LESSKEY(1) User Commands 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 and lines which start with a hash mark (#) are 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 [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 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
d forw-scroll
^D forw-scroll
u back-scroll
^U back-scroll
\40 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
\e\40 forw-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
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 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

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 in a lesskey file.

COPYRIGHT

Copyright (C) 1984-2024 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 661: 29 Jun 2024 LESSKEY(1)