less
SYNOPSIS
less -?
less --help
less -V
less --version
less [-[+]aABcCdeEfFgGiIJLmMnNqQrRsSuUVwWX~]
[-b space] [-h lines] [-j line] [-k keyfile]
[-K character set] [-{oO} logfile]
[-p pattern] [-P prompt] [-t tag]"
[-T tagsfile] [-x tab,...] [-y lines] [-[z] lines]
[-# shift] [+[+]cmd] [--] [filename]...
(See the OPTIONS section for alternate option syntax with
long option names.)
DESCRIPTION
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.
COMMANDS
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. Warn
ing: some systems use ^V as a special literaliza
tion character.
z Like SPACE, but if N is specified, it becomes the
new window size.
ESC-SPACE
Like SPACE, but scrolls a full screenful, even if
option -z below). If N is more than the screen
size, only the final screenful is displayed.
w Like ESC-v, but if N is specified, it becomes the
new window size.
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
half the screen width (see the -# option). If a
number N is specified, it becomes the default for
future RIGHTARROW and LEFTARROW commands. While
the text is scrolled, it acts as though the -S
option (chop lines) were in effect.
ESC-( or LEFTARROW
Scroll horizontally left N characters, default half
the screen width (see the -# option). If a number
N is specified, it becomes the default for future
RIGHTARROW and LEFTARROW commands.
r or ^R or ^L
Repaint the screen.
R Repaint the screen, discarding any buffered input.
Useful if the file is changing while it is being
viewed.
F Scroll forward, and keep trying to read when the
end of file is reached. Normally this command
would be used when already at the end of the file.
It is a way to monitor the tail of a file which is
growing while it is being viewed. (The behavior is
similar to the "tail -f" command.)
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 a right curly bracket appears in the bottom line
displayed on the screen, the } command will go to
the matching left curly bracket. The matching left
curly bracket is positioned on the top line of the
screen. If there is more than one right curly
bracket on the top line, a number N may be used to
specify the N-th bracket on the line.
( Like {, but applies to parentheses rather than
curly brackets.
) Like }, but applies to parentheses rather than
curly brackets.
[ Like {, but applies to square brackets rather than
curly brackets.
] Like }, but applies to square brackets rather than
curly brackets.
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.
m Followed by any lowercase letter, marks the current
position with that letter.
' (Single quote.) Followed by any lowercase letter,
returns to the position which was previously marked
with that letter. Followed by another single
quote, returns to the position at which the last
"large" movement command was executed. Followed by
a ^ or $, jumps to the beginning or end of the file
respectively. Marks are preserved when a new file
is examined, so the ' command can be used to switch
between input files.
^X^X Same as single quote.
/pattern
Search forward in the file for the N-th line con
taining 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
ues 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, regard
less of what is currently displayed on the
screen or the settings of the -a or -j
options.
^K Highlight any text which matches the pattern
on the current screen, but don't move to the
first match (KEEP current position).
^R Don't interpret regular expression metachar
acters; that is, do a simple textual compar
ison.
?pattern
Search backward in the file for the N-th line con
taining 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 pat
tern.
^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 com
mand line list.
^F or @
Begin the search at the last line of the
last file in the command line list, regard
less of what is currently displayed on the
screen or the settings of the -a or -j
options.
^K As in forward searches.
^R As in forward searches.
ESC-/pattern
Same as "/*".
ESC-?pattern
Same as "?*".
ESC-n Repeat previous search, but crossing file bound
aries. The effect is as if the previous search
were modified by *.
ESC-N Repeat previous search, but in the reverse direc
tion 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 pre
viously 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. Simi
larly, 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 spe
cial literalization character. On such systems,
you may not be able to use ^V.
:n Examine the next file (from the list of files given
in the command line). If a number N is specified,
the N-th next file is examined.
:p Examine the previous file in the command line list.
If a number N is specified, the N-th previous file
is examined.
:x Examine the first file in the command line list.
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.
@ Rotate the code recognition method of the current
file. Enhanced less has 7 methods for recognition,
default (which is chosen by the JLESSCHARSET envi
ronment variable), japanese, ujis, sjis, iso8,
noconv and none.
