More powerful then you thought!
less [-[+]aBcCdeEfFgGiIJKLmMnNqQrRsSuUVwWX~]
[-b space] [-h lines] [-j line] [-k keyfile]
[-{oO} logfile]
[-p pattern] [-P prompt] [-t tag]
[-T tagsfile] [-x tab,...]
[-y lines] [-[z] lines]
[-# shift] [+[+]cmd] [--] [filename]…
After starting, commands are entered and may be preceded by n, a repeat count.
In the following descriptions: ^X means control-X.
␛ stands for the ESCAPE key;
For example ␛-v means the two character sequence ␛ , then "v".
f | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
less operates.-.
Most may be given as a dash followed by a single letter, or
two dashes followed by a long option name. which may be abbreviated as long as it is unambiguous. For example,
--quit-at-eof may be abbreviated --quit.
Long option names in uppercase, such as --QUIT-AT-EOF, are distinct from --quit-at-eof. need only
have their first letter capitalized; For example: --Quit-at-eof
Options are also taken from $LESS .
LESS="-options"; export LESSOn MS-windows, omit quotes, replace embedded percent signs by double percent signs.
$LESS is parsed before the command line, which will override the environment variable.
An option in $LESS , can be reset to its default value by beginning the command line option with -+
Options like -P -D take a string which must be terminaled with $
For example, to set two -D options on MS-DOS, use a dollar sign to terminate the string, like this:
LESS="-Dn9.1$-Ds4.1"
-F |
When entering command line at the bottom of the screen (for example, a filename for the :e command,
the pattern for
a search command), certain keys can be used to manipulate the command line. Most commands have an alternate form in [
brackets ] which can be used if a key does not exist on a particular keyboard. (Note that the forms beginning with ␛
do not work in some MS-DOS and Windows systems because ␛ is the line erase character.) Any of these special keys may
be entered literally by preceding it with the "literal" character, either ^V
^A. A backslash itself may also be
entered literally by entering two backslashes.
LEFTARROW [ ␛-h ]
Move the cursor one space to the left.
RIGHTARROW [ ␛-l ]
Move the cursor one space to the right.
^LEFTARROW [ ␛-b
␛-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.) Move the cursor one word to the left.
^RIGHTARROW [ ␛-w
␛-RIGHTARROW ]
(That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right.
HOME [ ␛-0 ]
Move the cursor to the beginning of the line.
END [ ␛-$ ]
Move the cursor to the end of the line.
BACKSPACE
Delete the character to the left of the cursor,
cancel the command if the command line is empty.
DELETE
[ ␛-x ]
Delete the character under the cursor.
^BACKSPACE [ ␛-BACKSPACE ]
(That is, CONTROL and BACKSPACE simultaneously.) Delete the word to the left of the cursor.
^DELETE [ ␛-X
␛-DELETE ]
(That is, CONTROL and DELETE simultaneously.) Delete the word under the cursor.
UPARROW [ ␛-k ]
Retrieve the previous command line.
DOWNARROW [ ␛-j ]
Retrieve the next command line.
TAB Complete the partial filename to the left of the cursor. If it matches more than one filename, the first match
is entered into the command line. Repeated TABs will cycle thru the other matching filenames. If the completed
filename is a directory, a "/" is appended to the filename. (On MS-DOS systems, a "\" is appended.) The environment variable LESSSEPARATOR can be used to specify a different character to append to a directory name.
BACKTAB [ ␛-TAB ]
Like, TAB, but cycles in the reverse direction thru the matching filenames.
^L Complete the partial filename to the left of the cursor. If it matches more than one filename, all matches are
entered into the command line (if they fit).
^U (Unix and OS/2)
␛ (MS-DOS)
Delete the entire command line,
cancel the command if the command line is empty. If you have changed your
line-kill character in Unix to something other than ^U, that character is used instead of ^U.
