less - opposite of more
less -?
less --help
less -V
less --version
less [-[+]aBcCdeEfgGiImMnNqQrsSuUVwX]
[-b bufs] [-h lines] [-j line] [-k keyfile]
[-{oO} logfile] [-p pattern] [-P prompt] [-t tag]
[-T tagsfile] [-x tab] [-y lines] [-[z] lines]
[+[+]cmd] [--] [filename]...
(See the OPTIONS section for alternate option syntax with
long option names.)
Less is a program similar to more (1), but which allows backward movement in the file as well as forward movement. Also, less does not have to read the entire input file before starting, so with large input files it starts up faster than text editors like vi (1). Less uses termcap (or terminfo on some systems), so it can run on a variety of terminals. There is even limited support for hardcopy terminals. (On a hardcopy terminal, lines which should be printed at the top of the screen are prefixed with a caret.)
Commands are based on both more and vi. Commands may be preceded by a decimal number, called N in the descriptions below. The number is used by some commands, as indicated.
In the following descriptions, ^X means control-X. ESC stands for the ESCAPE key; for example ESC-v means the two character sequence ESCAPE", then v".
h or H Help: display a summary of these commands. If you forget all the other commands, remember this one.
SPACE or ^V or f or ^F
Scroll forward N lines, default one window (see
option -z below). If N is more than the screen
size, only the final screenful is displayed. Warning:
some systems use ^V as a special literalization
character.
RETURN or ^N or e or ^E or j or ^J Scroll forward N lines, default 1. The entire N lines are displayed, even if N is more than the screen size.
d or ^D
Scroll forward N lines, default one half of the
screen size. If N is specified, it becomes the new
default for subsequent d and u commands.
b or ^B or ESC-v
Scroll backward N lines, default one window (see
option -z below). If N is more than the screen
size, only the final screenful is displayed.
y or ^Y or ^P or k or ^K
Scroll backward N lines, default 1. The entire N
lines are displayed, even if N is more than the
screen size. Warning: some systems use ^Y as a
special job control character.
u or ^U
Scroll backward N lines, default one half of the
screen size. If N is specified, it becomes the new
default for subsequent d and u commands.
ESC-) or RIGHTARROW
Scroll horizontally right N characters, default 8.
This behaves best if you also set the -S option
(chop lines). Note that if you wish to enter a
number N, you must use ESC-), not RIGHTARROW,
because the arrow is taken to be a line editing
command (see the LINE EDITING section).
ESC-( or LEFTARROW
Scroll horizontally left N characters, default 8.
r or ^R or ^L
Repaint the screen.
g or < or ESC-<
Go to line N in the file, default 1 (beginning of
file). (Warning: this may be slow if N is large.)
G or > or ESC->
Go to line N in the file, default the end of the
file. (Warning: this may be slow if N is large, or
if N is not specified and standard input, rather
than a file, is being read.)
p or % Go to a position N percent into the file. N should be between 0 and 100.
ESC-^F Followed by two characters, acts like {, but uses the two characters as open and close brackets, respectively. For example, ESC ^F < > could be used to go forward to the > which matches the < in the top displayed line.
ESC-^B Followed by two characters, acts like }, but uses the two characters as open and close brackets, respectively. For example, ESC ^B < > could be used to go backward to the < which matches the > in the bottom displayed line.
/pattern
Search forward in the file for the N-th line containing
the pattern. N defaults to 1. The pattern
is a regular expression, as recognized by ed. The
search starts at the second line displayed (but see
the -a and -j options, which change this).
Certain characters are special if entered at the beginning of the pattern; they modify the type of search rather than become part of the pattern:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the
search reaches the END of the current file
without finding a match, the search continues
in the next file in the command line
list.
^F or @
Begin the search at the first line of the
FIRST file in the command line list, regardless
of what is currently displayed on the
screen or the settings of the -a or -j
options.
?pattern
Search backward in the file for the N-th line
containing the pattern. The search starts at the
line immediately before the top line displayed.
Certain characters are special as in the / command:
^N or !
Search for lines which do NOT match the pattern.
^E or *
Search multiple files. That is, if the
search reaches the beginning of the current
file without finding a match, the search
continues in the previous file in the command
line list.
^F or @
Begin the search at the last line of the
last file in the command line list, regardless
of what is currently displayed on the
screen or the settings of the -a or -j
options.
ESC-/pattern
Same as /*".