- Followed by one of the command line option letters
(see OPTIONS below), this will change the setting
of that option and print a message describing the
new setting. If a ^P (CONTROL-P) is entered imme
diately after the dash, the setting of the option
is changed but no message is printed. If the
option letter has a numeric value (such as -b or
-h), or a string value (such as -P or -t), a new
value may be entered after the option letter. If
no new value is entered, a message describing the
current setting is printed and nothing is changed.
-- Like the - command, but takes a long option name
(see OPTIONS below) rather than a single option
letter. You must press RETURN after typing the
option name. A ^P immediately after the second
dash suppresses printing of a message describing
the new setting, as in the - command.
-+ Followed by one of the command line option letters
this will reset the option to its default setting
and print a message describing the new setting.
(The "-+X" command does the same thing as "-+X" on
the command line.) This does not work for string-
valued options.
--+ Like the -+ command, but takes a long option name
rather than a single option letter.
-! Followed by one of the command line option letters,
this will reset the option to the "opposite" of its
default setting and print a message describing the
new setting. This does not work for numeric or
string-valued options.
--! Like the -! command, but takes a long option name
rather than a single option letter.
_ (Underscore.) Followed by one of the command line
option letters, this will print a message describ
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.
v Invokes an editor to edit the current file being
viewed. The editor is taken from the environment
variable VISUAL if defined, or EDITOR if VISUAL is
not defined, or defaults to "vi" if neither VISUAL
nor EDITOR is defined. See also the discussion of
LESSEDIT under the section on PROMPTS below.
! 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 environ
ment variable SHELL, or defaults to "sh". On MS-
DOS and OS/2 systems, the shell is the normal com
mand 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.
OPTIONS
Command line options are described below. Most options
may be changed while less is running, via the "-" command.
Options are also taken from the environment variable
"LESS" and "JLESS".
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 abbrevi
ated as long as the abbreviation is unambiguous. For
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 and JLESS
environment variables. If an option appears in the LESS
and JLESS variables, 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"
-? or --help
This option displays a summary of the commands
accepted by less (the same as the h command).
(Depending on how your shell interprets the ques
tion mark, it may be necessary to quote the ques
tion mark, thus: "-\?".)
-a or --search-skip-screen
Causes searches to start after the last line dis
played on the screen, thus skipping all lines dis
played on the screen. By default, searches start
at the second line on the screen (or after the last
found line; see the -j option).
-A or --mouse-support
Causes less to process mouse actions itself. Cur
rently it works only in xterm. The inspiration
comes from vim-6.0.
Cut&Paste function works only internally by
default. To access X selection you must hold SHIFT
key to process the mouse actions by xterm. Or you
can install xselection utility by which less is
able to access X selection itself.
Also scrolling by mouse wheel button is supported.
You must map wheel mouse action on the 4th and 5th
mouse button. This is done in XF86Config in Section
"InputDevice" by option:
By default, when data is read from a pipe, buffers
are allocated automatically as needed. If a large
amount of data is read from the pipe, this can
cause a large amount of memory to be allocated.
The -B option disables this automatic allocation of
buffers for pipes, so that only 64K (or the amount
of space specified by the -b option) is used for
the pipe. Warning: use of -B can result in erro
neous display, since only the most recently viewed
part of the file is kept in memory; any earlier
data is lost.
-c or --clear-screen
Causes full screen repaints to be painted from the
top line down. By default, full screen repaints
are done by scrolling from the bottom of the
screen.
-C or --CLEAR-SCREEN
The -C option is like -c, but the screen is cleared
before it is repainted.
-d or --dumb
The -d option suppresses the error message normally
displayed if the terminal is dumb; that is, lacks
some important capability, such as the ability to
clear the screen or scroll backward. The -d option
does not otherwise change the behavior of less on a
dumb terminal.
-Dxcolor or --color=xcolor
[MS-DOS only] Sets the color of the text displayed.
x is a single character which selects the type of
text whose color is being set: n=normal, s=stand
out, d=bold, u=underlined, k=blink. color is a
pair of numbers separated by a period. The first
number selects the foreground color and the second
selects the background color of the text. A single
number N is the same as N.0.