KEY BINDINGS
Define your own less commands by using the program lesskey (1) to create a lesskey file. This file specifies a
set of command keys and an action associated with each key. You may also use lesskey to change the line-editing keys
(see LINE EDITING), and to set environment variables. If the environment variable LESSKEY is set, less uses that as
the name of the lesskey file. Otherwise, less looks in a standard place for the lesskey file: On Unix systems, less
looks for a lesskey file called "$HOME/.less". On MS-DOS and Windows systems, less looks for a lesskey file called
"$HOME/_less", and if it is not found there, then looks for a lesskey file called "_less" in any directory specified in
the PATH environment variable. On OS/2 systems, less looks for a lesskey file called "$HOME/less.ini", and if it is
not found, then looks for a lesskey file called "less.ini" in any directory specified in the INIT environment variable,
and if it not found there, then looks for a lesskey file called "less.ini" in any directory specified in the PATH environment variable. See the lesskey manual page for more details.
A system-wide lesskey file may also be set up to provide key bindings. If a key is defined in both a local lesskey
file and in the system-wide file, key bindings in the local file take precedence over those in the system-wide file.
If the environment variable LESSKEY_SYSTEM is set, less uses that as the name of the system-wide lesskey file. Otherwise, less looks in a standard place for the system-wide lesskey file: On Unix systems, the system-wide lesskey file is
/usr/local/etc/sysless. (However, if less was built with a different sysconf directory than /usr/local/etc, that
directory is where the sysless file is found.) On MS-DOS and Windows systems, the system-wide lesskey file is c:\_sysless. On OS/2 systems, the system-wide lesskey file is c:\sysless.ini.
INPUT PREPROCESSOR
You may define an "input preprocessor" for less. Before less opens a file, it first gives your input preprocessor a
chance to modify the way the contents of the file are displayed. An input preprocessor is simply an executable program
(or shell script), which writes the contents of the file to a different file, called the replacement file. The contents of the replacement file are then displayed in place of the contents of the original file. However, it will
appear to the user as if the original file is opened; that is, less will display the original filename as the name of
the current file.
An input preprocessor receives one command line argument, the original filename, as entered by the user. It should
create the replacement file, and when finished, print the name of the replacement file to its standard output. If the
input preprocessor does not output a replacement filename, less uses the original file, as normal. The input preprocessor is not called when viewing standard input. To set up an input preprocessor, set the LESSOPEN environment
variable to a command line which will invoke your input preprocessor. This command line should include one occurrence
of the string "%s", which will be replaced by the filename when the input preprocessor command is invoked.
When less closes a file opened in such a way, it will call another program, called the input postprocessor, which may
perform any desired clean-up action (such as deleting the replacement file created by LESSOPEN). This program receives
two command line arguments, the original filename as entered by the user, and the name of the replacement file. To set
up an input postprocessor, set the LESSCLOSE environment variable to a command line which will invoke your input post processor. It may include two occurrences of the string "%s"; the first is replaced with the original name of the file
and the second with the name of the replacement file, which was output by LESSOPEN.
For example, on many Unix systems, these two scripts will allow you to keep files in compressed format, but still let
less view them directly:
lessopen.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -
if [ -s /tmp/less.$$ ]; then
echo /tmp/less.$$
else
rm -f /tmp/less.$$
fi
;;
esac
lessclose.sh:
#! /bin/sh
rm $2
To use these scripts, put them both where they can be executed and set LESSOPEN="lessopen.sh %s", and LESSCLOSE="lessclose.sh %s %s". More complex LESSOPEN and LESSCLOSE scripts may be written to accept other types of compressed files,
and so on.
It is also possible to set up an input preprocessor to pipe the file data directly to less, rather than putting the
data into a replacement file. This avoids the need to decompress the entire file before starting to view it. An input
preprocessor that works this way is called an input pipe. An input pipe, instead of writing the name of a replacement
file on its standard output, writes the entire contents of the replacement file on its standard output. If the input
pipe does not write any characters on its standard output, then there is no replacement file and less uses the original
file, as normal. To use an input pipe, make the first character in the LESSOPEN environment variable a vertical bar
(|) to signify that the input preprocessor is an input pipe.