ESC-?pattern
Same as ?*".
ESC-n Repeat previous search, but crossing file boundaries. The effect is as if the previous search were modified by *.
ESC-N Repeat previous search, but in the reverse direction and crossing file boundaries.
ESC-u Undo search highlighting. Turn off highlighting of strings matching the current search pattern. If highlighting is already off because of a previous ESC-u command, turn highlighting back on. Any search command will also turn highlighting back on. (Highlighting can also be disabled by toggling the -G option; in that case search commands do not turn highlighting back on.)
:e [filename]
Examine a new file. If the filename is missing,
the current file (see the :n and :p commands
below) from the list of files in the command line
is re-examined. A percent sign (%) in the filename
is replaced by the name of the current file. A
pound sign (#) is replaced by the name of the previously
examined file. However, two consecutive
percent signs are simply replaced with a single
percent sign. This allows you to enter a filename
that contains a percent sign in the name. Similarly,
two consecutive pound signs are replaced
with a single pound sign. The filename is inserted
into the command line list of files so that it can
be seen by subsequent :n and :p commands. If the
filename consists of several files, they are all
inserted into the list of files and the first one
is examined. If the filename contains one or more
spaces, the entire filename should be enclosed in
double quotes (also see the - option).
^X^V or E
Same as :e. Warning: some systems use ^V as a special
literalization character. On such systems,
you may not be able to use ^V.
= or ^G or :f
Prints some information about the file being
viewed, including its name and the line number and
byte offset of the bottom line being displayed. If
possible, it also prints the length of the file,
the number of lines in the file and the percent of
the file above the last displayed line.
q or Q or :q or :Q or ZZ
Exits less.
The following four commands may or may not be valid, depending on your particular installation.
! shell-command
Invokes a shell to run the shell-command given. A
percent sign (%) in the command is replaced by the
name of the current file. A pound sign (#) is
replaced by the name of the previously examined
file. !! repeats the last shell command. !"
with no shell command simply invokes a shell. On
Unix systems, the shell is taken from the environment
variable SHELL, or defaults to sh". On MSDOS
and OS/2 systems, the shell is the normal command
processor.
| <m> shell-command
<m> represents any mark letter. Pipes a section of
the input file to the given shell command. The
section of the file to be piped is between the
first line on the current screen and the position
marked by the letter. <m> may also be ^ or $ to
indicate beginning or end of file respectively. If
<m> is . or newline, the current screen is piped.
s filename
Save the input to a file. This only works if the
input is a pipe, not an ordinary file.
Command line options are described below. Most options may be changed while less is running, via the - command.
Most options may be given in one of two forms: either a dash followed by a single letter, or two dashes followed by a long option name. A long option name may be abbreviated as long as the abbreviation is unambiguous. For example, --quit-at-eof may be abbreviated --quit, but not --qui, since both --quit-at-eof and --quiet begin with --qui. Some long option names are in uppercase, such as --QUIT-AT-EOF, as distinct from --quit-at-eof. Such option names need only have their first letter capitalized; the remainder of the name may be in either case. For example, --Quit-at-eof is equivalent to --QUIT-AT-EOF.
Options are also taken from the environment variable LESS". For example, to avoid typing less -options ..." each time less is invoked, you might tell csh:
setenv LESS -options"
or if you use sh:
LESS="-options"; export LESS
On MS-DOS, you don't need the quotes, but you should replace any percent signs in the options string by double percent signs.
The environment variable is parsed before the command line, so command line options override the LESS environment variable. If an option appears in the LESS variable, it can be reset to its default value on the command line by beginning the command line option with -+".
For options like -P or -D which take a following string, a dollar sign ($) must be used to signal the end of the string. For example, to set two -D options on MS-DOS, you must have a dollar sign between them, like this:
LESS="-Dn9.1$-Ds4.1"
If no log file has been specified, the -o and -O options can be used from within less to specify a log file. Without a file name, they will simply report the name of the log file. The s command is equivalent to specifying -o from within less.
