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 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, 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 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 charac-
ter 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 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" com-
mands 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 "in-
valid", 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 be-
fore 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 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 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 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 rep-
resented 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 re-
ceived 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)
Generated by dwww version 1.16 on Tue Dec 16 04:04:52 CET 2025.