For example, on many Unix systems, this script will work like the previous example scripts:
lesspipe.sh:
#! /bin/sh
case "$1" in
*.Z) uncompress -c $1 2>/dev/null
;;
esac
To use this script, put it where it can be executed and set LESSOPEN="|lesspipe.sh %s". When an input pipe is used, a
LESSCLOSE postprocessor can be used, but it is usually not necessary since there is no replacement file to clean up.
In this case, the replacement file name passed to the LESSCLOSE postprocessor is "-".
NATIONAL CHARACTER SETS
There are three types of characters in the input file:
normal characters
can be displayed directly to the screen.
control characters
should not be displayed directly, but are expected to be found in ordinary text files (such as backspace and
tab).
binary characters
should not be displayed directly and are not expected to be found in text files.
A "character set" is simply a description of which characters are to be considered normal, control, and binary. The
LESSCHARSET environment variable may be used to select a character set. Possible values for LESSCHARSET are:
ascii BS, TAB, NL, CR, and formfeed are control characters, all chars with values between 32 and 126 are normal, and
all others are binary.
iso8859
Selects an ISO 8859 character set. This is the same as ASCII, except characters between 160 and 255 are treated
as normal characters.
latin1 Same as iso8859.
latin9 Same as iso8859.
dos Selects a character set appropriate for MS-DOS.
ebcdic Selects an EBCDIC character set.
IBM-1047
Selects an EBCDIC character set used by OS/390 Unix Services. This is the EBCDIC analogue of latin1. You get
similar results by setting either LESSCHARSET=IBM-1047
LC_CTYPE=en_US in your environment.
koi8-r Selects a Russian character set.
next Selects a character set appropriate for NeXT computers.
utf-8 Selects the UTF-8 encoding of the ISO 10646 character set. UTF-8 is special in that it supports multi-byte
characters in the input file. It is the only character set that supports multi-byte characters.
windows
Selects a character set appropriate for Microsoft Windows (cp 1251).
In rare cases, it may be desired to tailor less to use a character set other than the ones definable by LESSCHARSET.
In this case, the environment variable LESSCHARDEF can be used to define a character set. It should be set to a string
where each character in the string represents one character in the character set. The character "." is used for a normal character, "c" for control, and "b" for binary. A decimal number may be used for repetition. For example,
"bccc4b." would mean character 0 is binary, 1, 2 and 3 are control, 4, 5, 6 and 7 are binary, and 8 is normal. All
characters after the last are taken to be the same as the last, so characters 9 through 255 would be normal. (This is
an example, and does not necessarily represent any real character set.)
This table shows the value of LESSCHARDEF which is equivalent to each of the possible values for LESSCHARSET:
ascii 8bcccbcc18b95.b
dos 8bcccbcc12bc5b95.b.
ebcdic 5bc6bcc7bcc41b.9b7.9b5.b..8b6.10b6.b9.7b
9.8b8.17b3.3b9.7b9.8b8.6b10.b.b.b.
IBM-1047 4cbcbc3b9cbccbccbb4c6bcc5b3cbbc4bc4bccbc
191.b
iso8859 8bcccbcc18b95.33b.
koi8-r 8bcccbcc18b95.b128.
latin1 8bcccbcc18b95.33b.
next 8bcccbcc18b95.bb125.bb
If neither LESSCHARSET nor LESSCHARDEF is set, but any of the strings "UTF-8", "UTF8", "utf-8"
"utf8" is found in
the LC_ALL, LC_TYPE
LANG environment variables, then the default character set is utf-8.
If that string is not found, but your system supports the setlocale interface, less will use setlocale to determine the
character set. setlocale is controlled by setting the LANG
LC_CTYPE environment variables.