By default, if neither -u nor -U is given, backspaces which appear adjacent to an underscore character are treated specially: the underlined text is displayed using the terminal's hardware underlining capability. Also, backspaces which appear between two identical characters are treated specially: the overstruck text is printed using the terminal's hardware boldface capability. Other backspaces are deleted, along with the preceding character. Carriage returns immediately followed by a newline are deleted. other carriage returns are handled as specified by the -r option. Text which is overstruck or underlined can be searched for if neither -u nor -U is in effect.
remainder of that option is taken to be an initial command to less. For example, +G tells less to start at the end of the file rather than the beginning, and +/xyz tells it to start at the first occurrence of xyz in the file. As a special case, +<number> acts like +<number>g; that is, it starts the display at the specified line number (however, see the caveat under the g command above). If the option starts with ++, the initial command applies to every file being viewed, not just the first one. The + command described previously may also be used to set (or change) an initial command for every file.
When entering command line at the bottom of the screen (for example, a filename for the :e command, or 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. (The bracketed forms do not work in the MS-DOS version.) Any of these special keys may be entered literally by preceding it with the literal character, either ^V or ^A. A backslash itself may also be entered literally by entering two backslashes.
LEFTARROW [ ESC-h ]
Move the cursor one space to the left.
RIGHTARROW [ ESC-l ]
Move the cursor one space to the right.
^LEFTARROW [ ESC-b or ESC-LEFTARROW ]
(That is, CONTROL and LEFTARROW simultaneously.)
Move the cursor one word to the left.
^RIGHTARROW [ ESC-w or ESC-RIGHTARROW ] (That is, CONTROL and RIGHTARROW simultaneously.) Move the cursor one word to the right.
DELETE or [ ESC-x ]
Delete the character under the cursor.
^DELETE [ ESC-X or ESC-DELETE ]
(That is, CONTROL and DELETE simultaneously.)
Delete the word under the cursor.
UPARROW [ ESC-k ]
Retrieve the previous command line.
DOWNARROW [ ESC-j ]
Retrieve the next command line.
^U (Unix) or ESC (MS-DOS)
Delete the entire command line, or 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.
You may 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 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.
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 postprocessor. 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 -c $1 >/tmp/less.$$ 2>/dev/null
if [ -s /tmp/less.$$ ]; 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 -".
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 The default character set. 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 the ISO 8859/1 character set. latin-1 is
the same as ASCII, except characters between 161
and 255 are treated as normal characters.
latin1 Same as iso8859.
ebcdic Selects an EBCDIC character set.
koi8-r Selects a Russian character set.
next Selects a character set appropriate for NeXT computers.
In special 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:
If neither LESSCHARSET nor LESSCHARDEF is set, but your system supports the setlocale interface, less will use setlocale to determine the character set. setlocale is controlled by setting the LANG or LC_CTYPE environment variables.
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 -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:
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:
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) ..?ltline %lt?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) .?ltline %lt?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, or has other differences in invocation syntax, the LESSEDIT variable can be changed to modify this default.
When the environment variable LESSSECURE is set to 1, less runs in a secure mode. This means these features are disabled:
s -o log files
metacharacters in filenames, such as *
filename completion (TAB, ^L)
Less can also be compiled to be permanently in secure" mode.
Environment variables may be specified either in the system environment as usual, or in a lesskey (1) file.
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 systems).
INIT Name of the user's init directory (used to find a lesskey file on OS/2 systems).
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 or 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.
VISUAL The name of the editor (used for the v command).
The = command and prompts (unless changed by -P) report the line number of the line at the top of the screen, but the byte and percent of the line at the bottom of the screen.
If the :e command is used to name more than one file, and one of the named files has been viewed previously, the new files may be entered into the list in an unexpected order.
On certain older terminals (the so-called magic cookie" terminals), search highlighting will cause an erroneous display. On such terminals, search highlighting is disabled by default to avoid possible problems.
In certain cases, when search highlighting is enabled and a search pattern begins with a ^, more text than the matching string may be highlighted. (This problem does not occur when less is compiled to use the POSIX regular expression package.)
On some systems, setlocale claims that ASCII characters 0 thru 31 are control characters rather than binary characters. This causes less to treat some binary files as ordinary, non-binary files. To workaround this problem, set the environment variable LESSCHARSET to ascii (or whatever character set is appropriate).
The MS-DOS and Windows versions sometimes display incorrect highlighting when lines are longer than the screen width.
See http://www.flash.net/~marknu/less for the latest list of known bugs in this version of less.
Copyright (C) 1999 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 the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version.
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.
You should have received a copy of the GNU General Public License along with less; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
Mark Nudelman <marknu@flash.net>
Send bug reports or comments to the above address or to
bug-less@gnu.org.