-e or --quit-at-eof
Causes less to automatically exit the second time
it reaches end-of-file. By default, the only way
to exit less is via the "q" command.
-E or --QUIT-AT-EOF
Causes less to automatically exit the first time it
reaches end-of-file.
-f or --force
Forces non-regular files to be opened. (A non-reg
ular file is a directory or a device special file.)
than the default.
-G or --HILITE-SEARCH
The -G option suppresses all highlighting of
strings found by search commands.
-hn or ---max-back-scroll=n
Specifies a maximum number of lines to scroll back
ward. If it is necessary to scroll backward more
than n lines, the screen is repainted in a forward
direction instead. (If the terminal does not have
the ability to scroll backward, -h0 is implied.)
-i or --ignore-case
Causes searches to ignore case; that is, uppercase
and lowercase are considered identical. This
option is ignored if any uppercase letters appear
in the search pattern; in other words, if a pattern
contains uppercase letters, then that search does
not ignore case.
-I or --IGNORE-CASE
Like -i, but searches ignore case even if the pat
tern contains uppercase letters.
-jn or --jump-target=n
Specifies a line on the screen where the "target"
line is to be positioned. A target line is the
object of a text search, tag search, jump to a line
number, jump to a file percentage, or jump to a
marked position. The screen line is specified by a
number: the top line on the screen is 1, the next
is 2, and so on. The number may be negative to
specify a line relative to the bottom of the
screen: the bottom line on the screen is -1, the
second to the bottom is -2, and so on. If the -j
option is used, searches begin at the line immedi
ately after the target line. For example, if "-j4"
is used, the target line is the fourth line on the
screen, so searches begin at the fifth line on the
screen.
-J or --status-column
Displays a status column at the left edge of the
screen. The status column shows the lines that
matched the current search. The status column is
also used if the -w or -W option is in effect.
-kfilename or --lesskey-file=filename
Causes less to open and interpret the named file as
a lesskey (1) file. Multiple -k options may be
specified. If the LESSKEY or LESSKEY_SYSTEM envi
currently open.
-m or --long-prompt
Causes less to prompt verbosely (like more), with
the percent into the file. By default, less
prompts with a colon.
-M or --LONG-PROMPT
Causes less to prompt even more verbosely than
more.
-n or --line-numbers
Suppresses line numbers. The default (to use line
numbers) may cause less to run more slowly in some
cases, especially with a very large input file.
Suppressing line numbers with the -n option will
avoid this problem. Using line numbers means: the
line number will be displayed in the verbose prompt
and in the = command, and the v command will pass
the current line number to the editor (see also the
discussion of LESSEDIT in PROMPTS below).
-N or --LINE-NUMBERS
Causes a line number to be displayed at the begin
ning of each line in the display.
-ofilename or --log-file=filename
Causes less to copy its input to the named file as
it is being viewed. This applies only when the
input file is a pipe, not an ordinary file. If the
file already exists, less will ask for confirmation
before overwriting it.
-Ofilename or --LOG-FILE=filename
The -O option is like -o, but it will overwrite an
existing file without asking for confirmation.
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.
-ppattern or --pattern=pattern
The -p option on the command line is equivalent to
specifying +/pattern; that is, it tells less to
start at the first occurrence of pattern in the
file.
-Pprompt or --prompt=prompt
Provides a way to tailor the three prompt styles to
your own preference. This option would normally be
-q or --quiet or --silent
Causes moderately "quiet" operation: the terminal
bell is not rung if an attempt is made to scroll
past the end of the file or before the beginning of
the file. If the terminal has a "visual bell", it
is used instead. The bell will be rung on certain
other errors, such as typing an invalid character.
The default is to ring the terminal bell in all
such cases.
-Q or --QUIET or --SILENT
Causes totally "quiet" operation: the terminal bell
is never rung.
-r or --raw-control-chars
Causes "raw" control characters to be displayed.