Finally, if the setlocale interface is also not available, the default character set is latin1.
Control and binary characters are displayed in standout (reverse video). Each such character is displayed in caret
notation if possible (e.g. ^A for control-A). Caret notation is used only if inverting the 0100 bit results in a normal printable character. Otherwise, the character is displayed as a hex number in angle brackets. This format can be
changed by setting the LESSBINFMT environment variable. LESSBINFMT may begin with a "*" and one character to select
the display attribute: "*k" is blinking, "*d" is bold, "*u" is underlined, "*s" is standout, and "*n" is normal. If
LESSBINFMT does not begin with a "*", normal attribute is assumed. The remainder of LESSBINFMT is a string which may
include one printf-style escape sequence (a % followed by x, X, o, d, etc.). For example, if LESSBINFMT is "*u[%x]",
binary characters are displayed in underlined hexadecimal surrounded by brackets. The default if no LESSBINFMT is
specified is "*s<%X>". The default if no LESSBINFMT is specified is "*s<%02X>". Warning: the result of expanding the
character via LESSBINFMT must be less than 31 characters.
When the character set is utf-8, the LESSUTFBINFMT environment variable acts similarly to LESSBINFMT but it applies to
Unicode code points that were successfully decoded but are unsuitable for display (e.g., unassigned code points). Its
default value is "<U+%04lX>". Note that LESSUTFBINFMT and LESSBINFMT share their display attribute setting ("*x") so
specifying one will affect both; LESSUTFBINFMT is read after LESSBINFMT so its setting, if any, will have priority.
Problematic octets in a UTF-8 file (octets of a truncated sequence, octets of a complete but non-shortest form
sequence, illegal octets, and stray trailing octets) are displayed individually using LESSBINFMT so as to facilitate
diagnostic of how the UTF-8 file is ill-formed.
PROMPTS
The -P option allows you to tailor the prompt to your preference. The string given to the -P option replaces the specified prompt string. Certain characters in the string are interpreted specially. The prompt mechanism is rather complicated to provide flexibility, but the ordinary user need not understand the details of constructing personalized
prompt strings.
A percent sign followed by a single character is expanded according to what the following character is:
%bX Replaced by the byte offset into the current input file. The b is followed by a single character (shown as X
above) which specifies the line whose byte offset is to be used. If the character is a "t", the byte offset of
the top line in the display is used, an "m" means use the middle line, a "b" means use the bottom line, a "B"
means use the line just after the bottom line, and a "j" means use the "target" line, as specified by the -j
option.
%B Replaced by the size of the current input file.
%c Replaced by the column number of the text appearing in the first column of the screen.
%dX Replaced by the page number of a line in the input file. The line to be used is determined by the X, as with
the %b option.
%D Replaced by the number of pages in the input file,
equivalently, the page number of the last line in the
input file.
%E Replaced by the name of the editor (from the VISUAL environment variable,
the EDITOR environment variable if
VISUAL is not defined). See the discussion of the LESSEDIT feature below.
%f Replaced by the name of the current input file.
%i Replaced by the index of the current file in the list of input files.
%lX Replaced by the line number of a line in the input file. The line to be used is determined by the X, as with
the %b option.
%L Replaced by the line number of the last line in the input file.
%m Replaced by the total number of input files.
%pX Replaced by the percent into the current input file, based on byte offsets. The line used is determined by the
X as with the %b option.
%PX Replaced by the percent into the current input file, based on line numbers. The line used is determined by the
X as with the %b option.
%s Same as %B.
%t Causes any trailing spaces to be removed. Usually used at the end of the string, but may appear anywhere.
%x Replaced by the name of the next input file in the list.
If any item is unknown (for example, the file size if input is a pipe), a question mark is printed instead.
