify it under the terms of either (1) the GNU
 General 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
 FITNESS 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 678: 01 May 2025 lesskey(1)