The default is to display control characters using
the caret notation; for example, a control-A (octal
001) is displayed as "^A". Warning: when the -r
option is used, less cannot keep track of the
actual appearance of the screen (since this depends
on how the screen responds to each type of control
character). Thus, various display problems may
result, such as long lines being split in the wrong
place.
-R or --RAW-CONTROL-CHARS
Like -r, but tries to keep track of the screen
appearance where possible. This works only if the
input consists of normal text and possibly some
ANSI "color" escape sequences, which are sequences
of the form:
ESC [ ... m
where the "..." is zero or more characters other
than "m". For the purpose of keeping track of
screen appearance, all control characters and all
ANSI color escape sequences are assumed to not move
the cursor. You can make less think that charac
ters other than "m" can end ANSI color escape
sequences by setting the environment variable
LESSANSIENDCHARS to the list of characters which
can end a color escape sequence.
-s or --squeeze-blank-lines
Causes consecutive blank lines to be squeezed into
a single blank line. This is useful when viewing
nroff output.
-S or --chop-long-lines
variable LESSGLOBALTAGS is set, it is taken to be
the name of a command compatible with global (1),
and that command is executed to find the tag. (See
http://www.gnu.org/software/global/global.html).
The -t option may also be specified from within
less (using the - command) as a way of examining a
new file. The command ":t" is equivalent to speci
fying -t from within less.
-Ttagsfile or --tag-file=tagsfile
Specifies a tags file to be used instead of "tags".
-u or --underline-special
Causes backspaces and carriage returns to be
treated as printable characters; that is, they are
sent to the terminal when they appear in the input.
-U or --UNDERLINE-SPECIAL
Causes backspaces, tabs and carriage returns to be
treated as control characters; that is, they are
handled as specified by the -r option.
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.
-V or --version
Displays the version number of less.
-w or --hilite-unread
Temporarily highlights the first "new" line after a
forward movement of a full page. The first "new"
line is the line immediately following the line
previously at the bottom of the screen. Also high
lights the target line after a g or p command. The
highlight is removed at the next command which
causes movement. The entire line is highlighted,
unless the -J option is in effect, in which case
only the status column is highlighted.
-W or --HILITE-UNREAD
-x9,17 will set tabs at positions 9, 17, 25, 33,
etc. The default for n is 8.
-X or --no-init
Disables sending the termcap initialization and
deinitialization strings to the terminal. This is
sometimes desirable if the deinitialization string
does something unnecessary, like clearing the
screen.
--no-keypad
Disables sending the keypad initialization and
deinitialization strings to the terminal. This is
sometimes useful if the keypad strings make the
numeric keypad behave in an undesirable manner.
-yn or --max-forw-scroll=n
Specifies a maximum number of lines to scroll for
ward. If it is necessary to scroll forward more
than n lines, the screen is repainted instead. The
-c or -C option may be used to repaint from the top
of the screen if desired. By default, any forward
movement causes scrolling.
-[z]n or --window=n
Changes the default scrolling window size to n
lines. The default is one screenful. The z and w
commands can also be used to change the window
size. The "z" may be omitted for compatibility
with more. If the number n is negative, it indi
cates n lines less than the current screen size.
For example, if the screen is 24 lines, -z-4 sets
the scrolling window to 20 lines. If the screen is
resized to 40 lines, the scrolling window automati
cally changes to 36 lines.
-Z Causes to give priority to the SJIS over the UJIS
if a "japanese" was selected by the JLESSCHARSET
environment variable. The default value is to give
priority to the UJIS over the SJIS.
-"cc or --quotes=cc
Changes the filename quoting character. This may
be necessary if you are trying to name a file which
contains both spaces and quote characters. Fol
lowed by a single character, this changes the quote
character to that character. Filenames containing
a space should then be surrounded by that character
rather than by double quotes. Followed by two
characters, changes the open quote to the first
character, and the close quote to the second char
acter. Filenames containing a space should then be
the default number of positions to one half of the
screen width.
-- A command line argument of "--" marks the end of
option arguments. Any arguments following this are
interpreted as filenames. This can be useful when
viewing a file whose name begins with a "-" or "+".