The format of the prompt string can be changed depending on certain conditions. A question mark followed by a single
character acts like an "IF": depending on the following character, a condition is evaluated. If the condition is true,
any characters following the question mark and condition character, up to a period, are included in the prompt. If the
condition is false, such characters are not included. A colon appearing between the question mark and the period can
be used to establish an "ELSE": any characters between the colon and the period are included in the string if and only
if the IF condition is false. Condition characters (which follow a question mark) may be:
?a True if any characters have been included in the prompt so far.
?bX True if the byte offset of the specified line is known.
?B True if the size of current input file is known.
?c True if the text is horizontally shifted (%c is not zero).
?dX True if the page number of the specified line is known.
?e True if at end-of-file.
?f True if there is an input filename (that is, if input is not a pipe).
?lX True if the line number of the specified line is known.
?L True if the line number of the last line in the file is known.
?m True if there is more than one input file.
?n True if this is the first prompt in a new input file.
?pX True if the percent into the current input file, based on byte offsets, of the specified line is known.
?PX True if the percent into the current input file, based on line numbers, of the specified line is known.
?s Same as "?B".
?x True if there is a next input file (that is, if the current input file is not the last one).
Any characters other than the special ones (question mark, colon, period, percent, and backslash) become literally part
of the prompt. Any of the special characters may be included in the prompt literally by preceding it with a backslash.
Some examples:
?f%f:Standard input.
This prompt prints the filename, if known; otherwise the string "Standard input".
?f%f .?ltLine %lt:?pt%pt\%:?btByte %bt:-...
This prompt would print the filename, if known. The filename is followed by the line number, if known, otherwise the
percent if known, otherwise the byte offset if known. Otherwise, a dash is printed. Notice how each question mark has
a matching period, and how the % after the %pt is included literally by escaping it with a backslash.
?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x..%t
This prints the filename if this is the first prompt in a file, followed by the "file n of N" message if there is more
than one input file. Then, if we are at end-of-file, the string "(END)" is printed followed by the name of the next
file, if there is one. Finally, any trailing spaces are truncated. This is the default prompt. For reference, here
are the defaults for the other two prompts (-m and -M respectively). Each is broken into two lines here for readability only.
?n?f%f .?m(file %i of %m) ..?e(END) ?x- Next\: %x.:
?pB%pB\%:byte %bB?s/%s...%t
?f%f .?n?m(file %i of %m) ..?ltlines %lt-%lb?L/%L. :
byte %bB?s/%s. .?e(END) ?x- Next\: %x.:?pB%pB\%..%t
And here is the default message produced by the = command:
?f%f .?m(file %i of %m) .?ltlines %lt-%lb?L/%L. .
byte %bB?s/%s. ?e(END) :?pB%pB\%..%t
The prompt expansion features are also used for another purpose: if an environment variable LESSEDIT is defined, it is
used as the command to be executed when the v command is invoked. The LESSEDIT string is expanded in the same way as
the prompt strings. The default value for LESSEDIT is:
%E ?lm+%lm. %f
Note that this expands to the editor name, followed by a + and the line number, followed by the file name. If your
editor does not accept the "+linenumber" syntax,
has other differences in invocation syntax, the LESSEDIT variable
can be changed to modify this default.
SECURITY
When the environment variable LESSSECURE is set to 1, less runs in a "secure" mode. This means these features are disabled:
! the shell command
| the pipe command
:e the examine command.
v the editing command
s -o log files
-k use of lesskey files
-t use of tags files
metacharacters in filenames, such as *
filename completion (TAB, ^L)
Less can also be compiled to be permanently in "secure" mode.
Compatibility with more
Allows backward as well as forward movement.
Uses termcap (terminfo), so it can run on a variety of terminals.
Limited support for hardcopy terminals, lines which should be printed at
the top of the screen are prefixed with a caret.
If $LESS_IS_MORE is set to 1, or` if invoked via a link named "more", less
behaves (mostly) in conformance with the POSIX "more"
-e If not set, if the -E option were set.
If set, as if the -e and -F options were set.
-m not set, the medium prompt is used, and it is prefixed with the
string "--More--".
