Manual: lesskey
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 pre‐
vious 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 sec‐
tion. 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 action [extra-string]
Whitespace is any sequence of one or more spaces and/or tabs. The string is the command key(s) which invoke the ac‐
tion. 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 indi‐
cate a control key. A backslash followed by one to three octal digits may be used to specify a character by its oc‐
tal 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" com‐
mand, 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 vari‐
able "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 668: 06 Oct 2024 LESSKEY(1)