+ If a command line option begins with +, the remain
der of that option is taken to be an initial com
mand 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 dis
play 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.
LINE EDITING
When entering command line at the bottom of the screen
(for example, a filename for the :e command, or the pat
tern for a search command), certain keys can be used to
manipulate the command line. Most commands have an alter
nate 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.
HOME [ ESC-0 ]
Move the cursor to the beginning of the line.
^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.
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 direc
tory, 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 [ ESC-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) or ESC (MS-DOS)
Delete the entire command line, or cancel the com
mand if the command line is empty. If you have
changed your line-kill character in Unix to some
thing other than ^U, that character is used instead
of ^U.
KEY BINDINGS
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 "$HOME/.less". On
MS-DOS and Windows systems, less looks for a lesskey file
called "$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 sys
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 file
name, 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 environ
ment 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 origi
nal 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
lessclose.sh:
#! /bin/sh
rm $2
To use these scripts, put them both where they can be exe
cuted and set LESSOPEN="lessopen.sh %s", and LESS
CLOSE="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 pre
processor 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
variable. Possible values for them are:
ascii BS, TAB, NL, CR, and formfeed are control charac
ters, 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 LESS
CHARSET=IBM-1047 or LC_CTYPE=en_US in your environ
ment.
koi8-r Selects a Russian character set.
next Selects a character set appropriate for NeXT com
puters.
utf-8 Selects the UTF-8 encoding of the ISO 10646 charac
ter set.
And possible values for only JLESSCHARSET are:
iso7 Multi character sets with the ISO 2022 code exten
sion techniques in 7 bits are assumed. Characters
with values between 128 and 255 are treated as
binary. The level of implementation of Less is
level 3 of ISO 2022.
iso8 Multi character sets with the ISO 2022 code exten
sion techniques in 8 bits are assumed. The level
of implementation of Less is level 3 of ISO 2022.
jis Only Japanese character sets with the ISO 2022 code
extension techniques in 7 bits are assumed.
ujis If characters has values between 32 and 127, the
ASCII character set are assumed. If characters has
values between 162 and 254, the JISX 0208 character
japanese
All Japanese character sets, jis, ujis and sjis,
are assumed. But less output only the jis.
Japanese has several code sets (not character sets). Thus
less must convert among them to display them correctly.
Possible values with this conversion for only JLESSCHARSET
are:
ujis-iso7
The ujis and iso7 are assumend. But less output
only the iso7.
euc-iso7
Same as ujis-iso7.
sjis-iso7
The sjis and iso7 are assumend. But less output
only the iso7.
ujis-jis
The ujis and jis are assumend. But less output
only the jis.
euc-jis
Same as ujis-jis.
sjis-jis
The sjis and jis are assumend. But less output
only the jis.
jis-ujis
The jis and ujis are assumend. But less output
only the ujis.
jis-euc
Same as jis-ujis.
jis-sjis
The jis and sjis are assumend. But less output
only the sjis.
japanese-iso7
The japanese and iso7 are assumend. But less out
put only the iso7.
japanese-jis
The japanese is assumend. But less output only the
jis. Same as japanese.
japanese-ujis
The japanese is assumend. But less output only the
Same as ujis-sjis.
sjis-ujis
The sjis is assumend. But less output only the
ujis.
sjis-euc
Same as sjis-ujis.
Other way to select a character set is to use the LANG
environment variable. If it start with "ja_JP" or
"japan", less read all Japanese coded characters as some
Japanese character set, and a rest of the LANG environment
variable specify output coding.
The ISO 2022 code extension techniques define 4 planes to
display many character sets easy. Default setting of
planes is selected by the JLESSPLANESET environment vari
able. If the JLESSPLANESET vriable is equal to
"japanese", "ujis" or "euc", less treat g1 plane as JISX
0208, g2 plane as JISX 0201 right half, g3 plane as JISX
0212. If it is equal to "latin1", "latin2", "latin3",
"latin4", "greek", "arabic", "hebrew", "cyrillic" or
"latin5", less treat g1 plane as one of ISO 8859. Other
wise, less try to parse the JLESSPLANESET variable as real
escape sequences for setting up, and "\e" in JLESSPLANESET
is treated as escape code when parsing.