If set, the short prompt is used.
-n acts like -z .
The parameter to -p is taken to be a less command rather than a search pattern.
$LESS is ignored, $MORE is used
ENVIRONMENT VARIABLES
Environment variables may also be specified in lesskey which takes precedence.
which take precedence over variables defined in the system-wide lesskey
$COLUMNS
Sets the number of columns on the screen. Takes precedence over the number of columns specified by the TERM
variable. (But if you have a windowing system which supports TIOCGWINSZ
WIOCGETD, the window system's idea
of the screen size takes precedence over the LINES and COLUMNS environment variables.)
$EDITOR The name of the editor (used for the v command).
$HOME Name of the user's home directory (used to find a lesskey file on Unix and OS/2 systems).
$HOMEDRIVE, $HOMEPATH
Concatenation of the HOMEDRIVE and HOMEPATH environment variables is the name of the user's home directory if
the HOME variable is not set (only in the Windows version).
$INIT Name of the user's init directory (used to find a lesskey file on OS/2 systems).
$LANG Language for determining the character set.
$LC_CTYPE
Language for determining the character set.
$LESS Options which are passed to less automatically.
$LESSANSIENDCHARS
Characters which may end an ANSI color escape sequence (default "m").
$LESSANSIMIDCHARS
Characters which may appear between the ␛ character and the end character in an ANSI color escape sequence
(default "0123456789;[?!"'#%()*+ ".
$LESSBINFMT
Format for displaying non-printable, non-control characters.
$LESSCHARDEF
Defines a character set.
$LESSCHARSET
Selects a predefined character set.
$LESSCLOSE
Command line to invoke the (optional) input-postprocessor.
$LESSECHO
Name of the lessecho program (default "lessecho"). The lessecho program is needed to expand metacharacters,
such as * and ?, in filenames on Unix systems.
$LESSEDIT
Editor prototype string (used for the v command). See discussion under PROMPTS.
$LESSGLOBALTAGS
Name of the command used by the -t option to find global tags. Normally should be set to "global" if your system has the global (1) command. If not set, global tags are not used.
$LESSHISTFILE
Name of the history file used to remember search commands and shell commands between invocations of less. If
set to "-"
"/dev/null", a history file is not used. The default is "$HOME/.lesshst" on Unix systems,
"$HOME/_lesshst" on DOS and Windows systems,
"$HOME/lesshst.ini"
"$INIT/lesshst.ini" on OS/2 systems.
$LESSHISTSIZE
The maximum number of commands to save in the history file. The default is 100.
$LESSKEY
Name of the default lesskey(1) file.
$LESSKEY_SYSTEM Name of the default system-wide lesskey(1) file.
$LESSMETACHARS List of characters which are considered "metacharacters" by the shell.
$LESSMETAESCAPE Prefix which less will add before each metacharacter in a command sent to the shell. If LESSMETA␛APE is an
empty string, commands containing metacharacters will not be passed to the shell.
$LESSOPEN Command line to invoke the (optional) input-preprocessor.
$LESSSECURE Runs less in "secure" mode. See discussion under SECURITY.
$LESSSEPARATOR String to be appended to a directory name in filename completion.
$LESSUTFBINFMT Format for displaying non-printable Unicode code points.
$LESS_IS_MORE Emulate the more (1) command.
$LINES Sets the number of lines on the screen. Takes precedence over the number of lines specified by the TERM variable. (But if you have a windowing system which supports TIOCGWINSZ
WIOCGETD, the window system's idea of
the screen size takes precedence over the LINES and COLUMNS environment variables.)
$PATH User's search path (used to find a lesskey file on MS-DOS and OS/2 systems).
$SHELL The shell used to execute the ! command, as well as to expand filenames.
$TERM The type of terminal on which less is being run.
$VISUAL The name of the editor (used for the v command).
COPYRIGHT Copyright (C) 1984-2007 Mark Nudelman AUTHOR Mark Nudelman