Less understand almost all escape sequence about character
set in the ISO 2022 code extension techniques. There are
many escape sequences to select the character set. On the
one hand, less output only 6 escape sequences to select a
character set: '^[(', '^[-', '^[$(', '^[$-', '^N' and
'^O'. It means less is friendly to a terminal and a ter
minal emulator.
And there is special "character set" for keyboard inputs.
The JLESSKEYCHARSET environment variable is used for such
purpose. Possible values of it are equal to the JLESS
CHARSET environment variable.
In special cases, it may be desired to tailor less to use
a character set other than the ones definable by LESS
CHARSET. In this case, the environment variable LESS
CHARDEF can be used to define a character set. It should
be set to a string where each character in the string rep
resents 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 repeti
tion. 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
koi8-r 8bcccbcc18b95.b128.
latin1 8bcccbcc18b95.33b.
next 8bcccbcc18b95.bb125.bb
If neither LESSCHARSET nor LESSCHARDEF is set, but the
string "UTF-8" is found in the LC_ALL, LC_TYPE or 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 or 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 vari
able. 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 LESS
BINFMT is "*u[%x]", binary characters are displayed in
underlined hexadecimal surrounded by brackets. The
default if no LESSBINFMT is specified is "*s<%X>".
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 ordi
nary 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
%D Replaced by the number of pages in the input file,
or 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, or the EDITOR environment
variable if VISUAL is not defined). See the dis
cussion 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 any
where.
%x Replaced by the name of the next input file in the
list.
%K Replaced by the name of the last non ASCII charac
ter set or code set.
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 sin
gle character acts like an "IF": depending on the follow
ing character, a condition is evaluated. If the condition
is true, any characters following the question mark and
?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:-...
next file, if there is one. Finally, any trailing spaces
are truncated. This is the default prompt. For refer
ence, 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 com
mand 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 vari
able 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
take precedence over variables defined in the system-wide
lesskey file.
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 or 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 envi
ronment 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.
JLESS same as the LESS environment variable.
LESSANSIENDCHARS
Characters which are assumed to end an ANSI color
escape sequence (default "m").
LESSBINFMT
Format for displaying non-printable, non-control
characters.
LESSCHARDEF
Defines a character set.
JLESSCHARSET
Selects a predefined character set.
LESSCHARSET
Selects a predefined character set if JLESSCHARSET
is not defined.
Name of the lessecho program (default "lessecho").
The lessecho program is needed to expand metachar
acters, such as * and ?, in filenames on Unix sys
tems.
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.
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 "metachar
acters" by the shell.
LESSMETAESCAPE
Prefix which less will add before each metacharac
ter in a command sent to the shell. If LESS
METAESCAPE is an empty string, commands containing
metacharacters will not be passed to the shell.
LESSOPEN
Command line to invoke the (optional) input-prepro
cessor.
LESSSECURE
Runs less in "secure" mode. See discussion under
SECURITY.
LESSSEPARATOR
String to be appended to a directory name in file
name completion.
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
WARNINGS
The = command and prompts (unless changed by -P) report
the line numbers of the lines at the top and bottom of the
screen, but the byte and percent of the line after the one
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 dis
abled 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.)
When viewing text containing ANSI color escape sequences
using the -R option, searching will not find text contain
ing an embedded escape sequence. Also, search highlight
ing may change the color of some of the text which follows
the highlighted text.
On some systems, setlocale claims that ASCII characters 0
thru 31 are control characters rather than binary charac
ters. 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).
See http://www.greenwoodsoftware.com/less for the latest
list of known bugs in this version of less.
COPYRIGHT
Copyright (C) 2002 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
http://www.greenwoodsoftware.com/less.
PATCH
Copyright (c) 1994-2000 Kazushi (Jam) Marukawa, Japanized
routines only
Comments about this part to: jam@pobox.com
You may distribute under the terms of the Less License.
Version 381: 17 Jan 2003 LESS(1)
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